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Up Topic Rybka Support & Discussion / Aquarium / SMT / Hyperthreading
- - By BHGP (**) Date 2019-05-07 05:40

what is the actual meaning about SMT / Hyperthreading and AMD Ryzen with chess-software and/or other software? Better not  to use? Advantages / Disadvantages?
Do I have it to switch off in BIOS permanently?
Parent - By pawnslinger (****) Date 2019-05-07 17:21 Edited 2019-05-07 17:40
This is a very complicated topic.  And no very clear direction is available.  For many years, it was generally thought that Hyper-threading (HT) as Intel calls it, or  Symmetrical Multi-threading (SMT) as AMD calls it, was counter-productive.  Yet many people have used it with great success, including myself.

The original HT from Intel was very inefficient, but I used it anyway.  When I switched to Ryzen processors, I began to use SMT, as a matter of course.  The first thing that I noticed was that the AMD version in Ryzen chips seemed more efficient than what I had been using with Intel... but this could be due to the fact that I was using an old Intel chip, perhaps their newer offerings are more efficient.

In any case, engines under multi-threading are not as fast as they are without it.  How big a hit do you take by using multi-threading?  That is hard to judge accurately.  Probably anywhere from 20-30 percent.  But I have found, in my own work, that Chess analysis overall benefits from more cores, even if they are slower cores.  And most modern operating systems generally have many many threads active, so they too benefit from more cores being available... up to a point.  And I am afraid that that is completely subjective, differing from one processor to another and from one operating system to another... not all handle multi-processing with the same efficiency.
Up Topic Rybka Support & Discussion / Aquarium / SMT / Hyperthreading

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