40+ threads of rendering goodness. I'm surprised at the performance degradation with hyperthreading on under Windows. Makes no sense, even under full hardware threads.
Windows Server 2008 R2? :\
I'm not quite understanding what this is testing, can anyone break it down or distill it?
Performance scaling based on number of threads and cores. That quad Xeon has a total of 40 cores and 80 hardware threads. Ideally, with 40 threads, there should be a 40x speedup in render times compared with one core. As you can see, the max is only about 24x to 29x. With HT on under Windows, it's even less.
ok and why do you think that is? and why doesnt the piledriver opteron have similar results?
They recompiled povray on linux but didn't do so on Windows. I'm not sure how much that would make a difference, but something to keep in mind.
Unlikely given that there's a table that shows that under Linux HT brings some small speedups (with 40 cores, 40s, with 40+HT, 32s), and on top of that it's ~20% faster so memory congestion would be even more of an issue.1) I don't know, but I would guess memory access congestion due to so many threads.