the name of this "feature" is appalling [LWN.net]

the name of this "feature" is appalling

Posted Feb 18, 2022 20:50 UTC (Fri) by jhoblitt (subscriber, #77733)
Parent article: Thoughts on software-defined silicon

If there is no FPGA, CPLD, or microcode involved than the name of this "feature" is badly inaccurate, even by the usual marketing standards. This is nothing more than MSRs to turn on and off features baked into the die. I am skeptical that even "enterprise", let alone "hyperscaler", customers are enthusiastic about having to deal with per socket license entitlement. AMD is going to finally start shipping avx512 support. It seems like adding avx512 to "e-cores" for a consistent desktop/server fp abi would have been a much more productive use of engineering time.

the name of this "feature" is appalling

Posted Feb 19, 2022 1:58 UTC (Sat) by flussence (guest, #85566) [Link] (4 responses)

This is the first I've heard of AMD having plans for AVX512. I thought they didn't see it going anywhere?

the name of this "feature" is appalling

Posted Feb 19, 2022 9:36 UTC (Sat) by developer122 (guest, #152928) [Link] (2 responses)

I'm surprised. Intel is killing it off with Alder (lava) Lake.

the name of this "feature" is appalling

Posted Feb 19, 2022 11:32 UTC (Sat) by pbonzini (subscriber, #60935) [Link]

It's still there on server parts, and with growing functionality.

the name of this "feature" is appalling

Posted Feb 19, 2022 13:29 UTC (Sat) by khim (subscriber, #9252) [Link]

Intel overestimated the speed of changes in the software realm. Alder Lake have some cores which support AVX512 and some that don't support it yet.

I guess the optimistic thinking was that software would adopt, somehow.

But software was barely able to adopt cores with different speed, neither Linux nor Windows is ready to deal with cores with different instructions sets!

Thus it was easier for Intel to disable it rather then try to create some buggy driver which would do something with that mess.

the name of this "feature" is appalling

Posted Feb 19, 2022 15:33 UTC (Sat) by jhoblitt (subscriber, #77733) [Link]

It has been widely reported that zen4 will finally add avx512, including leaked screen shots of an AMD manual. AFAIK there has been no public confirmation from AMD. There are probably enough engineering samples floating around at this point that we will know one way or the other soon. Avx512 complicates the decision as to whether or not to use a gpu for fp intensive code. It is a lot easier to change some compiler flags/add some code annotations than committing to debugging a cuda pipeline. Without fancy SIMD instructions, the choice of cpu is less relevant as the system will probably have one or more Nvidia gpus installed anyways.