diff --git a/DRAMSys/library/src/controller/checker/CheckerDDR3.cpp b/DRAMSys/library/src/controller/checker/CheckerDDR3.cpp
index 57687072..1e48ea04 100644
--- a/DRAMSys/library/src/controller/checker/CheckerDDR3.cpp
+++ b/DRAMSys/library/src/controller/checker/CheckerDDR3.cpp
@@ -42,11 +42,11 @@ CheckerDDR3::CheckerDDR3()
         SC_REPORT_FATAL("CheckerDDR3", "Wrong MemSpec chosen");
 
     lastScheduledByCommandAndBank = std::vector<std::vector<sc_time>>
-            (numberOfCommands(), std::vector<sc_time>(memSpec->numberOfBanks));
+            (numberOfCommands(), std::vector<sc_time>(memSpec->numberOfBanks, sc_max_time()));
     lastScheduledByCommandAndRank = std::vector<std::vector<sc_time>>
-            (numberOfCommands(), std::vector<sc_time>(memSpec->numberOfRanks));
-    lastScheduledByCommand = std::vector<sc_time>(numberOfCommands());
-
+            (numberOfCommands(), std::vector<sc_time>(memSpec->numberOfRanks, sc_max_time()));
+    lastScheduledByCommand = std::vector<sc_time>(numberOfCommands(), sc_max_time());
+    lastCommandOnBus = sc_max_time();
     last4Activates = std::vector<std::queue<sc_time>>(memSpec->numberOfRanks);
 
     tBURST = memSpec->burstLength / memSpec->dataRate * memSpec->tCK;
@@ -68,142 +68,142 @@ sc_time CheckerDDR3::timeToSatisfyConstraints(Command command, Rank rank, BankGr
     if (command == Command::RD || command == Command::RDA)
     {
         lastCommandStart = lastScheduledByCommandAndBank[Command::ACT][bank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRCD - memSpec->tAL);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::RD][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tCCD);
 
-        lastCommandStart = lastScheduledByCommand[Command::RD] != lastScheduledByCommandAndRank[Command::RD][rank.ID()] ? lastScheduledByCommand[Command::RD] : SC_ZERO_TIME;
-        if (lastCommandStart != SC_ZERO_TIME)
+        lastCommandStart = lastScheduledByCommand[Command::RD] != lastScheduledByCommandAndRank[Command::RD][rank.ID()] ? lastScheduledByCommand[Command::RD] : sc_max_time();
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tBURST + memSpec->tRTRS);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::RDA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tCCD);
 
-        lastCommandStart = lastScheduledByCommand[Command::RDA] != lastScheduledByCommandAndRank[Command::RDA][rank.ID()] ? lastScheduledByCommand[Command::RDA] : SC_ZERO_TIME;
-        if (lastCommandStart != SC_ZERO_TIME)
+        lastCommandStart = lastScheduledByCommand[Command::RDA] != lastScheduledByCommandAndRank[Command::RDA][rank.ID()] ? lastScheduledByCommand[Command::RDA] : sc_max_time();
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tBURST + memSpec->tRTRS);
 
         if (command == Command::RDA)
         {
             lastCommandStart = lastScheduledByCommandAndBank[Command::WR][bank.ID()];
-            if (lastCommandStart != SC_ZERO_TIME)
+            if (lastCommandStart != sc_max_time())
                 earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRPRE - memSpec->tRTP);
         }
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::WR][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRRD);
 
         lastCommandStart = lastScheduledByCommand[Command::WR];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRRD_R);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::WRA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRRD);
 
         lastCommandStart = lastScheduledByCommand[Command::WRA];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRRD_R);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PDXA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXP);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::SREFEX][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXSDLL);
     }
     else if (command == Command::WR || command == Command::WRA)
     {
         lastCommandStart = lastScheduledByCommandAndBank[Command::ACT][bank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRCD - memSpec->tAL);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::RD][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tRDWR);
 
-        lastCommandStart = lastScheduledByCommand[Command::RD] != lastScheduledByCommandAndRank[Command::RD][rank.ID()] ? lastScheduledByCommand[Command::RD] : SC_ZERO_TIME;
-        if (lastCommandStart != SC_ZERO_TIME)
+        lastCommandStart = lastScheduledByCommand[Command::RD] != lastScheduledByCommandAndRank[Command::RD][rank.ID()] ? lastScheduledByCommand[Command::RD] : sc_max_time();
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tRDWR_R);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::RDA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tRDWR);
 
-        lastCommandStart = lastScheduledByCommand[Command::RDA] != lastScheduledByCommandAndRank[Command::RDA][rank.ID()] ? lastScheduledByCommand[Command::RDA] : SC_ZERO_TIME;
-        if (lastCommandStart != SC_ZERO_TIME)
+        lastCommandStart = lastScheduledByCommand[Command::RDA] != lastScheduledByCommandAndRank[Command::RDA][rank.ID()] ? lastScheduledByCommand[Command::RDA] : sc_max_time();
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tRDWR_R);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::WR][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tCCD);
 
-        lastCommandStart = lastScheduledByCommand[Command::WR] != lastScheduledByCommandAndRank[Command::WR][rank.ID()] ? lastScheduledByCommand[Command::WR] : SC_ZERO_TIME;
-        if (lastCommandStart != SC_ZERO_TIME)
+        lastCommandStart = lastScheduledByCommand[Command::WR] != lastScheduledByCommandAndRank[Command::WR][rank.ID()] ? lastScheduledByCommand[Command::WR] : sc_max_time();
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tBURST + memSpec->tRTRS);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::WRA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tCCD);
 
-        lastCommandStart = lastScheduledByCommand[Command::WRA] != lastScheduledByCommandAndRank[Command::WRA][rank.ID()] ? lastScheduledByCommand[Command::WRA] : SC_ZERO_TIME;
-        if (lastCommandStart != SC_ZERO_TIME)
+        lastCommandStart = lastScheduledByCommand[Command::WRA] != lastScheduledByCommandAndRank[Command::WRA][rank.ID()] ? lastScheduledByCommand[Command::WRA] : sc_max_time();
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tBURST + memSpec->tRTRS);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PDXA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXP);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::SREFEX][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXSDLL);
     }
     else if (command == Command::ACT)
     {
         lastCommandStart = lastScheduledByCommandAndBank[Command::ACT][bank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRC);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::ACT][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRRD);
 
         lastCommandStart = lastScheduledByCommandAndBank[Command::RDA][bank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tAL + memSpec->tRTP + memSpec->tRP);
 
         lastCommandStart = lastScheduledByCommandAndBank[Command::WRA][bank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRPRE + memSpec->tRP);
 
         lastCommandStart = lastScheduledByCommandAndBank[Command::PRE][bank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRP);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PREA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRP);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PDXA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXP);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PDXP][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXP);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::REFA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRFC);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::SREFEX][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXS);
 
         if (last4Activates[rank.ID()].size() >= 4)
@@ -212,201 +212,202 @@ sc_time CheckerDDR3::timeToSatisfyConstraints(Command command, Rank rank, BankGr
     else if (command == Command::PRE)
     {
         lastCommandStart = lastScheduledByCommandAndBank[Command::ACT][bank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRAS);
 
         lastCommandStart = lastScheduledByCommandAndBank[Command::RD][bank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tAL + memSpec->tRTP);
 
         lastCommandStart = lastScheduledByCommandAndBank[Command::WR][bank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRPRE);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PDXA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXP);
     }
     else if (command == Command::PREA)
     {
         lastCommandStart = lastScheduledByCommandAndRank[Command::ACT][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRAS);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::RD][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tAL + memSpec->tRTP);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::RDA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tAL + memSpec->tRTP);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::WR][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRPRE);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::WRA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRPRE);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PDXA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXP);
     }
     else if (command == Command::REFA)
     {
         lastCommandStart = lastScheduledByCommandAndRank[Command::ACT][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRC);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::RDA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tAL + memSpec->tRTP + memSpec->tRP);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::WRA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRPRE + memSpec->tRP);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PRE][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRP);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PREA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRP);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PDXP][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXP);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::REFA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRFC);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::SREFEX][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXS);
     }
     else if (command == Command::PDEA)
     {
         lastCommandStart = lastScheduledByCommandAndRank[Command::ACT][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tACTPDEN);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::RD][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tRDPDEN);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::RDA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tRDPDEN);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::WR][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRPDEN);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::WRA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRAPDEN);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PRE][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tPRPDEN);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PDXA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tCKE);
     }
     else if (command == Command::PDXA)
     {
         lastCommandStart = lastScheduledByCommandAndRank[Command::PDEA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tPD);
     }
     else if (command == Command::PDEP)
     {
         lastCommandStart = lastScheduledByCommandAndRank[Command::RD][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tRDPDEN);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::RDA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tRDPDEN);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::WRA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRAPDEN);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PRE][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tPRPDEN);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PREA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tPRPDEN);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PDXP][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tCKE);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::REFA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tREFPDEN);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::SREFEX][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXS);
     }
     else if (command == Command::PDXP)
     {
         lastCommandStart = lastScheduledByCommandAndRank[Command::PDEP][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tPD);
     }
     else if (command == Command::SREFEN)
     {
         lastCommandStart = lastScheduledByCommandAndRank[Command::ACT][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRC);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::RDA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + std::max(tRDPDEN, memSpec->tAL + memSpec->tRTP + memSpec->tRP));
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::WRA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + std::max(tWRAPDEN, tWRPRE + memSpec->tRP));
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PRE][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRP);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PREA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRP);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PDXP][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXP);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::REFA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRFC);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::SREFEX][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXS);
     }
     else if (command == Command::SREFEX)
     {
         lastCommandStart = lastScheduledByCommandAndRank[Command::SREFEN][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tCKESR);
     }
     else
         SC_REPORT_FATAL("CheckerDDR3", "Unknown command!");
 
-    earliestTimeToStart = std::max(earliestTimeToStart, lastCommandOnBus + memSpec->tCK);
+    if (lastCommandOnBus != sc_max_time())
+        earliestTimeToStart = std::max(earliestTimeToStart, lastCommandOnBus + memSpec->tCK);
 
     return earliestTimeToStart;
 }
diff --git a/DRAMSys/library/src/controller/checker/CheckerDDR4.cpp b/DRAMSys/library/src/controller/checker/CheckerDDR4.cpp
index 5883dcf9..1dad1943 100644
--- a/DRAMSys/library/src/controller/checker/CheckerDDR4.cpp
+++ b/DRAMSys/library/src/controller/checker/CheckerDDR4.cpp
@@ -42,13 +42,13 @@ CheckerDDR4::CheckerDDR4()
         SC_REPORT_FATAL("CheckerDDR4", "Wrong MemSpec chosen");
 
     lastScheduledByCommandAndBank = std::vector<std::vector<sc_time>>
-            (numberOfCommands(), std::vector<sc_time>(memSpec->numberOfBanks));
+            (numberOfCommands(), std::vector<sc_time>(memSpec->numberOfBanks, sc_max_time()));
     lastScheduledByCommandAndBankGroup = std::vector<std::vector<sc_time>>
-            (numberOfCommands(), std::vector<sc_time>(memSpec->numberOfBankGroups));
+            (numberOfCommands(), std::vector<sc_time>(memSpec->numberOfBankGroups, sc_max_time()));
     lastScheduledByCommandAndRank = std::vector<std::vector<sc_time>>
-            (numberOfCommands(), std::vector<sc_time>(memSpec->numberOfRanks));
-    lastScheduledByCommand = std::vector<sc_time>(numberOfCommands());
-
+            (numberOfCommands(), std::vector<sc_time>(memSpec->numberOfRanks, sc_max_time()));
+    lastScheduledByCommand = std::vector<sc_time>(numberOfCommands(), sc_max_time());
+    lastCommandOnBus = sc_max_time();
     last4Activates = std::vector<std::queue<sc_time>>(memSpec->numberOfRanks);
 
     tBURST = memSpec->burstLength / memSpec->dataRate * memSpec->tCK;
@@ -71,170 +71,170 @@ sc_time CheckerDDR4::timeToSatisfyConstraints(Command command, Rank rank, BankGr
     if (command == Command::RD || command == Command::RDA)
     {
         lastCommandStart = lastScheduledByCommandAndBank[Command::ACT][bank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRCD - memSpec->tAL);
 
         lastCommandStart = lastScheduledByCommandAndBankGroup[Command::RD][bankgroup.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tCCD_L);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::RD][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tCCD_S);
 
-        lastCommandStart = lastScheduledByCommand[Command::RD] != lastScheduledByCommandAndRank[Command::RD][rank.ID()] ? lastScheduledByCommand[Command::RD] : SC_ZERO_TIME;
-        if (lastCommandStart != SC_ZERO_TIME)
+        lastCommandStart = lastScheduledByCommand[Command::RD] != lastScheduledByCommandAndRank[Command::RD][rank.ID()] ? lastScheduledByCommand[Command::RD] : sc_max_time();
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tBURST + memSpec->tRTRS);
 
         lastCommandStart = lastScheduledByCommandAndBankGroup[Command::RDA][bankgroup.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tCCD_L);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::RDA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tCCD_S);
 
-        lastCommandStart = lastScheduledByCommand[Command::RDA] != lastScheduledByCommandAndRank[Command::RDA][rank.ID()] ? lastScheduledByCommand[Command::RDA] : SC_ZERO_TIME;
-        if (lastCommandStart != SC_ZERO_TIME)
+        lastCommandStart = lastScheduledByCommand[Command::RDA] != lastScheduledByCommandAndRank[Command::RDA][rank.ID()] ? lastScheduledByCommand[Command::RDA] : sc_max_time();
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tBURST + memSpec->tRTRS);
 
         if (command == Command::RDA)
         {
             lastCommandStart = lastScheduledByCommandAndBank[Command::WR][bank.ID()];
-            if (lastCommandStart != SC_ZERO_TIME)
+            if (lastCommandStart != sc_max_time())
                 earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRPRE - memSpec->tRTP);
         }
 
         lastCommandStart = lastScheduledByCommandAndBankGroup[Command::WR][bankgroup.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRRD_L);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::WR][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRRD_S);
 
         lastCommandStart = lastScheduledByCommand[Command::WR];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRRD_R);
 
         lastCommandStart = lastScheduledByCommandAndBankGroup[Command::WRA][bankgroup.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRRD_L);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::WRA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRRD_S);
 
         lastCommandStart = lastScheduledByCommand[Command::WRA];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRRD_R);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PDXA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXP);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::SREFEX][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXSDLL);
     }
     else if (command == Command::WR || command == Command::WRA)
     {
         lastCommandStart = lastScheduledByCommandAndBank[Command::ACT][bank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRCD - memSpec->tAL);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::RD][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tRDWR);
 
-        lastCommandStart = lastScheduledByCommand[Command::RD] != lastScheduledByCommandAndRank[Command::RD][rank.ID()] ? lastScheduledByCommand[Command::RD] : SC_ZERO_TIME;
-        if (lastCommandStart != SC_ZERO_TIME)
+        lastCommandStart = lastScheduledByCommand[Command::RD] != lastScheduledByCommandAndRank[Command::RD][rank.ID()] ? lastScheduledByCommand[Command::RD] : sc_max_time();
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tRDWR_R);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::RDA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tRDWR);
 
-        lastCommandStart = lastScheduledByCommand[Command::RDA] != lastScheduledByCommandAndRank[Command::RDA][rank.ID()] ? lastScheduledByCommand[Command::RDA] : SC_ZERO_TIME;
-        if (lastCommandStart != SC_ZERO_TIME)
+        lastCommandStart = lastScheduledByCommand[Command::RDA] != lastScheduledByCommandAndRank[Command::RDA][rank.ID()] ? lastScheduledByCommand[Command::RDA] : sc_max_time();
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tRDWR_R);
 
         lastCommandStart = lastScheduledByCommandAndBankGroup[Command::WR][bankgroup.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tCCD_L);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::WR][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tCCD_S);
 
-        lastCommandStart = lastScheduledByCommand[Command::WR] != lastScheduledByCommandAndRank[Command::WR][rank.ID()] ? lastScheduledByCommand[Command::WR] : SC_ZERO_TIME;
-        if (lastCommandStart != SC_ZERO_TIME)
+        lastCommandStart = lastScheduledByCommand[Command::WR] != lastScheduledByCommandAndRank[Command::WR][rank.ID()] ? lastScheduledByCommand[Command::WR] : sc_max_time();
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tBURST + memSpec->tRTRS);
 
         lastCommandStart = lastScheduledByCommandAndBankGroup[Command::WRA][bankgroup.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tCCD_L);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::WRA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tCCD_S);
 
-        lastCommandStart = lastScheduledByCommand[Command::WRA] != lastScheduledByCommandAndRank[Command::WRA][rank.ID()] ? lastScheduledByCommand[Command::WRA] : SC_ZERO_TIME;
-        if (lastCommandStart != SC_ZERO_TIME)
+        lastCommandStart = lastScheduledByCommand[Command::WRA] != lastScheduledByCommandAndRank[Command::WRA][rank.ID()] ? lastScheduledByCommand[Command::WRA] : sc_max_time();
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tBURST + memSpec->tRTRS);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PDXA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXP);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::SREFEX][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXSDLL);
     }
     else if (command == Command::ACT)
     {
         lastCommandStart = lastScheduledByCommandAndBank[Command::ACT][bank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRC);
 
         lastCommandStart = lastScheduledByCommandAndBankGroup[Command::ACT][bankgroup.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRRD_L);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::ACT][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRRD_S);
 
         lastCommandStart = lastScheduledByCommandAndBank[Command::RDA][bank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tAL + memSpec->tRTP + memSpec->tRP);
 
         lastCommandStart = lastScheduledByCommandAndBank[Command::WRA][bank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRPRE + memSpec->tRP);
 
         lastCommandStart = lastScheduledByCommandAndBank[Command::PRE][bank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRP);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PREA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRP);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PDXA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXP);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PDXP][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXP);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::REFA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRFC);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::SREFEX][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXS);
 
         if (last4Activates[rank.ID()].size() >= 4)
@@ -243,201 +243,202 @@ sc_time CheckerDDR4::timeToSatisfyConstraints(Command command, Rank rank, BankGr
     else if (command == Command::PRE)
     {
         lastCommandStart = lastScheduledByCommandAndBank[Command::ACT][bank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRAS);
 
         lastCommandStart = lastScheduledByCommandAndBank[Command::RD][bank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tAL + memSpec->tRTP);
 
         lastCommandStart = lastScheduledByCommandAndBank[Command::WR][bank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRPRE);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PDXA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXP);
     }
     else if (command == Command::PREA)
     {
         lastCommandStart = lastScheduledByCommandAndRank[Command::ACT][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRAS);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::RD][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tAL + memSpec->tRTP);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::RDA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tAL + memSpec->tRTP);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::WR][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRPRE);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::WRA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRPRE);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PDXA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXP);
     }
     else if (command == Command::REFA)
     {
         lastCommandStart = lastScheduledByCommandAndRank[Command::ACT][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRC);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::RDA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tAL + memSpec->tRTP + memSpec->tRP);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::WRA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRPRE + memSpec->tRP);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PRE][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRP);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PREA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRP);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PDXP][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXP);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::REFA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRFC);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::SREFEX][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXS);
     }
     else if (command == Command::PDEA)
     {
         lastCommandStart = lastScheduledByCommandAndRank[Command::ACT][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tACTPDEN);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::RD][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tRDPDEN);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::RDA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tRDPDEN);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::WR][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRPDEN);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::WRA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRAPDEN);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PRE][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tPRPDEN);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PDXA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tCKE);
     }
     else if (command == Command::PDXA)
     {
         lastCommandStart = lastScheduledByCommandAndRank[Command::PDEA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tPD);
     }
     else if (command == Command::PDEP)
     {
         lastCommandStart = lastScheduledByCommandAndRank[Command::RD][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tRDPDEN);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::RDA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tRDPDEN);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::WRA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRAPDEN);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PRE][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tPRPDEN);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PREA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tPRPDEN);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PDXP][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tCKE);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::REFA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tREFPDEN);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::SREFEX][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXS);
     }
     else if (command == Command::PDXP)
     {
         lastCommandStart = lastScheduledByCommandAndRank[Command::PDEP][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tPD);
     }
     else if (command == Command::SREFEN)
     {
         lastCommandStart = lastScheduledByCommandAndRank[Command::ACT][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRC);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::RDA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + std::max(tRDPDEN, memSpec->tAL + memSpec->tRTP + memSpec->tRP));
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::WRA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + std::max(tWRAPDEN, tWRPRE + memSpec->tRP));
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PRE][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRP);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PREA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRP);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PDXP][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXP);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::REFA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRFC);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::SREFEX][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXS);
     }
     else if (command == Command::SREFEX)
     {
         lastCommandStart = lastScheduledByCommandAndRank[Command::SREFEN][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tCKESR);
     }
     else
         SC_REPORT_FATAL("CheckerDDR4", "Unknown command!");
 
-    earliestTimeToStart = std::max(earliestTimeToStart, lastCommandOnBus + memSpec->tCK);
+    if (lastCommandOnBus != sc_max_time())
+        earliestTimeToStart = std::max(earliestTimeToStart, lastCommandOnBus + memSpec->tCK);
 
     return earliestTimeToStart;
 }
diff --git a/DRAMSys/library/src/controller/checker/CheckerDDR5.cpp b/DRAMSys/library/src/controller/checker/CheckerDDR5.cpp
index 79d6264a..a5458a3d 100644
--- a/DRAMSys/library/src/controller/checker/CheckerDDR5.cpp
+++ b/DRAMSys/library/src/controller/checker/CheckerDDR5.cpp
@@ -42,21 +42,20 @@ CheckerDDR5::CheckerDDR5()
         SC_REPORT_FATAL("CheckerDDR5", "Wrong MemSpec chosen");
 
     lastScheduledByCommandAndDIMMRank = std::vector<std::vector<sc_time>>
-            (numberOfCommands(), std::vector<sc_time>(memSpec->numberOfDIMMRanks));
+            (numberOfCommands(), std::vector<sc_time>(memSpec->numberOfDIMMRanks, sc_max_time()));
     lastScheduledByCommandAndPhysicalRank = std::vector<std::vector<sc_time>>
-            (numberOfCommands(), std::vector<sc_time>(memSpec->numberOfPhysicalRanks));
+            (numberOfCommands(), std::vector<sc_time>(memSpec->numberOfPhysicalRanks, sc_max_time()));
     lastScheduledByCommandAndLogicalRank = std::vector<std::vector<sc_time>>
-            (numberOfCommands(), std::vector<sc_time>(memSpec->numberOfLogicalRanks));
+            (numberOfCommands(), std::vector<sc_time>(memSpec->numberOfLogicalRanks, sc_max_time()));
     lastScheduledByCommandAndBankGroup = std::vector<std::vector<sc_time>>
-            (numberOfCommands(), std::vector<sc_time>(memSpec->numberOfBankGroups));
+            (numberOfCommands(), std::vector<sc_time>(memSpec->numberOfBankGroups, sc_max_time()));
     lastScheduledByCommandAndBank = std::vector<std::vector<sc_time>>
-            (numberOfCommands(), std::vector<sc_time>(memSpec->numberOfBanks));
-    lastScheduledByCommand = std::vector<sc_time>(numberOfCommands());
-
+            (numberOfCommands(), std::vector<sc_time>(memSpec->numberOfBanks, sc_max_time()));
+    lastScheduledByCommand = std::vector<sc_time>(numberOfCommands(), sc_max_time());
     // Required for Same Bank Refresh
-    lastScheduledByCommandAndBankInGroup = std::vector<std::vector<sc_time>>
-            (numberOfCommands(), std::vector<sc_time>(memSpec->numberOfRanks * memSpec->banksPerGroup));
-
+    lastScheduledByCommandAndBankInGroup = std::vector<std::vector<sc_time>>(numberOfCommands(),
+            std::vector<sc_time>(memSpec->numberOfRanks * memSpec->banksPerGroup, sc_max_time()));
+    lastCommandOnBus = sc_max_time();
     last4ActivatesLogical = std::vector<std::queue<sc_time>>(memSpec->numberOfLogicalRanks);
     last4ActivatesPhysical = std::vector<std::queue<sc_time>>(memSpec->numberOfPhysicalRanks);
 
@@ -104,19 +103,19 @@ sc_time CheckerDDR5::timeToSatisfyConstraints(Command command, Rank rank, BankGr
     if (command == Command::RD || command == Command::RDA)
     {
         lastCommandStart = lastScheduledByCommandAndBank[Command::ACT][bank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRCD);
 
         lastCommandStart = lastScheduledByCommandAndBankGroup[Command::RD][bankgroup.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tCCD_L_slr);
 
         lastCommandStart = lastScheduledByCommandAndLogicalRank[Command::RD][logicalrank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tCCD_S_slr);
 
         lastCommandStart = lastScheduledByCommandAndPhysicalRank[Command::RD][physicalrank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tCCD_dlr);
 
         lastCommandStart = lastScheduledByCommand[Command::RD];
@@ -129,15 +128,15 @@ sc_time CheckerDDR5::timeToSatisfyConstraints(Command command, Rank rank, BankGr
         }
 
         lastCommandStart = lastScheduledByCommandAndBankGroup[Command::RDA][bankgroup.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tCCD_L_slr);
 
         lastCommandStart = lastScheduledByCommandAndLogicalRank[Command::RDA][logicalrank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tCCD_S_slr);
 
         lastCommandStart = lastScheduledByCommandAndPhysicalRank[Command::RDA][physicalrank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tCCD_dlr);
 
         lastCommandStart = lastScheduledByCommand[Command::RDA];
@@ -152,20 +151,20 @@ sc_time CheckerDDR5::timeToSatisfyConstraints(Command command, Rank rank, BankGr
         if (command == Command::RDA)
         {
             lastCommandStart = lastScheduledByCommandAndBank[Command::WR][bank.ID()];
-            if (lastCommandStart != SC_ZERO_TIME)
+            if (lastCommandStart != sc_max_time())
                 earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRRDA);
         }
 
         lastCommandStart = lastScheduledByCommandAndBankGroup[Command::WR][bankgroup.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tCCD_L_WTR_slr);
 
         lastCommandStart = lastScheduledByCommandAndLogicalRank[Command::WR][logicalrank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tCCD_S_WTR_slr);
 
         lastCommandStart = lastScheduledByCommandAndPhysicalRank[Command::WR][physicalrank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tCCD_WTR_dlr);
 
         lastCommandStart = lastScheduledByCommand[Command::WR];
@@ -178,15 +177,15 @@ sc_time CheckerDDR5::timeToSatisfyConstraints(Command command, Rank rank, BankGr
         }
 
         lastCommandStart = lastScheduledByCommandAndBankGroup[Command::WRA][bankgroup.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tCCD_L_WTR_slr);
 
         lastCommandStart = lastScheduledByCommandAndLogicalRank[Command::WRA][logicalrank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tCCD_S_WTR_slr);
 
         lastCommandStart = lastScheduledByCommandAndPhysicalRank[Command::WRA][physicalrank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tCCD_WTR_dlr);
 
         lastCommandStart = lastScheduledByCommand[Command::WRA];
@@ -201,19 +200,19 @@ sc_time CheckerDDR5::timeToSatisfyConstraints(Command command, Rank rank, BankGr
     else if (command == Command::WR || command == Command::WRA)
     {
         lastCommandStart = lastScheduledByCommandAndBank[Command::ACT][bank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRCD);
 
         lastCommandStart = lastScheduledByCommandAndBankGroup[Command::RD][bankgroup.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tCCD_L_RTW_slr);
 
         lastCommandStart = lastScheduledByCommandAndLogicalRank[Command::RD][logicalrank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tCCD_S_RTW_slr);
 
         lastCommandStart = lastScheduledByCommandAndPhysicalRank[Command::RD][physicalrank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tCCD_RTW_dlr);
 
         lastCommandStart = lastScheduledByCommand[Command::RD];
@@ -226,15 +225,15 @@ sc_time CheckerDDR5::timeToSatisfyConstraints(Command command, Rank rank, BankGr
         }
 
         lastCommandStart = lastScheduledByCommandAndBankGroup[Command::RDA][bankgroup.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tCCD_L_RTW_slr);
 
         lastCommandStart = lastScheduledByCommandAndLogicalRank[Command::RDA][logicalrank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tCCD_S_RTW_slr);
 
         lastCommandStart = lastScheduledByCommandAndPhysicalRank[Command::RDA][physicalrank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tCCD_RTW_dlr);
 
         lastCommandStart = lastScheduledByCommand[Command::RDA];
@@ -247,15 +246,15 @@ sc_time CheckerDDR5::timeToSatisfyConstraints(Command command, Rank rank, BankGr
         }
 
         lastCommandStart = lastScheduledByCommandAndBankGroup[Command::WR][bankgroup.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tCCD_L_WR_slr);
 
         lastCommandStart = lastScheduledByCommandAndLogicalRank[Command::WR][logicalrank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tCCD_S_WR_slr);
 
         lastCommandStart = lastScheduledByCommandAndPhysicalRank[Command::WR][physicalrank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tCCD_WR_dlr);
 
         lastCommandStart = lastScheduledByCommand[Command::WR];
@@ -268,15 +267,15 @@ sc_time CheckerDDR5::timeToSatisfyConstraints(Command command, Rank rank, BankGr
         }
 
         lastCommandStart = lastScheduledByCommandAndBankGroup[Command::WRA][bankgroup.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tCCD_L_WR_slr);
 
         lastCommandStart = lastScheduledByCommandAndLogicalRank[Command::WRA][logicalrank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tCCD_S_WR_slr);
 
         lastCommandStart = lastScheduledByCommandAndPhysicalRank[Command::WRA][physicalrank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tCCD_WR_dlr);
 
         lastCommandStart = lastScheduledByCommand[Command::WRA];
@@ -291,59 +290,59 @@ sc_time CheckerDDR5::timeToSatisfyConstraints(Command command, Rank rank, BankGr
     else if (command == Command::ACT)
     {
         lastCommandStart = lastScheduledByCommandAndBank[Command::ACT][bank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRC);
 
         lastCommandStart = lastScheduledByCommandAndBankGroup[Command::ACT][bankgroup.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRRD_L_slr);
 
         lastCommandStart = lastScheduledByCommandAndLogicalRank[Command::ACT][logicalrank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRRD_S_slr);
 
         lastCommandStart = lastScheduledByCommandAndPhysicalRank[Command::ACT][physicalrank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRRD_dlr);
 
         lastCommandStart = lastScheduledByCommandAndBank[Command::RDA][bank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tRDAACT);
 
         lastCommandStart = lastScheduledByCommandAndBank[Command::WRA][bank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRAACT);
 
         lastCommandStart = lastScheduledByCommandAndBank[Command::PRE][bank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRP - cmdOffset);
 
         lastCommandStart = lastScheduledByCommandAndLogicalRank[Command::PREA][logicalrank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRP - cmdOffset);
 
         lastCommandStart = lastScheduledByCommandAndBankInGroup[Command::PRESB][bankInGroup.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRP - cmdOffset);
 
         lastCommandStart = lastScheduledByCommandAndLogicalRank[Command::REFA][logicalrank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRFC_slr - cmdOffset);
 
         // TODO: No tRFC_dlr and tRFC_dpr between REFA and ACT?
 
         lastCommandStart = lastScheduledByCommandAndBankInGroup[Command::REFSB][bankInGroup.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRFCsb_slr - cmdOffset);
 
         // TODO: No tRFCsb_dlr between REFSB and ACT?
 
         lastCommandStart = lastScheduledByCommandAndLogicalRank[Command::REFSB][logicalrank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tREFSBRD_slr - cmdOffset);
 
         lastCommandStart = lastScheduledByCommandAndPhysicalRank[Command::REFSB][physicalrank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tREFSBRD_dlr - cmdOffset);
 
         if (last4ActivatesLogical[logicalrank.ID()].size() >= 4)
@@ -357,57 +356,57 @@ sc_time CheckerDDR5::timeToSatisfyConstraints(Command command, Rank rank, BankGr
     else if (command == Command::PRE)
     {
         lastCommandStart = lastScheduledByCommandAndBank[Command::ACT][bank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRAS + memSpec->tCK);
 
         lastCommandStart = lastScheduledByCommandAndBank[Command::RD][bank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRTP + memSpec->tCK);
 
         lastCommandStart = lastScheduledByCommandAndBank[Command::WR][bank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRPRE + memSpec->tCK);
 
         lastCommandStart = lastScheduledByCommandAndPhysicalRank[Command::PRE][physicalrank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tPPD);
 
         lastCommandStart = lastScheduledByCommandAndPhysicalRank[Command::PREA][physicalrank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tPPD);
 
         lastCommandStart = lastScheduledByCommandAndPhysicalRank[Command::PRESB][physicalrank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tPPD);
     }
     else if (command == Command::PREA)
     {
         lastCommandStart = lastScheduledByCommandAndLogicalRank[Command::ACT][logicalrank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRAS + memSpec->tCK);
 
         lastCommandStart = lastScheduledByCommandAndLogicalRank[Command::RD][logicalrank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRTP + memSpec->tCK);
 
         lastCommandStart = lastScheduledByCommandAndLogicalRank[Command::RDA][logicalrank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRTP + memSpec->tCK);
 
         lastCommandStart = lastScheduledByCommandAndLogicalRank[Command::WR][logicalrank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRPRE + memSpec->tCK);
 
         lastCommandStart = lastScheduledByCommandAndLogicalRank[Command::WRA][logicalrank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRPRE + memSpec->tCK);
 
         lastCommandStart = lastScheduledByCommandAndPhysicalRank[Command::PRE][physicalrank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tPPD);
 
         lastCommandStart = lastScheduledByCommandAndPhysicalRank[Command::PREA][physicalrank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tPPD);
 
         // PRESB tPPD
@@ -415,67 +414,67 @@ sc_time CheckerDDR5::timeToSatisfyConstraints(Command command, Rank rank, BankGr
     else if (command == Command::PRESB)
     {
         lastCommandStart = lastScheduledByCommandAndBankInGroup[Command::ACT][bankInGroup.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRAS + memSpec->tCK);
 
         lastCommandStart = lastScheduledByCommandAndBankInGroup[Command::RD][bankInGroup.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRTP + memSpec->tCK);
 
         lastCommandStart = lastScheduledByCommandAndBankInGroup[Command::RDA][bankInGroup.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRTP + memSpec->tCK);
 
         lastCommandStart = lastScheduledByCommandAndBankInGroup[Command::WR][bankInGroup.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRPRE + memSpec->tCK);
 
         lastCommandStart = lastScheduledByCommandAndBankInGroup[Command::WRA][bankInGroup.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRPRE + memSpec->tCK);
 
         lastCommandStart = lastScheduledByCommandAndPhysicalRank[Command::PRE][physicalrank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tPPD);
 
         // PREA tRP
 
         lastCommandStart = lastScheduledByCommandAndPhysicalRank[Command::PRESB][physicalrank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tPPD);
     }
     else if (command == Command::REFA)
     {
         lastCommandStart = lastScheduledByCommandAndLogicalRank[Command::ACT][logicalrank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRC + memSpec->tCK);
 
         lastCommandStart = lastScheduledByCommandAndPhysicalRank[Command::RDA][physicalrank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tRDAACT + memSpec->tCK);
 
         lastCommandStart = lastScheduledByCommandAndLogicalRank[Command::WRA][logicalrank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRPRE + memSpec->tRP + memSpec->tCK);
 
         lastCommandStart = lastScheduledByCommandAndLogicalRank[Command::PRE][logicalrank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRP);
 
         lastCommandStart = lastScheduledByCommandAndLogicalRank[Command::PREA][logicalrank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRP);
 
         lastCommandStart = lastScheduledByCommandAndLogicalRank[Command::REFA][logicalrank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRFC_slr);
 
         lastCommandStart = lastScheduledByCommandAndPhysicalRank[Command::REFA][physicalrank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRFC_dlr);
 
         lastCommandStart = lastScheduledByCommandAndDIMMRank[Command::REFA][dimmrank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRFC_dpr);
 
         // REFSB tRFCsb_slr/dlr
@@ -484,51 +483,51 @@ sc_time CheckerDDR5::timeToSatisfyConstraints(Command command, Rank rank, BankGr
     else if (command == Command::REFSB)
     {
         lastCommandStart = lastScheduledByCommandAndBankInGroup[Command::ACT][bankInGroup.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRC + memSpec->tCK);
 
         lastCommandStart = lastScheduledByCommandAndLogicalRank[Command::ACT][logicalrank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRRD_L_slr + memSpec->tCK);
 
         lastCommandStart = lastScheduledByCommandAndBankInGroup[Command::RDA][bankInGroup.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tRDAACT + memSpec->tCK);
 
         lastCommandStart = lastScheduledByCommandAndBankInGroup[Command::WRA][bankInGroup.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRAACT + memSpec->tCK);
 
         lastCommandStart = lastScheduledByCommandAndBankInGroup[Command::PRE][bankInGroup.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRP);
 
         // PREA tRP
 
         lastCommandStart = lastScheduledByCommandAndBankInGroup[Command::PRESB][bankInGroup.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRP);
 
         lastCommandStart = lastScheduledByCommandAndLogicalRank[Command::REFA][logicalrank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRFC_slr);
 
         // TODO: check this
         lastCommandStart = lastScheduledByCommandAndPhysicalRank[Command::REFA][physicalrank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRFC_dlr);
 
         // TODO: check this
         lastCommandStart = lastScheduledByCommandAndDIMMRank[Command::REFA][dimmrank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRFC_dpr);
 
         lastCommandStart = lastScheduledByCommandAndLogicalRank[Command::REFSB][logicalrank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRFCsb_slr);
 
         lastCommandStart = lastScheduledByCommandAndPhysicalRank[Command::REFSB][physicalrank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRFCsb_dlr);
 
         if (last4ActivatesLogical[logicalrank.ID()].size() >= 4)
@@ -542,7 +541,8 @@ sc_time CheckerDDR5::timeToSatisfyConstraints(Command command, Rank rank, BankGr
     else
         SC_REPORT_FATAL("CheckerDDR5", "Unknown command!");
 
-    earliestTimeToStart = std::max(earliestTimeToStart, lastCommandOnBus + memSpec->tCK);
+    if (lastCommandOnBus != sc_max_time())
+        earliestTimeToStart = std::max(earliestTimeToStart, lastCommandOnBus + memSpec->tCK);
 
     return earliestTimeToStart;
 }
diff --git a/DRAMSys/library/src/controller/checker/CheckerGDDR5.cpp b/DRAMSys/library/src/controller/checker/CheckerGDDR5.cpp
index d3c5e022..fe5fc00d 100644
--- a/DRAMSys/library/src/controller/checker/CheckerGDDR5.cpp
+++ b/DRAMSys/library/src/controller/checker/CheckerGDDR5.cpp
@@ -42,13 +42,13 @@ CheckerGDDR5::CheckerGDDR5()
         SC_REPORT_FATAL("CheckerGDDR5", "Wrong MemSpec chosen");
 
     lastScheduledByCommandAndBank = std::vector<std::vector<sc_time>>
-            (numberOfCommands(), std::vector<sc_time>(memSpec->numberOfBanks));
+            (numberOfCommands(), std::vector<sc_time>(memSpec->numberOfBanks, sc_max_time()));
     lastScheduledByCommandAndBankGroup = std::vector<std::vector<sc_time>>
-            (numberOfCommands(), std::vector<sc_time>(memSpec->numberOfBankGroups));
+            (numberOfCommands(), std::vector<sc_time>(memSpec->numberOfBankGroups, sc_max_time()));
     lastScheduledByCommandAndRank = std::vector<std::vector<sc_time>>
-            (numberOfCommands(), std::vector<sc_time>(memSpec->numberOfRanks));
-    lastScheduledByCommand = std::vector<sc_time>(numberOfCommands());
-
+            (numberOfCommands(), std::vector<sc_time>(memSpec->numberOfRanks, sc_max_time()));
+    lastScheduledByCommand = std::vector<sc_time>(numberOfCommands(), sc_max_time());
+    lastCommandOnBus = sc_max_time();
     last4Activates = std::vector<std::queue<sc_time>>(memSpec->numberOfRanks);
     last32Activates = std::vector<std::queue<sc_time>>(memSpec->numberOfRanks);
 
@@ -72,178 +72,178 @@ sc_time CheckerGDDR5::timeToSatisfyConstraints(Command command, Rank rank, BankG
     if (command == Command::RD || command == Command::RDA)
     {
         lastCommandStart = lastScheduledByCommandAndBank[Command::ACT][bank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRCDRD);
 
         lastCommandStart = lastScheduledByCommandAndBankGroup[Command::RD][bankgroup.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tCCDL);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::RD][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tCCDS);
 
-        lastCommandStart = lastScheduledByCommand[Command::RD] != lastScheduledByCommandAndRank[Command::RD][rank.ID()] ? lastScheduledByCommand[Command::RD] : SC_ZERO_TIME;
-        if (lastCommandStart != SC_ZERO_TIME)
+        lastCommandStart = lastScheduledByCommand[Command::RD] != lastScheduledByCommandAndRank[Command::RD][rank.ID()] ? lastScheduledByCommand[Command::RD] : sc_max_time();
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tBURST + memSpec->tRTRS);
 
         lastCommandStart = lastScheduledByCommandAndBankGroup[Command::RDA][bankgroup.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tCCDL);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::RDA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tCCDS);
 
-        lastCommandStart = lastScheduledByCommand[Command::RDA] != lastScheduledByCommandAndRank[Command::RDA][rank.ID()] ? lastScheduledByCommand[Command::RDA] : SC_ZERO_TIME;
-        if (lastCommandStart != SC_ZERO_TIME)
+        lastCommandStart = lastScheduledByCommand[Command::RDA] != lastScheduledByCommandAndRank[Command::RDA][rank.ID()] ? lastScheduledByCommand[Command::RDA] : sc_max_time();
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tBURST + memSpec->tRTRS);
 
         if (command == Command::RDA)
         {
             lastCommandStart = lastScheduledByCommandAndBank[Command::WR][bank.ID()];
-            if (lastCommandStart != SC_ZERO_TIME)
+            if (lastCommandStart != sc_max_time())
                 earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRPRE - memSpec->tRTP);
         }
 
         lastCommandStart = lastScheduledByCommandAndBankGroup[Command::WR][bankgroup.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRRD_L);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::WR][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRRD_S);
 
-        lastCommandStart = lastScheduledByCommand[Command::WR] != lastScheduledByCommandAndRank[Command::WR][rank.ID()] ? lastScheduledByCommand[Command::WR] : SC_ZERO_TIME;
-        if (lastCommandStart != SC_ZERO_TIME)
+        lastCommandStart = lastScheduledByCommand[Command::WR] != lastScheduledByCommandAndRank[Command::WR][rank.ID()] ? lastScheduledByCommand[Command::WR] : sc_max_time();
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRRD_R);
 
         lastCommandStart = lastScheduledByCommandAndBankGroup[Command::WRA][bankgroup.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRRD_L);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::WRA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRRD_S);
 
-        lastCommandStart = lastScheduledByCommand[Command::WRA] != lastScheduledByCommandAndRank[Command::WRA][rank.ID()] ? lastScheduledByCommand[Command::WRA] : SC_ZERO_TIME;
-        if (lastCommandStart != SC_ZERO_TIME)
+        lastCommandStart = lastScheduledByCommand[Command::WRA] != lastScheduledByCommandAndRank[Command::WRA][rank.ID()] ? lastScheduledByCommand[Command::WRA] : sc_max_time();
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRRD_R);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PDXA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXPN);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::SREFEX][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tLK);
     }
     else if (command == Command::WR || command == Command::WRA)
     {
         lastCommandStart = lastScheduledByCommandAndBank[Command::ACT][bank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRCDWR);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::RD][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRTW);
 
-        lastCommandStart = lastScheduledByCommand[Command::RD] != lastScheduledByCommandAndRank[Command::RD][rank.ID()] ? lastScheduledByCommand[Command::RD] : SC_ZERO_TIME;
-        if (lastCommandStart != SC_ZERO_TIME)
+        lastCommandStart = lastScheduledByCommand[Command::RD] != lastScheduledByCommandAndRank[Command::RD][rank.ID()] ? lastScheduledByCommand[Command::RD] : sc_max_time();
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tRDWR_R);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::RDA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRTW);
 
-        lastCommandStart = lastScheduledByCommand[Command::RDA] != lastScheduledByCommandAndRank[Command::RDA][rank.ID()] ? lastScheduledByCommand[Command::RDA] : SC_ZERO_TIME;
-        if (lastCommandStart != SC_ZERO_TIME)
+        lastCommandStart = lastScheduledByCommand[Command::RDA] != lastScheduledByCommandAndRank[Command::RDA][rank.ID()] ? lastScheduledByCommand[Command::RDA] : sc_max_time();
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tRDWR_R);
 
         lastCommandStart = lastScheduledByCommandAndBankGroup[Command::WR][bankgroup.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tCCDL);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::WR][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tCCDS);
 
-        lastCommandStart = lastScheduledByCommand[Command::WR] != lastScheduledByCommandAndRank[Command::WR][rank.ID()] ? lastScheduledByCommand[Command::WR] : SC_ZERO_TIME;
-        if (lastCommandStart != SC_ZERO_TIME)
+        lastCommandStart = lastScheduledByCommand[Command::WR] != lastScheduledByCommandAndRank[Command::WR][rank.ID()] ? lastScheduledByCommand[Command::WR] : sc_max_time();
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tBURST + memSpec->tRTRS);
 
         lastCommandStart = lastScheduledByCommandAndBankGroup[Command::WRA][bankgroup.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tCCDL);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::WRA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tCCDS);
 
-        lastCommandStart = lastScheduledByCommand[Command::WRA] != lastScheduledByCommandAndRank[Command::WRA][rank.ID()] ? lastScheduledByCommand[Command::WRA] : SC_ZERO_TIME;
-        if (lastCommandStart != SC_ZERO_TIME)
+        lastCommandStart = lastScheduledByCommand[Command::WRA] != lastScheduledByCommandAndRank[Command::WRA][rank.ID()] ? lastScheduledByCommand[Command::WRA] : sc_max_time();
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tBURST + memSpec->tRTRS);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PDXA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXPN);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::SREFEX][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tLK);
     }
     else if (command == Command::ACT)
     {
         lastCommandStart = lastScheduledByCommandAndBank[Command::ACT][bank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRC);
 
         lastCommandStart = lastScheduledByCommandAndBankGroup[Command::ACT][bankgroup.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRRDL);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::ACT][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRRDS);
 
         lastCommandStart = lastScheduledByCommandAndBank[Command::RDA][bank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRTP + memSpec->tRP);
 
         lastCommandStart = lastScheduledByCommandAndBank[Command::WRA][bank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRPRE + memSpec->tRP);
 
         lastCommandStart = lastScheduledByCommandAndBank[Command::PRE][bank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRP);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PREA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRP);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PDXA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXPN);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PDXP][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXPN);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::REFA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRFC);
 
         lastCommandStart = lastScheduledByCommandAndBank[Command::REFB][bank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRFCPB);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::REFB][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRREFD);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::SREFEX][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXS);
 
         if (last4Activates[rank.ID()].size() >= 4)
@@ -255,145 +255,145 @@ sc_time CheckerGDDR5::timeToSatisfyConstraints(Command command, Rank rank, BankG
     else if (command == Command::PRE)
     {
         lastCommandStart = lastScheduledByCommandAndBank[Command::ACT][bank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRAS);
 
         lastCommandStart = lastScheduledByCommandAndBank[Command::RD][bank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRTP);
 
         lastCommandStart = lastScheduledByCommandAndBank[Command::WR][bank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRPRE);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PRE][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tPPD);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PDXA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXPN);
     }
     else if (command == Command::PREA)
     {
         lastCommandStart = lastScheduledByCommandAndRank[Command::ACT][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRAS);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::RD][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRTP);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::RDA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRTP);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::WR][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRPRE);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::WRA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRPRE);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PRE][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tPPD);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PDXA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXPN);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::REFB][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRFCPB);
     }
     else if (command == Command::REFA)
     {
         lastCommandStart = lastScheduledByCommandAndRank[Command::ACT][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRC);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::RDA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRTP + memSpec->tRP);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::WRA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRPRE + memSpec->tRP);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PRE][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRP);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PREA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRP);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PDXP][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXPN);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::REFA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRFC);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::REFB][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRFCPB);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::SREFEX][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXS);
     }
     else if (command == Command::REFB)
     {
         lastCommandStart = lastScheduledByCommandAndBank[Command::ACT][bank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRC);
 
         lastCommandStart = lastScheduledByCommandAndBankGroup[Command::ACT][bankgroup.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRRDL);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::ACT][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRRDS);
 
         lastCommandStart = lastScheduledByCommandAndBank[Command::RDA][bank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRTP + memSpec->tRP);
 
         lastCommandStart = lastScheduledByCommandAndBank[Command::WRA][bank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRPRE + memSpec->tRP);
 
         lastCommandStart = lastScheduledByCommandAndBank[Command::PRE][bank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRP);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PREA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRP);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PDXA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXPN);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PDXP][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXPN);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::REFA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRFC);
 
         lastCommandStart = lastScheduledByCommandAndBank[Command::REFB][bank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRFCPB);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::REFB][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
         {
             if (bankwiseRefreshCounter[rank.ID()] == 0)
                 earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRFCPB);
@@ -402,7 +402,7 @@ sc_time CheckerGDDR5::timeToSatisfyConstraints(Command command, Rank rank, BankG
         }
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::SREFEX][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXS);
 
         if (last4Activates[rank.ID()].size() >= 4)
@@ -414,112 +414,113 @@ sc_time CheckerGDDR5::timeToSatisfyConstraints(Command command, Rank rank, BankG
     else if (command == Command::PDEA)
     {
         lastCommandStart = lastScheduledByCommandAndRank[Command::RD][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tRDSRE);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::RDA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tRDSRE);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::WR][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRSRE);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::WRA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRSRE);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PDXA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXPN);
     }
     else if (command == Command::PDXA)
     {
         lastCommandStart = lastScheduledByCommandAndRank[Command::PDEA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tPD);
     }
     else if (command == Command::PDEP)
     {
         lastCommandStart = lastScheduledByCommandAndRank[Command::RD][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tRDSRE);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::RDA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tRDSRE);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::WRA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRSRE);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PDXP][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXPN);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::SREFEX][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXS);
     }
     else if (command == Command::PDXP)
     {
         lastCommandStart = lastScheduledByCommandAndRank[Command::PDEP][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tPD);
     }
     else if (command == Command::SREFEN)
     {
         lastCommandStart = lastScheduledByCommandAndRank[Command::ACT][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRC);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::RD][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tRDSRE);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::RDA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + std::max(memSpec->tRTP + memSpec->tRP, tRDSRE));
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::WRA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRPRE + memSpec->tRP);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PRE][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRP);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PREA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRP);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PDXP][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXPN);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::REFA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRFC);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::REFB][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRFCPB);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::SREFEX][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXS);
     }
     else if (command == Command::SREFEX)
     {
         lastCommandStart = lastScheduledByCommandAndRank[Command::SREFEN][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tCKE);
     }
     else
         SC_REPORT_FATAL("CheckerGDDR5", "Unknown command!");
 
     // Check if command bus is free
-    earliestTimeToStart = std::max(earliestTimeToStart, lastCommandOnBus + memSpec->tCK);
+    if (lastCommandOnBus != sc_max_time())
+        earliestTimeToStart = std::max(earliestTimeToStart, lastCommandOnBus + memSpec->tCK);
 
     return earliestTimeToStart;
 }
diff --git a/DRAMSys/library/src/controller/checker/CheckerGDDR5X.cpp b/DRAMSys/library/src/controller/checker/CheckerGDDR5X.cpp
index a19c5714..bb5679a9 100644
--- a/DRAMSys/library/src/controller/checker/CheckerGDDR5X.cpp
+++ b/DRAMSys/library/src/controller/checker/CheckerGDDR5X.cpp
@@ -42,13 +42,13 @@ CheckerGDDR5X::CheckerGDDR5X()
         SC_REPORT_FATAL("CheckerGDDR5X", "Wrong MemSpec chosen");
 
     lastScheduledByCommandAndBank = std::vector<std::vector<sc_time>>
-            (numberOfCommands(), std::vector<sc_time>(memSpec->numberOfBanks));
+            (numberOfCommands(), std::vector<sc_time>(memSpec->numberOfBanks, sc_max_time()));
     lastScheduledByCommandAndBankGroup = std::vector<std::vector<sc_time>>
-            (numberOfCommands(), std::vector<sc_time>(memSpec->numberOfBankGroups));
+            (numberOfCommands(), std::vector<sc_time>(memSpec->numberOfBankGroups, sc_max_time()));
     lastScheduledByCommandAndRank = std::vector<std::vector<sc_time>>
-            (numberOfCommands(), std::vector<sc_time>(memSpec->numberOfRanks));
-    lastScheduledByCommand = std::vector<sc_time>(numberOfCommands());
-
+            (numberOfCommands(), std::vector<sc_time>(memSpec->numberOfRanks, sc_max_time()));
+    lastScheduledByCommand = std::vector<sc_time>(numberOfCommands(), sc_max_time());
+    lastCommandOnBus = sc_max_time();
     last4Activates = std::vector<std::queue<sc_time>>(memSpec->numberOfRanks);
     last32Activates = std::vector<std::queue<sc_time>>(memSpec->numberOfRanks);
 
@@ -72,178 +72,178 @@ sc_time CheckerGDDR5X::timeToSatisfyConstraints(Command command, Rank rank, Bank
     if (command == Command::RD || command == Command::RDA)
     {
         lastCommandStart = lastScheduledByCommandAndBank[Command::ACT][bank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRCDRD);
 
         lastCommandStart = lastScheduledByCommandAndBankGroup[Command::RD][bankgroup.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tCCDL);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::RD][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tCCDS);
 
-        lastCommandStart = lastScheduledByCommand[Command::RD] != lastScheduledByCommandAndRank[Command::RD][rank.ID()] ? lastScheduledByCommand[Command::RD] : SC_ZERO_TIME;
-        if (lastCommandStart != SC_ZERO_TIME)
+        lastCommandStart = lastScheduledByCommand[Command::RD] != lastScheduledByCommandAndRank[Command::RD][rank.ID()] ? lastScheduledByCommand[Command::RD] : sc_max_time();
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tBURST + memSpec->tRTRS);
 
         lastCommandStart = lastScheduledByCommandAndBankGroup[Command::RDA][bankgroup.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tCCDL);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::RDA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tCCDS);
 
-        lastCommandStart = lastScheduledByCommand[Command::RDA] != lastScheduledByCommandAndRank[Command::RDA][rank.ID()] ? lastScheduledByCommand[Command::RDA] : SC_ZERO_TIME;
-        if (lastCommandStart != SC_ZERO_TIME)
+        lastCommandStart = lastScheduledByCommand[Command::RDA] != lastScheduledByCommandAndRank[Command::RDA][rank.ID()] ? lastScheduledByCommand[Command::RDA] : sc_max_time();
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tBURST + memSpec->tRTRS);
 
         if (command == Command::RDA)
         {
             lastCommandStart = lastScheduledByCommandAndBank[Command::WR][bank.ID()];
-            if (lastCommandStart != SC_ZERO_TIME)
+            if (lastCommandStart != sc_max_time())
                 earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRPRE - memSpec->tRTP);
         }
 
         lastCommandStart = lastScheduledByCommandAndBankGroup[Command::WR][bankgroup.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRRD_L);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::WR][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRRD_S);
 
-        lastCommandStart = lastScheduledByCommand[Command::WR] != lastScheduledByCommandAndRank[Command::WR][rank.ID()] ? lastScheduledByCommand[Command::WR] : SC_ZERO_TIME;
-        if (lastCommandStart != SC_ZERO_TIME)
+        lastCommandStart = lastScheduledByCommand[Command::WR] != lastScheduledByCommandAndRank[Command::WR][rank.ID()] ? lastScheduledByCommand[Command::WR] : sc_max_time();
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRRD_R);
 
         lastCommandStart = lastScheduledByCommandAndBankGroup[Command::WRA][bankgroup.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRRD_L);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::WRA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRRD_S);
 
-        lastCommandStart = lastScheduledByCommand[Command::WRA] != lastScheduledByCommandAndRank[Command::WRA][rank.ID()] ? lastScheduledByCommand[Command::WRA] : SC_ZERO_TIME;
-        if (lastCommandStart != SC_ZERO_TIME)
+        lastCommandStart = lastScheduledByCommand[Command::WRA] != lastScheduledByCommandAndRank[Command::WRA][rank.ID()] ? lastScheduledByCommand[Command::WRA] : sc_max_time();
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRRD_R);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PDXA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXP);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::SREFEX][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tLK);
     }
     else if (command == Command::WR || command == Command::WRA)
     {
         lastCommandStart = lastScheduledByCommandAndBank[Command::ACT][bank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRCDWR);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::RD][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRTW);
 
-        lastCommandStart = lastScheduledByCommand[Command::RD] != lastScheduledByCommandAndRank[Command::RD][rank.ID()] ? lastScheduledByCommand[Command::RD] : SC_ZERO_TIME;
-        if (lastCommandStart != SC_ZERO_TIME)
+        lastCommandStart = lastScheduledByCommand[Command::RD] != lastScheduledByCommandAndRank[Command::RD][rank.ID()] ? lastScheduledByCommand[Command::RD] : sc_max_time();
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tRDWR_R);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::RDA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRTW);
 
-        lastCommandStart = lastScheduledByCommand[Command::RDA] != lastScheduledByCommandAndRank[Command::RDA][rank.ID()] ? lastScheduledByCommand[Command::RDA] : SC_ZERO_TIME;
-        if (lastCommandStart != SC_ZERO_TIME)
+        lastCommandStart = lastScheduledByCommand[Command::RDA] != lastScheduledByCommandAndRank[Command::RDA][rank.ID()] ? lastScheduledByCommand[Command::RDA] : sc_max_time();
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tRDWR_R);
 
         lastCommandStart = lastScheduledByCommandAndBankGroup[Command::WR][bankgroup.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tCCDL);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::WR][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tCCDS);
 
-        lastCommandStart = lastScheduledByCommand[Command::WR] != lastScheduledByCommandAndRank[Command::WR][rank.ID()] ? lastScheduledByCommand[Command::WR] : SC_ZERO_TIME;
-        if (lastCommandStart != SC_ZERO_TIME)
+        lastCommandStart = lastScheduledByCommand[Command::WR] != lastScheduledByCommandAndRank[Command::WR][rank.ID()] ? lastScheduledByCommand[Command::WR] : sc_max_time();
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tBURST + memSpec->tRTRS);
 
         lastCommandStart = lastScheduledByCommandAndBankGroup[Command::WRA][bankgroup.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tCCDL);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::WRA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tCCDS);
 
-        lastCommandStart = lastScheduledByCommand[Command::WRA] != lastScheduledByCommandAndRank[Command::WRA][rank.ID()] ? lastScheduledByCommand[Command::WRA] : SC_ZERO_TIME;
-        if (lastCommandStart != SC_ZERO_TIME)
+        lastCommandStart = lastScheduledByCommand[Command::WRA] != lastScheduledByCommandAndRank[Command::WRA][rank.ID()] ? lastScheduledByCommand[Command::WRA] : sc_max_time();
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tBURST + memSpec->tRTRS);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PDXA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXP);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::SREFEX][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tLK);
     }
     else if (command == Command::ACT)
     {
         lastCommandStart = lastScheduledByCommandAndBank[Command::ACT][bank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRC);
 
         lastCommandStart = lastScheduledByCommandAndBankGroup[Command::ACT][bankgroup.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRRDL);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::ACT][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRRDS);
 
         lastCommandStart = lastScheduledByCommandAndBank[Command::RDA][bank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRTP + memSpec->tRP);
 
         lastCommandStart = lastScheduledByCommandAndBank[Command::WRA][bank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRPRE + memSpec->tRP);
 
         lastCommandStart = lastScheduledByCommandAndBank[Command::PRE][bank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRP);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PREA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRP);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PDXA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXP);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PDXP][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXP);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::REFA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRFC);
 
         lastCommandStart = lastScheduledByCommandAndBank[Command::REFB][bank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRFCPB);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::REFB][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRREFD);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::SREFEX][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXS);
 
         if (last4Activates[rank.ID()].size() >= 4)
@@ -255,145 +255,145 @@ sc_time CheckerGDDR5X::timeToSatisfyConstraints(Command command, Rank rank, Bank
     else if (command == Command::PRE)
     {
         lastCommandStart = lastScheduledByCommandAndBank[Command::ACT][bank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRAS);
 
         lastCommandStart = lastScheduledByCommandAndBank[Command::RD][bank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRTP);
 
         lastCommandStart = lastScheduledByCommandAndBank[Command::WR][bank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRPRE);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PRE][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tPPD);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PDXA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXP);
     }
     else if (command == Command::PREA)
     {
         lastCommandStart = lastScheduledByCommandAndRank[Command::ACT][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRAS);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::RD][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRTP);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::RDA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRTP);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::WR][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRPRE);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::WRA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRPRE);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PRE][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tPPD);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PDXA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXP);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::REFB][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRFCPB);
     }
     else if (command == Command::REFA)
     {
         lastCommandStart = lastScheduledByCommandAndRank[Command::ACT][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRC);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::RDA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRTP + memSpec->tRP);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::WRA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRPRE + memSpec->tRP);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PRE][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRP);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PREA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRP);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PDXP][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXP);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::REFA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRFC);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::REFB][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRFCPB);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::SREFEX][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXS);
     }
     else if (command == Command::REFB)
     {
         lastCommandStart = lastScheduledByCommandAndBank[Command::ACT][bank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRC);
 
         lastCommandStart = lastScheduledByCommandAndBankGroup[Command::ACT][bankgroup.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRRDL);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::ACT][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRRDS);
 
         lastCommandStart = lastScheduledByCommandAndBank[Command::RDA][bank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRTP + memSpec->tRP);
 
         lastCommandStart = lastScheduledByCommandAndBank[Command::WRA][bank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRPRE + memSpec->tRP);
 
         lastCommandStart = lastScheduledByCommandAndBank[Command::PRE][bank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRP);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PREA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRP);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PDXA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXP);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PDXP][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXP);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::REFA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRFC);
 
         lastCommandStart = lastScheduledByCommandAndBank[Command::REFB][bank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRFCPB);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::REFB][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
         {
             if (bankwiseRefreshCounter[rank.ID()] == 0)
                 earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRFCPB);
@@ -402,7 +402,7 @@ sc_time CheckerGDDR5X::timeToSatisfyConstraints(Command command, Rank rank, Bank
         }
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::SREFEX][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXS);
 
         if (last4Activates[rank.ID()].size() >= 4)
@@ -414,112 +414,113 @@ sc_time CheckerGDDR5X::timeToSatisfyConstraints(Command command, Rank rank, Bank
     else if (command == Command::PDEA)
     {
         lastCommandStart = lastScheduledByCommandAndRank[Command::RD][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tRDSRE);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::RDA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tRDSRE);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::WR][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRSRE);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::WRA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRSRE);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PDXA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXP);
     }
     else if (command == Command::PDXA)
     {
         lastCommandStart = lastScheduledByCommandAndRank[Command::PDEA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tPD);
     }
     else if (command == Command::PDEP)
     {
         lastCommandStart = lastScheduledByCommandAndRank[Command::RD][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tRDSRE);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::RDA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tRDSRE);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::WRA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRSRE);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PDXP][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXP);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::SREFEX][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXS);
     }
     else if (command == Command::PDXP)
     {
         lastCommandStart = lastScheduledByCommandAndRank[Command::PDEP][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tPD);
     }
     else if (command == Command::SREFEN)
     {
         lastCommandStart = lastScheduledByCommandAndRank[Command::ACT][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRC);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::RD][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tRDSRE);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::RDA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + std::max(memSpec->tRTP + memSpec->tRP, tRDSRE));
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::WRA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRPRE + memSpec->tRP);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PRE][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRP);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PREA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRP);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PDXP][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXP);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::REFA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRFC);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::REFB][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRFCPB);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::SREFEX][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXS);
     }
     else if (command == Command::SREFEX)
     {
         lastCommandStart = lastScheduledByCommandAndRank[Command::SREFEN][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tCKE);
     }
     else
         SC_REPORT_FATAL("CheckerGDDR5X", "Unknown command!");
 
     // Check if command bus is free
-    earliestTimeToStart = std::max(earliestTimeToStart, lastCommandOnBus + memSpec->tCK);
+    if (lastCommandOnBus != sc_max_time())
+        earliestTimeToStart = std::max(earliestTimeToStart, lastCommandOnBus + memSpec->tCK);
 
     return earliestTimeToStart;
 }
diff --git a/DRAMSys/library/src/controller/checker/CheckerGDDR6.cpp b/DRAMSys/library/src/controller/checker/CheckerGDDR6.cpp
index a2de6ce6..f0f6fa54 100644
--- a/DRAMSys/library/src/controller/checker/CheckerGDDR6.cpp
+++ b/DRAMSys/library/src/controller/checker/CheckerGDDR6.cpp
@@ -42,13 +42,13 @@ CheckerGDDR6::CheckerGDDR6()
         SC_REPORT_FATAL("CheckerGDDR6", "Wrong MemSpec chosen");
 
     lastScheduledByCommandAndBank = std::vector<std::vector<sc_time>>
-            (numberOfCommands(), std::vector<sc_time>(memSpec->numberOfBanks));
+            (numberOfCommands(), std::vector<sc_time>(memSpec->numberOfBanks, sc_max_time()));
     lastScheduledByCommandAndBankGroup = std::vector<std::vector<sc_time>>
-            (numberOfCommands(), std::vector<sc_time>(memSpec->numberOfBankGroups));
+            (numberOfCommands(), std::vector<sc_time>(memSpec->numberOfBankGroups, sc_max_time()));
     lastScheduledByCommandAndRank = std::vector<std::vector<sc_time>>
-            (numberOfCommands(), std::vector<sc_time>(memSpec->numberOfRanks));
-    lastScheduledByCommand = std::vector<sc_time>(numberOfCommands());
-
+            (numberOfCommands(), std::vector<sc_time>(memSpec->numberOfRanks, sc_max_time()));
+    lastScheduledByCommand = std::vector<sc_time>(numberOfCommands(), sc_max_time());
+    lastCommandOnBus = sc_max_time();
     last4Activates = std::vector<std::queue<sc_time>>(memSpec->numberOfRanks);
 
     bankwiseRefreshCounter = std::vector<unsigned>(memSpec->numberOfRanks);
@@ -71,178 +71,178 @@ sc_time CheckerGDDR6::timeToSatisfyConstraints(Command command, Rank rank, BankG
     if (command == Command::RD || command == Command::RDA)
     {
         lastCommandStart = lastScheduledByCommandAndBank[Command::ACT][bank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRCDRD);
 
         lastCommandStart = lastScheduledByCommandAndBankGroup[Command::RD][bankgroup.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tCCDL);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::RD][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tCCDS);
 
-        lastCommandStart = lastScheduledByCommand[Command::RD] != lastScheduledByCommandAndRank[Command::RD][rank.ID()] ? lastScheduledByCommand[Command::RD] : SC_ZERO_TIME;
-        if (lastCommandStart != SC_ZERO_TIME)
+        lastCommandStart = lastScheduledByCommand[Command::RD] != lastScheduledByCommandAndRank[Command::RD][rank.ID()] ? lastScheduledByCommand[Command::RD] : sc_max_time();
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tBURST + memSpec->tRTRS);
 
         lastCommandStart = lastScheduledByCommandAndBankGroup[Command::RDA][bankgroup.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tCCDL);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::RDA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tCCDS);
 
-        lastCommandStart = lastScheduledByCommand[Command::RDA] != lastScheduledByCommandAndRank[Command::RDA][rank.ID()] ? lastScheduledByCommand[Command::RDA] : SC_ZERO_TIME;
-        if (lastCommandStart != SC_ZERO_TIME)
+        lastCommandStart = lastScheduledByCommand[Command::RDA] != lastScheduledByCommandAndRank[Command::RDA][rank.ID()] ? lastScheduledByCommand[Command::RDA] : sc_max_time();
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tBURST + memSpec->tRTRS);
 
         if (command == Command::RDA)
         {
             lastCommandStart = lastScheduledByCommandAndBank[Command::WR][bank.ID()];
-            if (lastCommandStart != SC_ZERO_TIME)
+            if (lastCommandStart != sc_max_time())
                 earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRPRE - memSpec->tRTP);
         }
 
         lastCommandStart = lastScheduledByCommandAndBankGroup[Command::WR][bankgroup.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRRD_L);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::WR][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRRD_S);
 
-        lastCommandStart = lastScheduledByCommand[Command::WR] != lastScheduledByCommandAndRank[Command::WR][rank.ID()] ? lastScheduledByCommand[Command::WR] : SC_ZERO_TIME;
-        if (lastCommandStart != SC_ZERO_TIME)
+        lastCommandStart = lastScheduledByCommand[Command::WR] != lastScheduledByCommandAndRank[Command::WR][rank.ID()] ? lastScheduledByCommand[Command::WR] : sc_max_time();
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRRD_R);
 
         lastCommandStart = lastScheduledByCommandAndBankGroup[Command::WRA][bankgroup.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRRD_L);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::WRA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRRD_S);
 
-        lastCommandStart = lastScheduledByCommand[Command::WRA] != lastScheduledByCommandAndRank[Command::WRA][rank.ID()] ? lastScheduledByCommand[Command::WRA] : SC_ZERO_TIME;
-        if (lastCommandStart != SC_ZERO_TIME)
+        lastCommandStart = lastScheduledByCommand[Command::WRA] != lastScheduledByCommandAndRank[Command::WRA][rank.ID()] ? lastScheduledByCommand[Command::WRA] : sc_max_time();
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRRD_R);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PDXA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXP);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::SREFEX][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tLK);
     }
     else if (command == Command::WR || command == Command::WRA)
     {
         lastCommandStart = lastScheduledByCommandAndBank[Command::ACT][bank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRCDWR);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::RD][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRTW);
 
-        lastCommandStart = lastScheduledByCommand[Command::RD] != lastScheduledByCommandAndRank[Command::RD][rank.ID()] ? lastScheduledByCommand[Command::RD] : SC_ZERO_TIME;
-        if (lastCommandStart != SC_ZERO_TIME)
+        lastCommandStart = lastScheduledByCommand[Command::RD] != lastScheduledByCommandAndRank[Command::RD][rank.ID()] ? lastScheduledByCommand[Command::RD] : sc_max_time();
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tRDWR_R);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::RDA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRTW);
 
-        lastCommandStart = lastScheduledByCommand[Command::RDA] != lastScheduledByCommandAndRank[Command::RDA][rank.ID()] ? lastScheduledByCommand[Command::RDA] : SC_ZERO_TIME;
-        if (lastCommandStart != SC_ZERO_TIME)
+        lastCommandStart = lastScheduledByCommand[Command::RDA] != lastScheduledByCommandAndRank[Command::RDA][rank.ID()] ? lastScheduledByCommand[Command::RDA] : sc_max_time();
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tRDWR_R);
 
         lastCommandStart = lastScheduledByCommandAndBankGroup[Command::WR][bankgroup.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tCCDL);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::WR][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tCCDS);
 
-        lastCommandStart = lastScheduledByCommand[Command::WR] != lastScheduledByCommandAndRank[Command::WR][rank.ID()] ? lastScheduledByCommand[Command::WR] : SC_ZERO_TIME;
-        if (lastCommandStart != SC_ZERO_TIME)
+        lastCommandStart = lastScheduledByCommand[Command::WR] != lastScheduledByCommandAndRank[Command::WR][rank.ID()] ? lastScheduledByCommand[Command::WR] : sc_max_time();
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tBURST + memSpec->tRTRS);
 
         lastCommandStart = lastScheduledByCommandAndBankGroup[Command::WRA][bankgroup.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tCCDL);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::WRA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tCCDS);
 
-        lastCommandStart = lastScheduledByCommand[Command::WRA] != lastScheduledByCommandAndRank[Command::WRA][rank.ID()] ? lastScheduledByCommand[Command::WRA] : SC_ZERO_TIME;
-        if (lastCommandStart != SC_ZERO_TIME)
+        lastCommandStart = lastScheduledByCommand[Command::WRA] != lastScheduledByCommandAndRank[Command::WRA][rank.ID()] ? lastScheduledByCommand[Command::WRA] : sc_max_time();
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tBURST + memSpec->tRTRS);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PDXA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXP);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::SREFEX][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tLK);
     }
     else if (command == Command::ACT)
     {
         lastCommandStart = lastScheduledByCommandAndBank[Command::ACT][bank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRC);
 
         lastCommandStart = lastScheduledByCommandAndBankGroup[Command::ACT][bankgroup.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRRDL);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::ACT][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRRDS);
 
         lastCommandStart = lastScheduledByCommandAndBank[Command::RDA][bank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRTP + memSpec->tRP);
 
         lastCommandStart = lastScheduledByCommandAndBank[Command::WRA][bank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRPRE + memSpec->tRP);
 
         lastCommandStart = lastScheduledByCommandAndBank[Command::PRE][bank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRP);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PREA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRP);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PDXA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXP);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PDXP][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXP);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::REFA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRFC);
 
         lastCommandStart = lastScheduledByCommandAndBank[Command::REFB][bank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRFCPB);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::REFB][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRREFD);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::SREFEX][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXS);
 
         if (last4Activates[rank.ID()].size() >= 4)
@@ -251,145 +251,145 @@ sc_time CheckerGDDR6::timeToSatisfyConstraints(Command command, Rank rank, BankG
     else if (command == Command::PRE)
     {
         lastCommandStart = lastScheduledByCommandAndBank[Command::ACT][bank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRAS);
 
         lastCommandStart = lastScheduledByCommandAndBank[Command::RD][bank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRTP);
 
         lastCommandStart = lastScheduledByCommandAndBank[Command::WR][bank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRPRE);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PRE][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tPPD);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PDXA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXP);
     }
     else if (command == Command::PREA)
     {
         lastCommandStart = lastScheduledByCommandAndRank[Command::ACT][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRAS);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::RD][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRTP);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::RDA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRTP);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::WR][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRPRE);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::WRA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRPRE);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PRE][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tPPD);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PDXA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXP);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::REFB][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRFCPB);
     }
     else if (command == Command::REFA)
     {
         lastCommandStart = lastScheduledByCommandAndRank[Command::ACT][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRC);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::RDA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRTP + memSpec->tRP);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::WRA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRPRE + memSpec->tRP);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PRE][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRP);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PREA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRP);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PDXP][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXP);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::REFA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRFC);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::REFB][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRFCPB);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::SREFEX][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXS);
     }
     else if (command == Command::REFB)
     {
         lastCommandStart = lastScheduledByCommandAndBank[Command::ACT][bank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRC);
 
         lastCommandStart = lastScheduledByCommandAndBankGroup[Command::ACT][bankgroup.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRRDL);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::ACT][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRRDS);
 
         lastCommandStart = lastScheduledByCommandAndBank[Command::RDA][bank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRTP + memSpec->tRP);
 
         lastCommandStart = lastScheduledByCommandAndBank[Command::WRA][bank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRPRE + memSpec->tRP);
 
         lastCommandStart = lastScheduledByCommandAndBank[Command::PRE][bank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRP);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PREA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRP);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PDXA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXP);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PDXP][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXP);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::REFA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRFC);
 
         lastCommandStart = lastScheduledByCommandAndBank[Command::REFB][bank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRFCPB);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::REFB][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
         {
             if (bankwiseRefreshCounter[rank.ID()] == 0)
                 earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRFCPB);
@@ -398,7 +398,7 @@ sc_time CheckerGDDR6::timeToSatisfyConstraints(Command command, Rank rank, BankG
         }
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::SREFEX][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXS);
 
         if (last4Activates[rank.ID()].size() >= 4)
@@ -407,140 +407,141 @@ sc_time CheckerGDDR6::timeToSatisfyConstraints(Command command, Rank rank, BankG
     else if (command == Command::PDEA)
     {
         lastCommandStart = lastScheduledByCommandAndRank[Command::ACT][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tACTPDE);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::RD][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tRDSRE);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::RDA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tRDSRE);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::WR][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRSRE);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::WRA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRSRE);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PRE][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tPREPDE);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::REFB][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tREFPDE);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PDXA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXP);
     }
     else if (command == Command::PDXA)
     {
         lastCommandStart = lastScheduledByCommandAndRank[Command::PDEA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tPD);
     }
     else if (command == Command::PDEP)
     {
         lastCommandStart = lastScheduledByCommandAndRank[Command::RD][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tRDSRE);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::RDA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tRDSRE);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::WRA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRSRE);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PRE][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tPREPDE);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PREA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tPREPDE);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::REFA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tREFPDE);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::REFB][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tREFPDE);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PDXP][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXP);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::SREFEX][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXS);
     }
     else if (command == Command::PDXP)
     {
         lastCommandStart = lastScheduledByCommandAndRank[Command::PDEP][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tPD);
     }
     else if (command == Command::SREFEN)
     {
         lastCommandStart = lastScheduledByCommandAndRank[Command::ACT][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRC);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::RD][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tRDSRE);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::RDA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + std::max(memSpec->tRTP + memSpec->tRP, tRDSRE));
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::WRA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRPRE + memSpec->tRP);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PRE][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRP);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PREA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRP);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PDXP][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXP);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::REFA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRFC);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::REFB][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRFCPB);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::SREFEX][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXS);
     }
     else if (command == Command::SREFEX)
     {
         lastCommandStart = lastScheduledByCommandAndRank[Command::SREFEN][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tCKESR);
     }
     else
         SC_REPORT_FATAL("CheckerGDDR6", "Unknown command!");
 
     // Check if command bus is free
-    earliestTimeToStart = std::max(earliestTimeToStart, lastCommandOnBus + memSpec->tCK);
+    if (lastCommandOnBus != sc_max_time())
+        earliestTimeToStart = std::max(earliestTimeToStart, lastCommandOnBus + memSpec->tCK);
 
     return earliestTimeToStart;
 }
diff --git a/DRAMSys/library/src/controller/checker/CheckerHBM2.cpp b/DRAMSys/library/src/controller/checker/CheckerHBM2.cpp
index dfb2dd38..4ed20f3f 100644
--- a/DRAMSys/library/src/controller/checker/CheckerHBM2.cpp
+++ b/DRAMSys/library/src/controller/checker/CheckerHBM2.cpp
@@ -42,14 +42,16 @@ CheckerHBM2::CheckerHBM2()
         SC_REPORT_FATAL("CheckerHBM2", "Wrong MemSpec chosen");
 
     lastScheduledByCommandAndBank = std::vector<std::vector<sc_time>>
-            (numberOfCommands(), std::vector<sc_time>(memSpec->numberOfBanks));
+            (numberOfCommands(), std::vector<sc_time>(memSpec->numberOfBanks, sc_max_time()));
     lastScheduledByCommandAndBankGroup = std::vector<std::vector<sc_time>>
-            (numberOfCommands(), std::vector<sc_time>(memSpec->numberOfBankGroups));
+            (numberOfCommands(), std::vector<sc_time>(memSpec->numberOfBankGroups, sc_max_time()));
     lastScheduledByCommandAndRank = std::vector<std::vector<sc_time>>
-            (numberOfCommands(), std::vector<sc_time>(memSpec->numberOfRanks));
-    lastScheduledByCommand = std::vector<sc_time>(numberOfCommands());
-
+            (numberOfCommands(), std::vector<sc_time>(memSpec->numberOfRanks, sc_max_time()));
+    lastScheduledByCommand = std::vector<sc_time>(numberOfCommands(), sc_max_time());
+    lastCommandOnRasBus = sc_max_time();
+    lastCommandOnCasBus = sc_max_time();
     last4Activates = std::vector<std::queue<sc_time>>(memSpec->numberOfRanks);
+
     bankwiseRefreshCounter = std::vector<unsigned>(memSpec->numberOfRanks);
 
     tBURST = memSpec->burstLength / memSpec->dataRate * memSpec->tCK;
@@ -70,50 +72,50 @@ sc_time CheckerHBM2::timeToSatisfyConstraints(Command command, Rank rank, BankGr
     if (command == Command::RD || command == Command::RDA)
     {
         lastCommandStart = lastScheduledByCommandAndBank[Command::ACT][bank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRCDRD + memSpec->tCK);
 
         lastCommandStart = lastScheduledByCommandAndBankGroup[Command::RD][bankgroup.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tCCDL);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::RD][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tCCDS);
 
         lastCommandStart = lastScheduledByCommandAndBankGroup[Command::RDA][bankgroup.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tCCDL);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::RDA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tCCDS);
 
         if (command == Command::RDA)
         {
             lastCommandStart = lastScheduledByCommandAndBank[Command::WR][bank.ID()];
-            if (lastCommandStart != SC_ZERO_TIME)
+            if (lastCommandStart != sc_max_time())
                 earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRPRE - memSpec->tRTP);
         }
 
         lastCommandStart = lastScheduledByCommandAndBankGroup[Command::WR][bankgroup.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRRDL);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::WR][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRRDS);
 
         lastCommandStart = lastScheduledByCommandAndBankGroup[Command::WRA][bankgroup.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRRDL);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::WRA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRRDS);
 
         lastCommandStart = lastScheduledByCommand[Command::PDXA];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXP);
 
         earliestTimeToStart = std::max(earliestTimeToStart, lastCommandOnCasBus + memSpec->tCK);
@@ -121,35 +123,35 @@ sc_time CheckerHBM2::timeToSatisfyConstraints(Command command, Rank rank, BankGr
     else if (command == Command::WR || command == Command::WRA)
     {
         lastCommandStart = lastScheduledByCommandAndBank[Command::ACT][bank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRCDWR + memSpec->tCK);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::RD][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRTW);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::RDA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRTW);
 
         lastCommandStart = lastScheduledByCommandAndBankGroup[Command::WR][bankgroup.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tCCDL);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::WR][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tCCDS);
 
         lastCommandStart = lastScheduledByCommandAndBankGroup[Command::WRA][bankgroup.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tCCDL);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::WRA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tCCDS);
 
         lastCommandStart = lastScheduledByCommand[Command::PDXA];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXP);
 
         earliestTimeToStart = std::max(earliestTimeToStart, lastCommandOnCasBus + memSpec->tCK);
@@ -157,55 +159,55 @@ sc_time CheckerHBM2::timeToSatisfyConstraints(Command command, Rank rank, BankGr
     else if (command == Command::ACT)
     {
         lastCommandStart = lastScheduledByCommandAndBank[Command::ACT][bank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRC);
 
         lastCommandStart = lastScheduledByCommandAndBankGroup[Command::ACT][bankgroup.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRRDL);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::ACT][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRRDS);
 
         lastCommandStart = lastScheduledByCommandAndBank[Command::RDA][bank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRTP + memSpec->tRP - memSpec->tCK);
 
         lastCommandStart = lastScheduledByCommandAndBank[Command::WRA][bank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRPRE + memSpec->tRP - memSpec->tCK);
 
         lastCommandStart = lastScheduledByCommandAndBank[Command::PRE][bank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRP - memSpec->tCK);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PREA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRP - memSpec->tCK);
 
         lastCommandStart = lastScheduledByCommand[Command::PDXA];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXP - memSpec->tCK);
 
         lastCommandStart = lastScheduledByCommand[Command::PDXP];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXP - memSpec->tCK);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::REFA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRFC - memSpec->tCK);
 
         lastCommandStart = lastScheduledByCommandAndBank[Command::REFB][bank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRFCSB - memSpec->tCK);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::REFB][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRREFD - memSpec->tCK);
 
         lastCommandStart = lastScheduledByCommand[Command::SREFEX];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXS - memSpec->tCK);
 
         if (last4Activates[rank.ID()].size() >= 4)
@@ -216,19 +218,19 @@ sc_time CheckerHBM2::timeToSatisfyConstraints(Command command, Rank rank, BankGr
     else if (command == Command::PRE)
     {
         lastCommandStart = lastScheduledByCommandAndBank[Command::ACT][bank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRAS + memSpec->tCK);
 
         lastCommandStart = lastScheduledByCommandAndBank[Command::RD][bank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRTP);
 
         lastCommandStart = lastScheduledByCommandAndBank[Command::WR][bank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRPRE);
 
         lastCommandStart = lastScheduledByCommand[Command::PDXA];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXP);
 
         earliestTimeToStart = std::max(earliestTimeToStart, lastCommandOnRasBus + memSpec->tCK);
@@ -236,31 +238,31 @@ sc_time CheckerHBM2::timeToSatisfyConstraints(Command command, Rank rank, BankGr
     else if (command == Command::PREA)
     {
         lastCommandStart = lastScheduledByCommandAndRank[Command::ACT][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRAS + memSpec->tCK);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::RD][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRTP);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::RDA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRTP);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::WR][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRPRE);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::WRA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRPRE);
 
         lastCommandStart = lastScheduledByCommand[Command::PDXA];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXP);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::REFB][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRFCSB);
 
         earliestTimeToStart = std::max(earliestTimeToStart, lastCommandOnRasBus + memSpec->tCK);
@@ -268,39 +270,39 @@ sc_time CheckerHBM2::timeToSatisfyConstraints(Command command, Rank rank, BankGr
     else if (command == Command::REFA)
     {
         lastCommandStart = lastScheduledByCommandAndRank[Command::ACT][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRC + memSpec->tCK);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::RDA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRTP + memSpec->tRP);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::WRA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRPRE + memSpec->tRP);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PRE][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRP);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PREA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRP);
 
         lastCommandStart = lastScheduledByCommand[Command::PDXP];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXP);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::REFA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRFC);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::REFB][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRFCSB);
 
         lastCommandStart = lastScheduledByCommand[Command::SREFEX];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXS);
 
         earliestTimeToStart = std::max(earliestTimeToStart, lastCommandOnRasBus + memSpec->tCK);
@@ -308,51 +310,51 @@ sc_time CheckerHBM2::timeToSatisfyConstraints(Command command, Rank rank, BankGr
     else if (command == Command::REFB)
     {
         lastCommandStart = lastScheduledByCommandAndBank[Command::ACT][bank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRC + memSpec->tCK);
 
         lastCommandStart = lastScheduledByCommandAndBankGroup[Command::ACT][bankgroup.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRRDL + memSpec->tCK);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::ACT][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRRDS + memSpec->tCK);
 
         lastCommandStart = lastScheduledByCommandAndBank[Command::RDA][bank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRTP + memSpec->tRP);
 
         lastCommandStart = lastScheduledByCommandAndBank[Command::WRA][bank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRPRE + memSpec->tRP);
 
         lastCommandStart = lastScheduledByCommandAndBank[Command::PRE][bank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRP);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PREA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRP);
 
         lastCommandStart = lastScheduledByCommand[Command::PDXA];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXP);
 
         lastCommandStart = lastScheduledByCommand[Command::PDXP];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXP);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::REFA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRFC);
 
         lastCommandStart = lastScheduledByCommandAndBank[Command::REFB][bank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRFCSB);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::REFB][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
         {
             if (bankwiseRefreshCounter[rank.ID()] == 0)
                 earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRFCSB);
@@ -361,7 +363,7 @@ sc_time CheckerHBM2::timeToSatisfyConstraints(Command command, Rank rank, BankGr
         }
 
         lastCommandStart = lastScheduledByCommand[Command::SREFEX];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXS);
 
         if (last4Activates[rank.ID()].size() >= 4)
@@ -372,23 +374,23 @@ sc_time CheckerHBM2::timeToSatisfyConstraints(Command command, Rank rank, BankGr
     else if (command == Command::PDEA)
     {
         lastCommandStart = lastScheduledByCommand[Command::RD];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tRDPDE);
 
         lastCommandStart = lastScheduledByCommand[Command::RDA];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tRDPDE);
 
         lastCommandStart = lastScheduledByCommand[Command::WR];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRPDE);
 
         lastCommandStart = lastScheduledByCommand[Command::WRA];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRAPDE);
 
         lastCommandStart = lastScheduledByCommand[Command::PDXA];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tCKE);
 
         earliestTimeToStart = std::max(earliestTimeToStart, lastCommandOnRasBus + memSpec->tCK);
@@ -396,7 +398,7 @@ sc_time CheckerHBM2::timeToSatisfyConstraints(Command command, Rank rank, BankGr
     else if (command == Command::PDXA)
     {
         lastCommandStart = lastScheduledByCommand[Command::PDEA];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tPD);
 
         earliestTimeToStart = std::max(earliestTimeToStart, lastCommandOnRasBus + memSpec->tCK);
@@ -404,23 +406,23 @@ sc_time CheckerHBM2::timeToSatisfyConstraints(Command command, Rank rank, BankGr
     else if (command == Command::PDEP)
     {
         lastCommandStart = lastScheduledByCommand[Command::RD];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tRDPDE);
 
         lastCommandStart = lastScheduledByCommand[Command::RDA];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tRDPDE);
 
         lastCommandStart = lastScheduledByCommand[Command::WRA];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRAPDE);
 
         lastCommandStart = lastScheduledByCommand[Command::PDXP];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tCKE);
 
         lastCommandStart = lastScheduledByCommand[Command::SREFEX];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXS);
 
         earliestTimeToStart = std::max(earliestTimeToStart, lastCommandOnRasBus + memSpec->tCK);
@@ -428,7 +430,7 @@ sc_time CheckerHBM2::timeToSatisfyConstraints(Command command, Rank rank, BankGr
     else if (command == Command::PDXP)
     {
         lastCommandStart = lastScheduledByCommand[Command::PDEP];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tPD);
 
         earliestTimeToStart = std::max(earliestTimeToStart, lastCommandOnRasBus + memSpec->tCK);
@@ -436,39 +438,39 @@ sc_time CheckerHBM2::timeToSatisfyConstraints(Command command, Rank rank, BankGr
     else if (command == Command::SREFEN)
     {
         lastCommandStart = lastScheduledByCommand[Command::ACT];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRC + memSpec->tCK);
 
         lastCommandStart = lastScheduledByCommand[Command::RDA];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + std::max(memSpec->tRTP + memSpec->tRP, tRDSRE));
 
         lastCommandStart = lastScheduledByCommand[Command::WRA];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRPRE + memSpec->tRP);
 
         lastCommandStart = lastScheduledByCommand[Command::PRE];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRP);
 
         lastCommandStart = lastScheduledByCommand[Command::PREA];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRP);
 
         lastCommandStart = lastScheduledByCommand[Command::PDXP];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXP);
 
         lastCommandStart = lastScheduledByCommand[Command::REFA];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRFC);
 
         lastCommandStart = lastScheduledByCommand[Command::REFB];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRFCSB);
 
         lastCommandStart = lastScheduledByCommand[Command::SREFEX];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXS);
 
         earliestTimeToStart = std::max(earliestTimeToStart, lastCommandOnRasBus + memSpec->tCK);
@@ -476,7 +478,7 @@ sc_time CheckerHBM2::timeToSatisfyConstraints(Command command, Rank rank, BankGr
     else if (command == Command::SREFEX)
     {
         lastCommandStart = lastScheduledByCommand[Command::SREFEN];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tCKESR);
 
         earliestTimeToStart = std::max(earliestTimeToStart, lastCommandOnRasBus + memSpec->tCK);
@@ -484,6 +486,17 @@ sc_time CheckerHBM2::timeToSatisfyConstraints(Command command, Rank rank, BankGr
     else
         SC_REPORT_FATAL("CheckerHBM2", "Unknown command!");
 
+    if (isRasCommand(command))
+    {
+        if (lastCommandOnRasBus != sc_max_time())
+            earliestTimeToStart = std::max(earliestTimeToStart, lastCommandOnRasBus + memSpec->tCK);
+    }
+    else
+    {
+        if (lastCommandOnCasBus != sc_max_time())
+            earliestTimeToStart = std::max(earliestTimeToStart, lastCommandOnCasBus + memSpec->tCK);
+    }
+
     return earliestTimeToStart;
 }
 
diff --git a/DRAMSys/library/src/controller/checker/CheckerLPDDR4.cpp b/DRAMSys/library/src/controller/checker/CheckerLPDDR4.cpp
index e57b97d1..366f9b1f 100644
--- a/DRAMSys/library/src/controller/checker/CheckerLPDDR4.cpp
+++ b/DRAMSys/library/src/controller/checker/CheckerLPDDR4.cpp
@@ -42,11 +42,11 @@ CheckerLPDDR4::CheckerLPDDR4()
         SC_REPORT_FATAL("CheckerLPDDR4", "Wrong MemSpec chosen");
 
     lastScheduledByCommandAndBank = std::vector<std::vector<sc_time>>
-            (numberOfCommands(), std::vector<sc_time>(memSpec->numberOfBanks));
+            (numberOfCommands(), std::vector<sc_time>(memSpec->numberOfBanks, sc_max_time()));
     lastScheduledByCommandAndRank = std::vector<std::vector<sc_time>>
-            (numberOfCommands(), std::vector<sc_time>(memSpec->numberOfRanks));
-    lastScheduledByCommand = std::vector<sc_time>(numberOfCommands());
-
+            (numberOfCommands(), std::vector<sc_time>(memSpec->numberOfRanks, sc_max_time()));
+    lastScheduledByCommand = std::vector<sc_time>(numberOfCommands(), sc_max_time());
+    lastCommandOnBus = sc_max_time();
     last4Activates = std::vector<std::queue<sc_time>>(memSpec->numberOfRanks);
 
     tBURST = memSpec->burstLength / memSpec->dataRate * memSpec->tCK;
@@ -74,142 +74,142 @@ sc_time CheckerLPDDR4::timeToSatisfyConstraints(Command command, Rank rank, Bank
     if (command == Command::RD || command == Command::RDA)
     {
         lastCommandStart = lastScheduledByCommandAndBank[Command::ACT][bank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRCD);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::RD][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tCCD);
 
-        lastCommandStart = lastScheduledByCommand[Command::RD] != lastScheduledByCommandAndRank[Command::RD][rank.ID()] ? lastScheduledByCommand[Command::RD] : SC_ZERO_TIME;
-        if (lastCommandStart != SC_ZERO_TIME)
+        lastCommandStart = lastScheduledByCommand[Command::RD] != lastScheduledByCommandAndRank[Command::RD][rank.ID()] ? lastScheduledByCommand[Command::RD] : sc_max_time();
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tBURST + memSpec->tRTRS);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::RDA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tCCD);
 
-        lastCommandStart = lastScheduledByCommand[Command::RDA] != lastScheduledByCommandAndRank[Command::RDA][rank.ID()] ? lastScheduledByCommand[Command::RDA] : SC_ZERO_TIME;
-        if (lastCommandStart != SC_ZERO_TIME)
+        lastCommandStart = lastScheduledByCommand[Command::RDA] != lastScheduledByCommandAndRank[Command::RDA][rank.ID()] ? lastScheduledByCommand[Command::RDA] : sc_max_time();
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tBURST + memSpec->tRTRS);
 
         if (command == Command::RDA)
         {
             lastCommandStart = lastScheduledByCommandAndBank[Command::WR][bank.ID()];
-            if (lastCommandStart != SC_ZERO_TIME)
+            if (lastCommandStart != sc_max_time())
                 earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRPRE - tRDPRE);
         }
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::WR][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRRD);
 
-        lastCommandStart = lastScheduledByCommand[Command::WR] != lastScheduledByCommandAndRank[Command::WR][rank.ID()] ? lastScheduledByCommand[Command::WR] : SC_ZERO_TIME;
-        if (lastCommandStart != SC_ZERO_TIME)
+        lastCommandStart = lastScheduledByCommand[Command::WR] != lastScheduledByCommandAndRank[Command::WR][rank.ID()] ? lastScheduledByCommand[Command::WR] : sc_max_time();
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRRD_R);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::WRA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRRD);
 
-        lastCommandStart = lastScheduledByCommand[Command::WRA] != lastScheduledByCommandAndRank[Command::WRA][rank.ID()] ? lastScheduledByCommand[Command::WRA] : SC_ZERO_TIME;
-        if (lastCommandStart != SC_ZERO_TIME)
+        lastCommandStart = lastScheduledByCommand[Command::WRA] != lastScheduledByCommandAndRank[Command::WRA][rank.ID()] ? lastScheduledByCommand[Command::WRA] : sc_max_time();
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRRD_R);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PDXA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXP);
     }
     else if (command == Command::WR || command == Command::WRA)
     {
         lastCommandStart = lastScheduledByCommandAndBank[Command::ACT][bank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRCD);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::RD][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tRDWR);
 
-        lastCommandStart = lastScheduledByCommand[Command::RD] != lastScheduledByCommandAndRank[Command::RD][rank.ID()] ? lastScheduledByCommand[Command::RD] : SC_ZERO_TIME;
-        if (lastCommandStart != SC_ZERO_TIME)
+        lastCommandStart = lastScheduledByCommand[Command::RD] != lastScheduledByCommandAndRank[Command::RD][rank.ID()] ? lastScheduledByCommand[Command::RD] : sc_max_time();
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tRDWR_R);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::RDA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tRDWR);
 
-        lastCommandStart = lastScheduledByCommand[Command::RDA] != lastScheduledByCommandAndRank[Command::RDA][rank.ID()] ? lastScheduledByCommand[Command::RDA] : SC_ZERO_TIME;
-        if (lastCommandStart != SC_ZERO_TIME)
+        lastCommandStart = lastScheduledByCommand[Command::RDA] != lastScheduledByCommandAndRank[Command::RDA][rank.ID()] ? lastScheduledByCommand[Command::RDA] : sc_max_time();
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tRDWR_R);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::WR][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tCCD);
 
-        lastCommandStart = lastScheduledByCommand[Command::WR] != lastScheduledByCommandAndRank[Command::WR][rank.ID()] ? lastScheduledByCommand[Command::WR] : SC_ZERO_TIME;
-        if (lastCommandStart != SC_ZERO_TIME)
+        lastCommandStart = lastScheduledByCommand[Command::WR] != lastScheduledByCommandAndRank[Command::WR][rank.ID()] ? lastScheduledByCommand[Command::WR] : sc_max_time();
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tBURST + memSpec->tRTRS);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::WRA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tCCD);
 
-        lastCommandStart = lastScheduledByCommand[Command::WRA] != lastScheduledByCommandAndRank[Command::WRA][rank.ID()] ? lastScheduledByCommand[Command::WRA] : SC_ZERO_TIME;
-        if (lastCommandStart != SC_ZERO_TIME)
+        lastCommandStart = lastScheduledByCommand[Command::WRA] != lastScheduledByCommandAndRank[Command::WRA][rank.ID()] ? lastScheduledByCommand[Command::WRA] : sc_max_time();
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tBURST + memSpec->tRTRS);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PDXA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXP);
     }
     else if (command == Command::ACT)
     {
         lastCommandStart = lastScheduledByCommandAndBank[Command::ACT][bank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRCpb);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::ACT][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRRD);
 
         lastCommandStart = lastScheduledByCommandAndBank[Command::RDA][bank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tRDAACT);
 
         lastCommandStart = lastScheduledByCommandAndBank[Command::WRA][bank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRAACT);
 
         lastCommandStart = lastScheduledByCommandAndBank[Command::PRE][bank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRPpb - 2 * memSpec->tCK);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PREA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRPab - 2 * memSpec->tCK);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PDXA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXP);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PDXP][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXP);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::REFA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRFCab - 2 * memSpec->tCK);
 
         lastCommandStart = lastScheduledByCommandAndBank[Command::REFB][bank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRFCpb - 2 * memSpec->tCK);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::REFB][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRRD - 2 * memSpec->tCK);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::SREFEX][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXSR - 2 * memSpec->tCK);
 
         if (last4Activates[rank.ID()].size() >= 4)
@@ -218,141 +218,141 @@ sc_time CheckerLPDDR4::timeToSatisfyConstraints(Command command, Rank rank, Bank
     else if (command == Command::PRE)
     {
         lastCommandStart = lastScheduledByCommandAndBank[Command::ACT][bank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRAS + 2 * memSpec->tCK);
 
         lastCommandStart = lastScheduledByCommandAndBank[Command::RD][bank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tRDPRE);
 
         lastCommandStart = lastScheduledByCommandAndBank[Command::WR][bank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRPRE);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PRE][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tPPD);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PDXA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXP);
     }
     else if (command == Command::PREA)
     {
         lastCommandStart = lastScheduledByCommandAndRank[Command::ACT][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRAS + 2 * memSpec->tCK);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::RD][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tRDPRE);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::RDA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tRDPRE);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::WR][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRPRE);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::WRA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRPRE);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PRE][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tPPD);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PDXA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXP);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::REFB][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRFCpb);
     }
     else if (command == Command::REFA)
     {
         lastCommandStart = lastScheduledByCommandAndRank[Command::ACT][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRCpb + 2 * memSpec->tCK);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::RDA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tRDPRE + memSpec->tRPpb);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::WRA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRPRE + memSpec->tRPpb);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PRE][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRPpb);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PREA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRPab);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PDXP][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXP);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::REFA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRFCab);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::REFB][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRFCpb);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::SREFEX][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXSR);
     }
     else if (command == Command::REFB)
     {
         lastCommandStart = lastScheduledByCommandAndBank[Command::ACT][bank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRCpb + 2 * memSpec->tCK);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::ACT][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRRD + 2 * memSpec->tCK);
 
         lastCommandStart = lastScheduledByCommandAndBank[Command::RDA][bank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tRDPRE + memSpec->tRPpb);
 
         lastCommandStart = lastScheduledByCommandAndBank[Command::WRA][bank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRPRE + memSpec->tRPpb);
 
         lastCommandStart = lastScheduledByCommandAndBank[Command::PRE][bank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRPpb);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PREA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRPab);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PDXA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXP);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PDXP][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXP);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::REFA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRFCab);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::REFB][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRFCpb);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::SREFEX][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXSR);
 
         if (last4Activates[rank.ID()].size() >= 4)
@@ -361,136 +361,137 @@ sc_time CheckerLPDDR4::timeToSatisfyConstraints(Command command, Rank rank, Bank
     else if (command == Command::PDEA)
     {
         lastCommandStart = lastScheduledByCommandAndRank[Command::ACT][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tACTPDEN);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::RD][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tRDPDEN);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::RDA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tRDPDEN);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::WR][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRPDEN);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::WRA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRAPDEN);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PRE][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tPRPDEN);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::REFB][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tREFPDEN);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PDXA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tCKE);
     }
     else if (command == Command::PDXA)
     {
         lastCommandStart = lastScheduledByCommandAndRank[Command::PDEA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tCKE);
     }
     else if (command == Command::PDEP)
     {
         lastCommandStart = lastScheduledByCommandAndRank[Command::RD][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tRDPDEN);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::RDA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tRDPDEN);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::WRA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRAPDEN);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PRE][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tPRPDEN);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PREA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tPRPDEN);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::REFA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tREFPDEN);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::REFB][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tREFPDEN);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PDXP][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tCKE);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::SREFEX][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXSR);
     }
     else if (command == Command::PDXP)
     {
         lastCommandStart = lastScheduledByCommandAndRank[Command::PDEP][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tCKE);
     }
     else if (command == Command::SREFEN)
     {
         lastCommandStart = lastScheduledByCommandAndRank[Command::ACT][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRCpb + 2 * memSpec->tCK);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::RDA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + std::max(tRDPDEN, tRDPRE + memSpec->tRPpb));
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::WRA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + std::max(tWRAPDEN, tWRPRE + memSpec->tRPpb));
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PRE][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRPpb);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PREA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRPab);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PDXP][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXP);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::REFA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRFCab);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::REFB][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRFCpb);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::SREFEX][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXSR);
     }
     else if (command == Command::SREFEX)
     {
         lastCommandStart = lastScheduledByCommandAndRank[Command::SREFEN][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tSR);
     }
     else
         SC_REPORT_FATAL("CheckerLPDDR4", "Unknown command!");
 
     // Check if command bus is free
-    earliestTimeToStart = std::max(earliestTimeToStart, lastCommandOnBus + memSpec->tCK);
+    if (lastCommandOnBus != sc_max_time())
+        earliestTimeToStart = std::max(earliestTimeToStart, lastCommandOnBus + memSpec->tCK);
 
     return earliestTimeToStart;
 }
diff --git a/DRAMSys/library/src/controller/checker/CheckerWideIO.cpp b/DRAMSys/library/src/controller/checker/CheckerWideIO.cpp
index 946f7aff..6f588494 100644
--- a/DRAMSys/library/src/controller/checker/CheckerWideIO.cpp
+++ b/DRAMSys/library/src/controller/checker/CheckerWideIO.cpp
@@ -42,11 +42,11 @@ CheckerWideIO::CheckerWideIO()
         SC_REPORT_FATAL("CheckerWideIO", "Wrong MemSpec chosen");
 
     lastScheduledByCommandAndBank = std::vector<std::vector<sc_time>>
-            (numberOfCommands(), std::vector<sc_time>(memSpec->numberOfBanks));
+            (numberOfCommands(), std::vector<sc_time>(memSpec->numberOfBanks, sc_max_time()));
     lastScheduledByCommandAndRank = std::vector<std::vector<sc_time>>
-            (numberOfCommands(), std::vector<sc_time>(memSpec->numberOfRanks));
-    lastScheduledByCommand = std::vector<sc_time>(numberOfCommands());
-
+            (numberOfCommands(), std::vector<sc_time>(memSpec->numberOfRanks, sc_max_time()));
+    lastScheduledByCommand = std::vector<sc_time>(numberOfCommands(), sc_max_time());
+    lastCommandOnBus = sc_max_time();
     last2Activates = std::vector<std::queue<sc_time>>(memSpec->numberOfRanks);
 
     tBURST = memSpec->burstLength * memSpec->tCK;
@@ -68,134 +68,134 @@ sc_time CheckerWideIO::timeToSatisfyConstraints(Command command, Rank rank, Bank
     if (command == Command::RD || command == Command::RDA)
     {
         lastCommandStart = lastScheduledByCommandAndBank[Command::ACT][bank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRCD);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::RD][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tBURST);
 
-        lastCommandStart = lastScheduledByCommand[Command::RD] != lastScheduledByCommandAndRank[Command::RD][rank.ID()] ? lastScheduledByCommand[Command::RD] : SC_ZERO_TIME;
-        if (lastCommandStart != SC_ZERO_TIME)
+        lastCommandStart = lastScheduledByCommand[Command::RD] != lastScheduledByCommandAndRank[Command::RD][rank.ID()] ? lastScheduledByCommand[Command::RD] : sc_max_time();
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tBURST + memSpec->tRTRS);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::RDA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tBURST);
 
-        lastCommandStart = lastScheduledByCommand[Command::RDA] != lastScheduledByCommandAndRank[Command::RDA][rank.ID()] ? lastScheduledByCommand[Command::RDA] : SC_ZERO_TIME;
-        if (lastCommandStart != SC_ZERO_TIME)
+        lastCommandStart = lastScheduledByCommand[Command::RDA] != lastScheduledByCommandAndRank[Command::RDA][rank.ID()] ? lastScheduledByCommand[Command::RDA] : sc_max_time();
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tBURST + memSpec->tRTRS);
 
         if (command == Command::RDA)
         {
             lastCommandStart = lastScheduledByCommandAndBank[Command::WR][bank.ID()];
-            if (lastCommandStart != SC_ZERO_TIME)
+            if (lastCommandStart != sc_max_time())
                 earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRPRE - tBURST);
         }
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::WR][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRRD);
 
-        lastCommandStart = lastScheduledByCommand[Command::WR] != lastScheduledByCommandAndRank[Command::WR][rank.ID()] ? lastScheduledByCommand[Command::WR] : SC_ZERO_TIME;
-        if (lastCommandStart != SC_ZERO_TIME)
+        lastCommandStart = lastScheduledByCommand[Command::WR] != lastScheduledByCommandAndRank[Command::WR][rank.ID()] ? lastScheduledByCommand[Command::WR] : sc_max_time();
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRRD_R);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::WRA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRRD);
 
-        lastCommandStart = lastScheduledByCommand[Command::WRA] != lastScheduledByCommandAndRank[Command::WRA][rank.ID()] ? lastScheduledByCommand[Command::WRA] : SC_ZERO_TIME;
-        if (lastCommandStart != SC_ZERO_TIME)
+        lastCommandStart = lastScheduledByCommand[Command::WRA] != lastScheduledByCommandAndRank[Command::WRA][rank.ID()] ? lastScheduledByCommand[Command::WRA] : sc_max_time();
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRRD_R);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PDXA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXP);
     }
     else if (command == Command::WR || command == Command::WRA)
     {
         lastCommandStart = lastScheduledByCommandAndBank[Command::ACT][bank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRCD);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::RD][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tRDWR);
 
-        lastCommandStart = lastScheduledByCommand[Command::RD] != lastScheduledByCommandAndRank[Command::RD][rank.ID()] ? lastScheduledByCommand[Command::RD] : SC_ZERO_TIME;
-        if (lastCommandStart != SC_ZERO_TIME)
+        lastCommandStart = lastScheduledByCommand[Command::RD] != lastScheduledByCommandAndRank[Command::RD][rank.ID()] ? lastScheduledByCommand[Command::RD] : sc_max_time();
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tRDWR_R);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::RDA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tRDWR);
 
-        lastCommandStart = lastScheduledByCommand[Command::RDA] != lastScheduledByCommandAndRank[Command::RDA][rank.ID()] ? lastScheduledByCommand[Command::RDA] : SC_ZERO_TIME;
-        if (lastCommandStart != SC_ZERO_TIME)
+        lastCommandStart = lastScheduledByCommand[Command::RDA] != lastScheduledByCommandAndRank[Command::RDA][rank.ID()] ? lastScheduledByCommand[Command::RDA] : sc_max_time();
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tRDWR_R);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::WR][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tBURST);
 
-        lastCommandStart = lastScheduledByCommand[Command::WR] != lastScheduledByCommandAndRank[Command::WR][rank.ID()] ? lastScheduledByCommand[Command::WR] : SC_ZERO_TIME;
-        if (lastCommandStart != SC_ZERO_TIME)
+        lastCommandStart = lastScheduledByCommand[Command::WR] != lastScheduledByCommandAndRank[Command::WR][rank.ID()] ? lastScheduledByCommand[Command::WR] : sc_max_time();
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tBURST + memSpec->tRTRS);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::WRA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tBURST);
 
-        lastCommandStart = lastScheduledByCommand[Command::WRA] != lastScheduledByCommandAndRank[Command::WRA][rank.ID()] ? lastScheduledByCommand[Command::WRA] : SC_ZERO_TIME;
-        if (lastCommandStart != SC_ZERO_TIME)
+        lastCommandStart = lastScheduledByCommand[Command::WRA] != lastScheduledByCommandAndRank[Command::WRA][rank.ID()] ? lastScheduledByCommand[Command::WRA] : sc_max_time();
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tBURST + memSpec->tRTRS);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PDXA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXP);
     }
     else if (command == Command::ACT)
     {
         lastCommandStart = lastScheduledByCommandAndBank[Command::ACT][bank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRC);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::ACT][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRRD);
 
         lastCommandStart = lastScheduledByCommandAndBank[Command::RDA][bank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tBURST + memSpec->tRP);
 
         lastCommandStart = lastScheduledByCommandAndBank[Command::WRA][bank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRPRE + memSpec->tRP);
 
         lastCommandStart = lastScheduledByCommandAndBank[Command::PRE][bank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRP);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PREA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRP);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::REFA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRFC);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PDXA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXP);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PDXP][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXP);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::SREFEX][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXSR);
 
         if (last2Activates[rank.ID()].size() >= 2)
@@ -204,182 +204,183 @@ sc_time CheckerWideIO::timeToSatisfyConstraints(Command command, Rank rank, Bank
     else if (command == Command::PRE)
     {
         lastCommandStart = lastScheduledByCommandAndBank[Command::ACT][bank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRAS);
 
         lastCommandStart = lastScheduledByCommandAndBank[Command::RD][bank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tBURST);
 
         lastCommandStart = lastScheduledByCommandAndBank[Command::WR][bank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRPRE);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PDXA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXP);
     }
     else if (command == Command::PREA)
     {
         lastCommandStart = lastScheduledByCommandAndRank[Command::ACT][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRAS);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::RD][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tBURST);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::RDA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tBURST);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::WR][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRPRE);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::WRA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRPRE);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PDXA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXP);
     }
     else if (command == Command::REFA)
     {
         lastCommandStart = lastScheduledByCommandAndRank[Command::ACT][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRC);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::RDA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tBURST + memSpec->tRP);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::WRA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRPRE + memSpec->tRP);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PRE][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRP);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PREA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRP);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::REFA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRFC);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PDXP][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXP);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::SREFEX][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXSR);
     }
     else if (command == Command::PDEA)
     {
         lastCommandStart = lastScheduledByCommandAndRank[Command::RD][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tRDPDEN);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::RDA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tRDPDEN);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::WR][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRPDEN);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::WRA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRAPDEN);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PDXA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tCKE);
     }
     else if (command == Command::PDXA)
     {
         lastCommandStart = lastScheduledByCommandAndRank[Command::PDEA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tCKE);
     }
     else if (command == Command::PDEP)
     {
         lastCommandStart = lastScheduledByCommandAndRank[Command::RD][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tRDPDEN);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::RDA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tRDPDEN);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::WRA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRAPDEN);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PDXP][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tCKE);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::SREFEX][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXSR);
     }
     else if (command == Command::PDXP)
     {
         lastCommandStart = lastScheduledByCommandAndRank[Command::PDEP][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tCKE);
     }
     else if (command == Command::SREFEN)
     {
         lastCommandStart = lastScheduledByCommandAndRank[Command::ACT][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRC);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::RDA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + std::max(tRDPDEN, tBURST + memSpec->tRP));
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::WRA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + std::max(tWRAPDEN, tWRPRE + memSpec->tRP));
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PRE][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRP);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PREA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRP);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PDXP][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXP);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::REFA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRFC);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::SREFEX][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXSR);
     }
     else if (command == Command::SREFEX)
     {
         lastCommandStart = lastScheduledByCommandAndRank[Command::SREFEN][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tCKESR);
     }
     else
         SC_REPORT_FATAL("CheckerWideIO", "Unknown command!");
 
     // Check if command bus is free
-    earliestTimeToStart = std::max(earliestTimeToStart, lastScheduled + memSpec->tCK);
+    if (lastCommandOnBus != sc_max_time())
+        earliestTimeToStart = std::max(earliestTimeToStart, lastCommandOnBus + memSpec->tCK);
 
     return earliestTimeToStart;
 }
@@ -392,7 +393,7 @@ void CheckerWideIO::insert(Command command, Rank rank, BankGroup, Bank bank)
     lastScheduledByCommandAndBank[command][bank.ID()] = sc_time_stamp();
     lastScheduledByCommandAndRank[command][rank.ID()] = sc_time_stamp();
     lastScheduledByCommand[command] = sc_time_stamp();
-    lastScheduled = sc_time_stamp();
+    lastCommandOnBus = sc_time_stamp();
 
     if (command == Command::ACT)
     {
diff --git a/DRAMSys/library/src/controller/checker/CheckerWideIO.h b/DRAMSys/library/src/controller/checker/CheckerWideIO.h
index af307205..e5cdb430 100644
--- a/DRAMSys/library/src/controller/checker/CheckerWideIO.h
+++ b/DRAMSys/library/src/controller/checker/CheckerWideIO.h
@@ -54,7 +54,7 @@ private:
     std::vector<std::vector<sc_time>> lastScheduledByCommandAndBank;
     std::vector<std::vector<sc_time>> lastScheduledByCommandAndRank;
     std::vector<sc_time> lastScheduledByCommand;
-    sc_time lastScheduled;
+    sc_time lastCommandOnBus;
 
     // Four activate window
     std::vector<std::queue<sc_time>> last2Activates;
diff --git a/DRAMSys/library/src/controller/checker/CheckerWideIO2.cpp b/DRAMSys/library/src/controller/checker/CheckerWideIO2.cpp
index b21bb0b2..14818bed 100644
--- a/DRAMSys/library/src/controller/checker/CheckerWideIO2.cpp
+++ b/DRAMSys/library/src/controller/checker/CheckerWideIO2.cpp
@@ -42,11 +42,11 @@ CheckerWideIO2::CheckerWideIO2()
         SC_REPORT_FATAL("CheckerWideIO2", "Wrong MemSpec chosen");
 
     lastScheduledByCommandAndBank = std::vector<std::vector<sc_time>>
-            (numberOfCommands(), std::vector<sc_time>(memSpec->numberOfBanks));
+            (numberOfCommands(), std::vector<sc_time>(memSpec->numberOfBanks, sc_max_time()));
     lastScheduledByCommandAndRank = std::vector<std::vector<sc_time>>
-            (numberOfCommands(), std::vector<sc_time>(memSpec->numberOfRanks));
-    lastScheduledByCommand = std::vector<sc_time>(numberOfCommands());
-
+            (numberOfCommands(), std::vector<sc_time>(memSpec->numberOfRanks, sc_max_time()));
+    lastScheduledByCommand = std::vector<sc_time>(numberOfCommands(), sc_max_time());
+    lastCommandOnBus = sc_max_time();
     last4Activates = std::vector<std::queue<sc_time>>(memSpec->numberOfRanks);
 
     tBURST = memSpec->burstLength / memSpec->dataRate * memSpec->tCK;
@@ -69,142 +69,142 @@ sc_time CheckerWideIO2::timeToSatisfyConstraints(Command command, Rank rank, Ban
     if (command == Command::RD || command == Command::RDA)
     {
         lastCommandStart = lastScheduledByCommandAndBank[Command::ACT][bank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRCD);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::RD][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tCCD);
 
-        lastCommandStart = lastScheduledByCommand[Command::RD] != lastScheduledByCommandAndRank[Command::RD][rank.ID()] ? lastScheduledByCommand[Command::RD] : SC_ZERO_TIME;
-        if (lastCommandStart != SC_ZERO_TIME)
+        lastCommandStart = lastScheduledByCommand[Command::RD] != lastScheduledByCommandAndRank[Command::RD][rank.ID()] ? lastScheduledByCommand[Command::RD] : sc_max_time();
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tBURST + memSpec->tRTRS);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::RDA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tCCD);
 
-        lastCommandStart = lastScheduledByCommand[Command::RDA] != lastScheduledByCommandAndRank[Command::RDA][rank.ID()] ? lastScheduledByCommand[Command::RDA] : SC_ZERO_TIME;
-        if (lastCommandStart != SC_ZERO_TIME)
+        lastCommandStart = lastScheduledByCommand[Command::RDA] != lastScheduledByCommandAndRank[Command::RDA][rank.ID()] ? lastScheduledByCommand[Command::RDA] : sc_max_time();
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tBURST + memSpec->tRTRS);
 
         if (command == Command::RDA)
         {
             lastCommandStart = lastScheduledByCommandAndBank[Command::WR][bank.ID()];
-            if (lastCommandStart != SC_ZERO_TIME)
+            if (lastCommandStart != sc_max_time())
                 earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRPRE - tRDPRE);
         }
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::WR][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRRD);
 
-        lastCommandStart = lastScheduledByCommand[Command::WR] != lastScheduledByCommandAndRank[Command::WR][rank.ID()] ? lastScheduledByCommand[Command::WR] : SC_ZERO_TIME;
-        if (lastCommandStart != SC_ZERO_TIME)
+        lastCommandStart = lastScheduledByCommand[Command::WR] != lastScheduledByCommandAndRank[Command::WR][rank.ID()] ? lastScheduledByCommand[Command::WR] : sc_max_time();
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRRD_R);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::WRA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRRD);
 
-        lastCommandStart = lastScheduledByCommand[Command::WRA] != lastScheduledByCommandAndRank[Command::WRA][rank.ID()] ? lastScheduledByCommand[Command::WRA] : SC_ZERO_TIME;
-        if (lastCommandStart != SC_ZERO_TIME)
+        lastCommandStart = lastScheduledByCommand[Command::WRA] != lastScheduledByCommandAndRank[Command::WRA][rank.ID()] ? lastScheduledByCommand[Command::WRA] : sc_max_time();
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRRD_R);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PDXA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXP);
     }
     else if (command == Command::WR || command == Command::WRA)
     {
         lastCommandStart = lastScheduledByCommandAndBank[Command::ACT][bank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRCD);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::RD][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tRDWR);
 
-        lastCommandStart = lastScheduledByCommand[Command::RD] != lastScheduledByCommandAndRank[Command::RD][rank.ID()] ? lastScheduledByCommand[Command::RD] : SC_ZERO_TIME;
-        if (lastCommandStart != SC_ZERO_TIME)
+        lastCommandStart = lastScheduledByCommand[Command::RD] != lastScheduledByCommandAndRank[Command::RD][rank.ID()] ? lastScheduledByCommand[Command::RD] : sc_max_time();
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tRDWR_R);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::RDA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tRDWR);
 
-        lastCommandStart = lastScheduledByCommand[Command::RDA] != lastScheduledByCommandAndRank[Command::RDA][rank.ID()] ? lastScheduledByCommand[Command::RDA] : SC_ZERO_TIME;
-        if (lastCommandStart != SC_ZERO_TIME)
+        lastCommandStart = lastScheduledByCommand[Command::RDA] != lastScheduledByCommandAndRank[Command::RDA][rank.ID()] ? lastScheduledByCommand[Command::RDA] : sc_max_time();
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tRDWR_R);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::WR][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tCCD);
 
-        lastCommandStart = lastScheduledByCommand[Command::WR] != lastScheduledByCommandAndRank[Command::WR][rank.ID()] ? lastScheduledByCommand[Command::WR] : SC_ZERO_TIME;
-        if (lastCommandStart != SC_ZERO_TIME)
+        lastCommandStart = lastScheduledByCommand[Command::WR] != lastScheduledByCommandAndRank[Command::WR][rank.ID()] ? lastScheduledByCommand[Command::WR] : sc_max_time();
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tBURST + memSpec->tRTRS);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::WRA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tCCD);
 
-        lastCommandStart = lastScheduledByCommand[Command::WRA] != lastScheduledByCommandAndRank[Command::WRA][rank.ID()] ? lastScheduledByCommand[Command::WRA] : SC_ZERO_TIME;
-        if (lastCommandStart != SC_ZERO_TIME)
+        lastCommandStart = lastScheduledByCommand[Command::WRA] != lastScheduledByCommandAndRank[Command::WRA][rank.ID()] ? lastScheduledByCommand[Command::WRA] : sc_max_time();
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tBURST + memSpec->tRTRS);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PDXA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXP);
     }
     else if (command == Command::ACT)
     {
         lastCommandStart = lastScheduledByCommandAndBank[Command::ACT][bank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRCpb);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::ACT][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRRD);
 
         lastCommandStart = lastScheduledByCommandAndBank[Command::RDA][bank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tRDPRE + memSpec->tRPpb);
 
         lastCommandStart = lastScheduledByCommandAndBank[Command::WRA][bank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRPRE + memSpec->tRPpb);
 
         lastCommandStart = lastScheduledByCommandAndBank[Command::PRE][bank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRPpb);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PREA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRPab);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PDXA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXP);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PDXP][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXP);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::REFA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRFCab);
 
         lastCommandStart = lastScheduledByCommandAndBank[Command::REFB][bank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRFCpb);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::REFB][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRRD);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::SREFEX][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXSR);
 
         if (last4Activates[rank.ID()].size() >= 4)
@@ -213,141 +213,141 @@ sc_time CheckerWideIO2::timeToSatisfyConstraints(Command command, Rank rank, Ban
     else if (command == Command::PRE)
     {
         lastCommandStart = lastScheduledByCommandAndBank[Command::ACT][bank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRAS);
 
         lastCommandStart = lastScheduledByCommandAndBank[Command::RD][bank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tRDPRE);
 
         lastCommandStart = lastScheduledByCommandAndBank[Command::WR][bank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRPRE);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PRE][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + 2 * memSpec->tCK);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PDXA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXP);
     }
     else if (command == Command::PREA)
     {
         lastCommandStart = lastScheduledByCommandAndRank[Command::ACT][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRAS);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::RD][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tRDPRE);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::RDA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tRDPRE);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::WR][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRPRE);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::WRA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRPRE);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PRE][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + 2 * memSpec->tCK);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PDXA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXP);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::REFB][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRFCpb);
     }
     else if(command == Command::REFA)
     {
         lastCommandStart = lastScheduledByCommandAndRank[Command::ACT][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRCpb);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::RDA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tRDPRE + memSpec->tRPpb);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::WRA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRPRE + memSpec->tRPpb);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PRE][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRPpb);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PREA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRPab);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PDXP][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXP);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::REFA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRFCab);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::REFB][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRFCpb);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::SREFEX][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXSR);
     }
     else if(command == Command::REFB)
     {
         lastCommandStart = lastScheduledByCommandAndBank[Command::ACT][bank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRCpb);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::ACT][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRRD);
 
         lastCommandStart = lastScheduledByCommandAndBank[Command::RDA][bank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tRDPRE + memSpec->tRPpb);
 
         lastCommandStart = lastScheduledByCommandAndBank[Command::WRA][bank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRPRE + memSpec->tRPpb);
 
         lastCommandStart = lastScheduledByCommandAndBank[Command::PRE][bank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRPpb);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PREA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRPab);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PDXA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXP);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PDXP][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXP);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::REFA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRFCab);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::REFB][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRFCpb);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::SREFEX][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXSR);
 
         if (last4Activates[rank.ID()].size() >= 4)
@@ -356,108 +356,109 @@ sc_time CheckerWideIO2::timeToSatisfyConstraints(Command command, Rank rank, Ban
     else if (command == Command::PDEA)
     {
         lastCommandStart = lastScheduledByCommandAndRank[Command::RD][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tRDPDEN);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::RDA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tRDPDEN);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::WR][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRPDEN);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::WRA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRAPDEN);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PDXA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tCKE);
     }
     else if (command == Command::PDXA)
     {
         lastCommandStart = lastScheduledByCommandAndRank[Command::PDEA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tCKE);
     }
     else if (command == Command::PDEP)
     {
         lastCommandStart = lastScheduledByCommandAndRank[Command::RD][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tRDPDEN);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::RDA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tRDPDEN);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::WRA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + tWRAPDEN);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PDXP][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tCKE);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::SREFEX][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXSR);
     }
     else if (command == Command::PDXP)
     {
         lastCommandStart = lastScheduledByCommandAndRank[Command::PDEP][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tCKE);
     }
     else if (command == Command::SREFEN)
     {
         lastCommandStart = lastScheduledByCommandAndRank[Command::ACT][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRCpb);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::RDA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + std::max(tRDPDEN, tRDPRE + memSpec->tRPpb));
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::WRA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + std::max(tWRAPDEN, tWRPRE + memSpec->tRPpb));
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PRE][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRPpb);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PREA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRPab);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::PDXP][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXP);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::REFA][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRFCab);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::REFB][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tRFCpb);
 
         lastCommandStart = lastScheduledByCommandAndRank[Command::SREFEX][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tXSR);
     }
     else if (command == Command::SREFEX)
     {
         lastCommandStart = lastScheduledByCommandAndRank[Command::SREFEN][rank.ID()];
-        if (lastCommandStart != SC_ZERO_TIME)
+        if (lastCommandStart != sc_max_time())
             earliestTimeToStart = std::max(earliestTimeToStart, lastCommandStart + memSpec->tCKESR);
     }
     else
         SC_REPORT_FATAL("CheckerWideIO2", "Unknown command!");
 
     // Check if command bus is free
-    earliestTimeToStart = std::max(earliestTimeToStart, lastCommandOnBus + memSpec->tCK);
+    if (lastCommandOnBus != sc_max_time())
+        earliestTimeToStart = std::max(earliestTimeToStart, lastCommandOnBus + memSpec->tCK);
 
     return earliestTimeToStart;
 }