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Re: Komodo 11.3

Posted: Sun Mar 04, 2018 8:52 pm
by mjlef
Just a reminder that some newer AMD processors run the BMI2 PEXT instruction slower than normal. So pn these machine, just use the regular 64 bit version instead of the BMI2 version. I am not sure why the PEXT instruction is so slow on some of these chips. It would be nice if a microcode update told fix that, but I am guessing they are emulate PEXT in software.

Re: Komodo 11.3

Posted: Mon Mar 05, 2018 12:40 pm
by Werewolf
Mark,

Am I right in saying the BMI2 build will benefit Haswell onwards?

I thought we once had a conversation together where you thought Skylake had removed the instructions to take advantage of this. Is that correct?

If so, is the situation the same with Kaby Lake and Coffee Lake etc?

Thanks, Carl

Re: Komodo 11.3

Posted: Tue Mar 06, 2018 12:48 am
by mjlef
Werewolf wrote:Mark,

Am I right in saying the BMI2 build will benefit Haswell onwards?

I thought we once had a conversation together where you thought Skylake had removed the instructions to take advantage of this. Is that correct?

If so, is the situation the same with Kaby Lake and Coffee Lake etc?

Thanks, Carl
So these support BMI2:

"Intel Haswell processors and newer (like Skylake, Broadwell)"

I cannot predict what Intel might do in the future, but so far Intel has continued support in these lines.

I have a small program to test some CPU bit to see what is supported. I might put that on our website so people can run it on their machines to see what is supported. But basically, if the BMI2 compile does not work, use the other 64 bit version. For AMD, use the non-BMI2 version. At least until they speed up the BMI2 instructions.

Re: Komodo 11.3

Posted: Tue Mar 06, 2018 1:59 am
by tpoppins
mjlef wrote:So these support BMI2:

"Intel Haswell processors and newer (like Skylake, Broadwell)"

I cannot predict what Intel might do in the future, but so far Intel has continued support in these lines.
Although BMI2 instructions give only up to 5% speedup in some applications itt would make zero sense business-wise for Intel to remove them from their new processors unless it were to replace them with something considerably better (which is not likely to happen for a long while yet).
mjlef wrote:I have a small program to test some CPU bit to see what is supported. I might put that on our website so people can run it on their machines to see what is supported.
Or you could simply post a link to CPU-Z which is the most common tool for this purpose on Windoze and not have to provide support for yet another program. :)