I was a wee bit early with my “Murphy’s Law” prediction (it took 5 weeks instead of 2), but the 8 core Mac Pro is now available at the Apple Store .
If you are considering the Mac Pro 8 core option, be sure to read my March 13 blog entry discussing memory bandwidth—the 8 core Mac Pro is hampered by memory bandwidth (the rate at which memory can be read or written). Apple’s marketing claim of 21GB/sec memory bandwidth should be considered the drivel that it is—testing doesn’t support the claim, showing a maximum memory copy speed of 2.9GB / sec. As that includes reads and writes, we can conclude that for a real program, memory bandwidth is about 5.8GB/sec, and that’s if it’s not competing with any other cores for access to memory.
Ironically, any job that can actually make use of 8 cores (rare) will be hampered by the reduced memory bandwidth available. So in terms of real world performance, think of 8 cores as 6 cores when compared to the quad core Mac Pro—a step up worth paying for highly specialized tasks, but not for most users—I’ve yet to see all 4 cores of my quad-core Mac Pro at full utilization (except using diglloydTools, an artificial case).