There is 64GB of memory in my 3.33 GHz 12-core Mac Pro as 8 X 8GB modules.
Photoshop CS6 is configured to use up to ~71% of the memory, or about 44GB.
Today, that was not enough memory while I was preparing a comparison of the Nikon D800E to the Nikon D800.
Photoshop hit memory usage of 43.8GB, and this caused the system to start virtual memory paging, which shows up as progress dialogs suddenly popping up, along with sluggish response time.
But the virtual memory paging “hit” was greatly mitigated by the fact that I had dual OWC Mercury Accelsior PCIe SSD cards in a RAID-0 stripe— system paging could happen at up to 1200 MB/sec, or about 8-10 times as fast as a fast empty hard drive.
The best solution for low memory is to add memory; in my case, to upgrade from 48GB to 96GB of system memory. But that’s about $1400. The Accelsior PCIe SSD takes most of the pain away from virtual memory paging, and it’s a solution that offers many benefits, so for now I’ll save the $1400 and be happy that the Accelsior setup saved the day.