The Accellera version reports an error if the period, high or low portions of the clock are zero. Change-Id: I2cbb7c3a1b6abe4d969ef875ebf8754d2d1c489a Reviewed-on: https://gem5-review.googlesource.com/c/13303 Reviewed-by: Gabe Black <gabeblack@google.com> Maintainer: Gabe Black <gabeblack@google.com>