Update: my enthusiasm was misplaced because I was fooled by CPU usage. It turns out that the CPU usage I was seeing was mostly overhead busy work (thread contention), not useful computation.
CPU utilization is not the same as useful work accomplished. See the real story.
In the next few weeks I’ll be doing an all-new investigation of the use of CPU cores in Photoshop in particular, because things have changed (not sure when exactly), and much for the better.
Today I was researching how well CPU cores are used in the latest Adobe Photoshop CC and I’m pleased to report that some old rules can now be forgotten: I am seeing that 12 cores handily outperform 8 cores or 6 cores even on common tasks like Smart Sharpen.
I’ve pre-tested my current 12-core 3.33 GHz 2010 Mac Pro by disabling CPU cores from scheduling, in order to directly compare on the same machine. Those CPU cores all run at their full speed of 3.33 GHz, so the actual behavior remains to be seen on the 2013 Mac Pro, where use of more CPU cores ramps down the clock speed for all of them.
Choose the best number of CPU cores for your actual work: