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Old 12th April 2018, 17:57   #6017  |  Link
Asmodian
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Join Date: Feb 2002
Location: San Jose, California
Posts: 4,406
Quote:
Originally Posted by nevcairiel View Post
Asmodian runs without a AVX512 offset, which would instantly crash his system if a strong AVX512 workload would run, so clearly its faster with some "light" AVX512 usage. Usually you need at least a -10 offset or such to get it working stable under strong AVX512 load (or boost voltages substantially for more heat). Non-OCed Xeon CPUs probably downlock quite substantially.
I had downclocked from my normal max clocks when running without an AVX offset.

I also ran some tests at my normal OC settings with -2, -4 multiplier offsets. 4.8 GHz max core, 4.6 GHz AVX2, 4.4 GHz AVX-512.

AVX512: encoded 1000 frames in 310.46s (3.22 fps), 4037.41 kb/s, Avg QP:20.64
AVX2: encoded 1000 frames in 335.85s (2.98 fps), 4037.41 kb/s, Avg QP:20.64

It would probably still melt with a heavy AVX-512 load but it also wasn't completely maxed. AVX-512 ran cooler than AVX2 at these settings. I am not sure why my AVX2 run only had the same speed as the previous 4.5 GHz encode, maybe a latency penalty due to the core changing states.

This is a binned, delidded, and water cooled CPU... other systems may have different results.

Edit: If I run Prime95 (p95v294b8) with AVX-512 at 4.5 GHz I do get thermal throttling.
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Last edited by Asmodian; 12th April 2018 at 19:09.
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