KNL obsolete, AVX512 - a huge mistake

By: bakaneko (nyan.delete@this.hyan.wan), August 26, 2015 6:00 am
Room: Moderated Discussions
Michael S (already5chosen.delete@this.yahoo.com) on August 26, 2015 5:13 am wrote:
> bakaneko (nyan.delete@this.hyan.wan) on August 26, 2015 5:01 am wrote:
> > Michael S (already5chosen.delete@this.yahoo.com) on August 26, 2015 4:23 am wrote:
> > > bakaneko (nyan.delete@this.hyan.wan) on August 26, 2015 3:44 am wrote:
> > > > Sure, except KNL can be improved by the time that becomes possible.
> > > >
> > > > And mentioning AVX-1024 for current hardware borders on trolling.
> > > >
> > > > All your post really boils down to is that KNL will become obsolete when its successor comes out.
> > >
> > > My post is about Intel taking a wrong (IMHO) technical path when they started to work on KNC
> > > successor. Which, according to my understanding, happened ~1 year before KNC shipment date,
> > > i.e. 3.5 years ago. If right decisions were taken back in 2012 then my imaginary chip could
> > > have been done about now, certainly not later than KNL as we know it, because the development
> > > will be somewhat simpler (fewer completely new parts, heavier reuse of existing assets) .
> > > They clearly (IMHO) underestimated the ability of their [then non-existing] 14 nm process
> > > to deliver SandyBridge-like cores that rival perf/Watt of much simpler cores.
> > >
> > > As to mentioning AVX-1024 for current hardware, that's the whole point! They should (IMHO)
> > > have skipped AVX512 completely and to jump straight from AVX256 to at least AVX1024.
> > >
> > > Personally, I'd prefer even wider registers (4096 bit sounds about right) with exactly the same ISA
> > > supported over all market segments with varying width of actual execution units. Something like 64b
> > > DP/128b SP execution units on phones/tablets, 256b DP/SP on mainstream laptop/desktop/E3s, either
> > > 128b or 256b on E5/E7, 1024b DP/SP on HPC parts, 1024b DP/2048b SP on imaging/military parts.
> > > However, if all we are looking for is an HPC competitor for Maxwell-based Teslas, then straight-forward
> > > 1024-bit registers backed byh 1024-bit execution units will do the trick.
> >
> > Except it's huge nonsense without any relation to reality and technical problems. The varying
> > width of execution units isn't the problem anyway as it is done everywhere, if it was that
> > easy Intel would have found a way to support all of 512 and 1024 bit wide AVX even with
> > tight opcode space. A student in their first year learning HDL can do that.
> >
> > Obviously didn't happen. And it becomes obvious if you think about other changes necessary for a wider SIMD.
>
> It does happen all the time.
> As a most technically sound of relatively recent examples from general-purpose
> land, Jauguar runs AVX256 through 64-bit wide DP EUs and 128b-wide SP EUs.
> Intel itself (Silvermont), runs SSE128 through 64-bit DP EUs and the actual FP multiplier
> is yet narrower than 64 bits. The did the same many yeas ago on Banias/Dothan/Yonah.
>
> 1024-bit EUs with 4096-bit registers were part of very detailed
> proposition for Alpha Tarantula from ~15 years ago.
> And, of course, there are plenty of more specialized NEC and
> Fujitsu chips doing the same, including few pretty recent.
>
>

What didn't happen was AVX-1024. Obviously splitting up SIMD ops happens all the time happens:

> The varying width of execution units isn't the problem anyway as it is done everywhere [...]
> A student in their first year learning HDL can do that.

No clue how you managed to misread that, especially because you called SIMD units execution units.
< Previous Post in ThreadNext Post in Thread >
TopicPosted ByDate
KNL obsolete, AVX512 - a huge mistakeMichael S2015/08/25 02:58 PM
  KNL obsolete, AVX512 - a huge mistakeMark Roulo2015/08/25 04:10 PM
    KNL obsolete, AVX512 - a huge mistakeMichael S2015/08/25 04:23 PM
  KNL obsolete, AVX512 - a huge mistakejuanrga2015/08/25 06:01 PM
    KNL obsolete, AVX512 - a huge mistakeAnon2015/08/26 01:23 AM
      KNL obsolete, AVX512 - a huge mistakejuanrga2015/08/26 05:49 AM
        KNL obsolete, AVX512 - a huge mistakeAlberto2015/08/26 06:26 AM
          KNL obsolete, AVX512 - a huge mistakejuanrga2015/08/26 11:23 AM
            KNL obsolete, AVX512 - a huge mistakeAlberto2015/08/26 01:13 PM
    KNL obsolete, AVX512 - a huge mistakeAaron Spink2015/08/26 07:25 AM
      KNL obsolete, AVX512 - a huge mistakejuanrga2015/08/26 12:11 PM
  Core M vs Atom- well duhAnon2015/08/26 01:19 AM
    Core M vs Atom- well duhMichael S2015/08/26 02:59 AM
      Core M vs Atom- well duhAnon2015/08/26 03:37 AM
  KNL obsolete, AVX512 - a huge mistakebakaneko2015/08/26 03:44 AM
    KNL obsolete, AVX512 - a huge mistakeMichael S2015/08/26 04:23 AM
      KNL obsolete, AVX512 - a huge mistakebakaneko2015/08/26 05:01 AM
        KNL obsolete, AVX512 - a huge mistakeMichael S2015/08/26 05:13 AM
          KNL obsolete, AVX512 - a huge mistakebakaneko2015/08/26 06:00 AM
      KNL obsolete, AVX512 - a huge mistakeNoSpammer2015/08/26 06:33 AM
        KNL obsolete, AVX512 - a huge mistakeMichael S2015/08/26 06:43 AM
  KNL obsolete, AVX512 - a huge mistakempx2015/08/31 03:15 AM
  KNL obsolete, AVX512 - a huge mistakePassing Through2018/08/03 11:02 AM
  KNL obsolete, AVX512 - a huge mistakecoppice2018/08/04 04:34 AM
    KNL obsolete, AVX512 - a huge mistakePassing Through2018/08/04 06:58 AM
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