OWC 16GB Memory Modules Performance on 3.33Ghz 12-Core Mac Pro (2011 variant)
The January, 2012 dual-rank modules run at 1333MHz, and can be expected to perform slightly better than what is shown here.
All memory modules used were OWC memory. The results shown here are with Mac OS X 10.6.7 and the latest Photoshop CS5 12.0.4 64-bit.
Memory clock speed and hence memory bandwidth is one measure of performance, but in the real world with real programs, the on-chip caches often hide memory bandwidth limitations; this varies by task because of the amount and pattern of memory access during computation.
Note: as previously documented, Photoshop CS5 is faster on a 6-core Mac Pro than on a 12-core Mac Pro, this is not new and has nothing to do with the memory, but rather with engineering assumptions that degrade performance.
Get 16GB modules here.
Photoshop CS5 12.0.4 diglloydSpeed1 benchmark
Using 6 modules is optimal for memory bandwidth; 8 modules is just a tiny bit slower in this test, consistent with past results.
Not shown is 4 X 16GB which is off the chart: 155 seconds, because the system sees 64GB as 2GB, and thrashes wildly with massive virtual memory page swapping.
Photoshop CS5 12.0.4 diglloydMedium benchmark
Using 6 modules is optimal for memory bandwidth; 8 modules is just a bit slower in this test, consistent with past results.
Not shown is 4 X 16GB which is off the chart: 362 seconds, because the system sees 64GB as 2GB, and thrashes wildly with massive virtual memory page swapping.
Photoshop CS5 12.0.4 diglloydHuge benchmark
The speed of this test is driven entirely by whether there is enough memory: note that even 64GB is not quite enough.
Lightroom 3.3 Import 128 CR2 RAW files
Import 128 CR2 RAW files, generating 1:1 high-quality previews.
Lightroom 3.3 is not demanding of the amount of memory while importing, and the bandwidth apparently has little effect on the 12-core Mac Pro, most likely because LR3 does a poor job of using all the CPU cores, so the memory bandwidth needs are relatively low, since no more than about half the cores are actually used.
The MemoryTester compute test is moderately memory intensive, and thus sensitive to memory bandwidth.
Six modules is optimal, with a clear loss of performance using eight modules. The Mac Pro uses triple channel memory (two channels of 3 modules each), so with eight modules it must drop down to dual-channel bandwidth.
Note: more than 96GB is not recognized and used.