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Up Topic The Rybka Lounge / Computer Chess / Stockfish on AMD Ryzen must use MODERN, not BMI2 !!
- - By MrKris (***) Date 2019-12-31 02:50
https://groups.google.com/forum/?nomobile=true#!topic/fishcooking/p95_pNZekg0
Stockfish 10 on AMD 3950X
3 posts by 2 authors
  branko....@gmail.com  
12:35 PM (5 hours ago)

I recently bought an AMD 3950x and was expecting to get great results when playing engine to engine matches online. But I only get about 20 to 25 ply search depth, and keep loosing games against much weaker CPUs.

My settings are as follow:

Threads:32
Ponder:on
Contempt: both, (have tried both 0 and 24)
Time settings 5min +5

CPU is liquid cooled and I am using precision boost which holds stable at around 4,2GHz

What am I missing? Why do I keep loosing against i5 CPUs?


- - - - - -

Even though Ryzen does BMI2 (FX/Phenom did not) it is some sort of emulation, very much slower than on an Intel:
http://www.ipmanchess.yolasite.com/amd---intel-chess-bench.php
101.442.355
AMD Ryzen Threadripper 3 3970X @3.9Ghz 64threads
pop Monstru  (pop = abrok modern)

82.180.052
AMD Ryzen Threadripper 3 3970X @3.9Ghz 64threads
BMI2 Monstru (presumably the same machine)
Parent - By user923005 (****) Date 2019-12-31 04:21 Upvotes 1
You are correct. The BMI instructions on Ryzen machines are very bad.  But the SSE stuff works fine
Up Topic The Rybka Lounge / Computer Chess / Stockfish on AMD Ryzen must use MODERN, not BMI2 !!

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