ACS needs lots of cpus, otherwise it's no value, because it's "distrubuted synthesis", the acs engine partition big design into small pieces, and synthesis them concurrently in many cpus, that's why it can handle large designs and improve runtime.
I have found a training manual about ACS.
It's in 1999 written by synopsys and you can download it from EDAboard.
Ali corporation use ACS 2004.06 version to synthesis a small design "PBIU".
ACS (Automated Chip Synthesis) command is used in large designs. This basically performs synthesis by partitioning the deisgn (as per our inputs). It accepts top level constraints but interprets and applies them properly for different partitions automatically. The synthesis of different partitions is launched parallely inorder to speed up the computations.