After many test positions it seems there is little difference in using UMA vs Numa, but there is a difference.
Running Lc0 using 2 threads Numa had an advantage of 3.23%
Running Stockfish using 32 threads Numa had an advantage of 5.16%
Threadripper runs by default in Uma mode.
This can be changed with the Ryzen Master Software by using local memory mode. And will continue to use what ever mode you choose after a shutdown or restart.
Threadripper optimization for chess engines Uma vs Numa
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mwyoung
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Threadripper optimization for chess engines Uma vs Numa
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M ANSARI
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Re: Threadripper optimization for chess engines Uma vs Numa
Interesting, I would have thought that anything over 4 or 6 cores favors Uma.
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jjoshua2
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Re: Threadripper optimization for chess engines Uma vs Numa
Uma has greater memory bandwidth (since it can also use memory channels that are further away) but higher memory latency. So for hash tables numa is better.