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On the desktop chips (x299) it's easy to adjust all the clock speeds in the bios. If the workloads I'm most interested in are all avx512-heavy (why I bought x2
by celrod 7y ago
On the desktop chips (x299) it's easy to adjust all the clock speeds in the bios.
If the workloads I'm most interested in are all avx512-heavy (why I bought x299 instead of threadripper), do you think there'd be a reason to set the clock speeds to be equal, regardless of ISA?
That is, if I currently have 4.6/4.3/4.1 GHz no-avx/avx(2)/avx512, when might it be worth setting all three of these to 4.1 GHz?
I suspect "never" is the answer?
I have the impression that Zen's clocking algorithm is much smarter than Intel's heuristic approach.
- BeeOnRope 7y agoI don't think it makes sense, because the maximum penalty due to the tranitions is fairly low (~30 us out of 650 us, and only under pretty much a malicious load that transitions at exactly the right points), and mostly you want the higher frequencies when you can get them: they quickly overwhelm the small transition periods. Also, someone indicated to me in private correspondence that even when the frequencies are manually set so no transition takes place, the throttling periods may still take place (which makes sense since the required voltage may still be higher).