For OFFSETs with both positive and negative edge flip-flops, TRCE incorrectly calculates slack for negative-edge flip-flops. This causes problems with the correlation of Trace and PrimeTime simulations.
TRACE calculates offset slacks for two-phase clocks by basing the calculation on the respective edges. PrimeTime, on the other hand, bases its slack calculation on only the rising clock edge for both positive- and negative-edge flops.
To remedy this issue, create a group and OFFSET it for the positive set of flip-flops; create another group and OFFSET it for the negative-edge flip-flops.
This issue will be fixed in the next major software release.