The results are generally what one might expect, but with some perverse results for Photoshop CS4, which I explain in When More is Less. We’ll probably have to wait for a (hopefully) 64-bit CS5 to see this problem go away, as milking the cows seems to be the priority for now.
As shown below, a single-CPU Mac Pro handily beats a dual-CPU Mac Pro on the diglloydMedium benchmark by 45 seconds to 61 seconds. Anyone working with large file(s) that use the scratch volume should sit up and pay attention here.
I also intensively tested the OWC 4GB modules in the single-core Mac Pro and they show no issues whatsoever—rock solid, just as in my dual-core Mac Pro. At $1749 for 32GB versus $6100 from Apple, the OWC product is the right choice. Single-CPU Mac Pro Nehalem users have only 4 slots, so four 4GB modules are the only way to get to 16GB (or 12GB).