Hi cilao,

1) yes, PAC simulation requires a PSS solution as an initial operating point.
For help try:
spectre -h pac

2) yes, its is possible to save the PSS result and use it (load it) for use with pac simualtion without the need to recompute it. For details try
spectre -h pss
And use "writepss" and "readpss".

cheers
aw

The first run will be the same as a normal run length time as you have to write the pss file. (Perhaps you have someone else of you machine using compute resource ?!?)
Subsequent runs should be much quicker if you put the writepss file name into the readpss field in the pss options form. This is because the pss part of the simulation will now only do quick re-check that the read pss solution meets the convergence requirements  (rather than recompute tstab and pss soltuion from scratch) before moving onto to the pac run.