5 ms·

I agree, but so is AVX10/256, get rid of that also thanks:)

MobiusHorizons 3y ago
why? As I understand it 256 bit avx has been standard on x86 CPUs for generations. avx10 in this context just changes the number of instructions that can be done with 256bit registers. seems like it would be pretty silly to remove 256bit avx that is already useful.
- aleph_minus_one 3y ago
  > why? As I understand it 256 bit avx has been standard on x86 CPUs for generations. The Atom-derived cores did not support AVX for quite a long time. Even the Tremont microarchitecture (i.e. Elkhart Lake launched in September 2020 and Jasper Lake launched January 2021) does not support AVX. Only from the Gracemont microarchitecture on (launched in November 2021), there exist Intel Atom processors that support AVX/AVX2.
  - Am4TIfIsER0ppos 3y ago
    AVX was also unavailable on Pentium and Celeron branded processors but I think that has changed.
    - aleph_minus_one 3y ago
      These are based on the same microarchitecture as the Atom cores, so it was also a problem up to Tremont. With the Gracemont microarchitecture, this "principally" changed, but until now Intel has not announced any processor of this microarchitecture that it branded "Pentium" or "Celeron": > https://en.wikipedia.org/w/index.php?title=Gracemont_(microarchitecture)&oldid=1170238307 https://en.wikipedia.org/w/index.php?title=Gracemont_(microa...
      - Am4TIfIsER0ppos 3y ago
        Are they? (Were they?) I assumed they were the main Core architecture just with features removed, either by design or after production.
        RaisingSpear 3y ago
        Both are true. Some Atom line processors were branded Pentium/Celeron. The low end big core SKUs were also branded Pentium/Celeron (and often had features disabled).
- TinkersW 3y ago
  You are misunderstanding, avx10/256 adds nothing, all those instructions already exist under avx512. All avx10/256 does is create yet another target, would be better to unify under avx512(which already supports 256 & 128 registers as a requirement).
  - raphlinus 3y ago
    I don't agree. A 256 bit profile of the new AVX stuff gives you lots of goodies over AVX2, including mask predication, the fancy ternary op, and so on. Additionally, because it consumes half as many register bits as the 512 bit profile, it could be a lot more economical (and power efficient) to implement on cores that are not the high end server parts. Keep in mind ARM (even the top of their line) is still stuck on 128. So I think the case for this is a good one.
    - anonymoushn 3y ago
      To clarify for readers, since I'm sure raphlinus understands this, those 256-bit instructions are present in AVX-512. But it will be nice to have those 256-bit instructions (my favorites are vpcompressb and friends) on cpus that do not have 512-bit instructions.
  - jcranmer 3y ago
    AVX10/256 allows you to use the EVEX encoding with 256-bit registers without assuming that you'll have 512-bit register support. And if I have to be honest, it's all the things that EVEX encoding adds (double the number of registers, per-instruction rounding modes, masked vector operations) that are interesting, not the fact that you have 512-bit registers.
    - TinkersW 3y ago
      Those things are nice but in the end if I'm trying to get the most work done in the shortest amount of time, having wider registers help more than that stuff.
      - 3y ago

why? As I understand it 256 bit avx has been standard on x86 CPUs for generations. avx10 in this context just changes the number of instructions that can be done with 256bit registers. seems like it would be pretty silly to remove 256bit avx that is already useful.

aleph_minus_one 3y ago
> why? As I understand it 256 bit avx has been standard on x86 CPUs for generations. The Atom-derived cores did not support AVX for quite a long time. Even the Tremont microarchitecture (i.e. Elkhart Lake launched in September 2020 and Jasper Lake launched January 2021) does not support AVX. Only from the Gracemont microarchitecture on (launched in November 2021), there exist Intel Atom processors that support AVX/AVX2.
- Am4TIfIsER0ppos 3y ago
  AVX was also unavailable on Pentium and Celeron branded processors but I think that has changed.
  - aleph_minus_one 3y ago
    These are based on the same microarchitecture as the Atom cores, so it was also a problem up to Tremont. With the Gracemont microarchitecture, this "principally" changed, but until now Intel has not announced any processor of this microarchitecture that it branded "Pentium" or "Celeron": > https://en.wikipedia.org/w/index.php?title=Gracemont_(microarchitecture)&oldid=1170238307 https://en.wikipedia.org/w/index.php?title=Gracemont_(microa...
    - Am4TIfIsER0ppos 3y ago
      Are they? (Were they?) I assumed they were the main Core architecture just with features removed, either by design or after production.
      - RaisingSpear 3y ago
        Both are true. Some Atom line processors were branded Pentium/Celeron. The low end big core SKUs were also branded Pentium/Celeron (and often had features disabled).
TinkersW 3y ago
You are misunderstanding, avx10/256 adds nothing, all those instructions already exist under avx512. All avx10/256 does is create yet another target, would be better to unify under avx512(which already supports 256 & 128 registers as a requirement).
- raphlinus 3y ago
  I don't agree. A 256 bit profile of the new AVX stuff gives you lots of goodies over AVX2, including mask predication, the fancy ternary op, and so on. Additionally, because it consumes half as many register bits as the 512 bit profile, it could be a lot more economical (and power efficient) to implement on cores that are not the high end server parts. Keep in mind ARM (even the top of their line) is still stuck on 128. So I think the case for this is a good one.
  - anonymoushn 3y ago
    To clarify for readers, since I'm sure raphlinus understands this, those 256-bit instructions are present in AVX-512. But it will be nice to have those 256-bit instructions (my favorites are vpcompressb and friends) on cpus that do not have 512-bit instructions.
- jcranmer 3y ago
  AVX10/256 allows you to use the EVEX encoding with 256-bit registers without assuming that you'll have 512-bit register support. And if I have to be honest, it's all the things that EVEX encoding adds (double the number of registers, per-instruction rounding modes, masked vector operations) that are interesting, not the fact that you have 512-bit registers.
  - TinkersW 3y ago
    Those things are nice but in the end if I'm trying to get the most work done in the shortest amount of time, having wider registers help more than that stuff.
    - 3y ago