Originally posted by macrumors12345
Because the Opteron is quite similar to the Athlon but with four key advantages: better floating point performance, 64-bit instructions, better memory bandwidth, and SSE2 support. Of those four advantages, only the last two are even relevant for Photoshop, and they probably will not be enough to offset the Xeon's HT advantage.
Regarding the benchmarks you posted, I will admit that the Opteron performed better than I expected. Unfortunately, since they only give the aggregate score (of what appears to be a PSBench run, from comparing the Athlon MP 2200 times to Ace's Athlon MP 2200 times), we have no idea how the Opteron and the Xeon actually compare to each other - all we are doing is comparing four filters (accent edges, pointillaze, water color, and radial blur). For the record, I doubt that the GamePC website was being dishonest when they gave the aggregate PSBench score - they probably just do not understand that the aggregate score is not meaningful for PSBench (which is understandable since they area gaming site, not a graphic design site).
The strange thing is that the PSBench aggregate score seems to be heavily memory constrained - that is partially why the Opteron is doing much better than the Athlon and the Xeon/3.06 1 MB does much better than the Xeon/3.06. But the G5/1.6 actually has the fastest memory subsystem of all the system's in Ace's test, so why doesn't it *really* clean up? Possibly cache is more important than memory bandwidth in this test (the Xeon 1 MB and the Opteron both have big caches), or possibly some key PSBench filters have not yet been optimized for the G5. It would be very helpful if we could actually see some detailed, consistent G4 PSBench scores, but those have yet to appear.
Incidentally, I did not say I was "so sure" the Xeon would beat the Opteron. I said that I would be quite surprised if the Opteron won in Photoshop. And I will still be surprised if the Opteron wins in Photoshop. What I am SURE of is that the Opteron will not beat the Dual G5 in Photoshop. You can bet money on that. (and in case it was unclear, getting a high aggregate score in PSBench does not constitute "winning", anymore than winning in an Apple run benchmark at WWDC constitutes "winning" - at a very minimum you need to win a clear majority of the subtests).