Are you kidding?

By: juanrga (nospam.delete@this.juanrga.com), October 7, 2015 10:56 am
Room: Moderated Discussions
Stubabe (Stubabe.delete@this.nospam.com) on October 7, 2015 1:17 am wrote:

> So if YOU are claiming Haswell is a 8-wide design by counting fused uops as 2 (and I think you are the
> only one here that is) then Skylake is 12wide allocate with 16 wide retire. However, these values are
> clearly unrealistic not least because Haswell cannot sustain 8-issue under any possible non-microcoded
> x86 code sequence. So a more reasonable description is Haswell is 4 wide and Skylake is 6 wide.
>

Since this thread is spinning towards another useless terminology/convention fight. I will just add this relevant quote and move on:

A processor such as Core i*4/i*5 Haswell/Broadwell, for example, can decode up to 5 x86 instructions per cycle, producing a maximum of up to 4 fused μops per cycle, which are then stored in an L0 μop cache, from which up to 4 fused μops per cycle are fetched, then register-renamed and placed into a reorder buffer, from which up to 8 un-fused individual μops are issued per cycle to the functional units, where they proceed down the various pipelines until they complete, whereupon up to 4 fused μops per cycle can be committed and retired. So what does that make the width of Haswell/Broadwell? It's really an 8-issue processor at heart, since up to 8 un-fused μops can be fetched, issued and completed per cycle if they're paired/fused in just the right way (and an un-fused μop is the most direct equivalent of a simple RISC instruction), but even experts disagree on exactly what to call the width of such a design, since 4-issue would also be valid, in terms of fused μops, which is what the processor mostly "thinks in terms of" for tracking purposes, and 5-issue is also valid if thinking in terms of original x86 instructions. Of course, this width-labelling conundrum is largely academic, since no processor is likely to actually sustain such high levels of ILP when running real-world code anyway.

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TopicPosted ByDate
Update to Intel Optimization ManualSHK2015/09/29 05:38 AM
  gather speedEric Bron2015/09/29 09:43 AM
    gather speedGabriele Svelto2015/09/29 12:00 PM
  Update to Intel Optimization ManualTim McCaffrey2015/09/29 11:18 AM
    Update to Intel Optimization ManualSHK2015/09/29 12:04 PM
      Update to Intel Optimization ManualAnon2015/09/29 02:23 PM
    Update to Intel Optimization Manualnone2015/09/29 10:31 PM
      Update to Intel Optimization ManualMichael S2015/09/30 04:24 AM
    Update to Intel Optimization ManualMichael S2015/09/30 04:30 AM
      Update to Intel Optimization ManualTim McCaffrey2015/09/30 10:01 AM
  5-6 wide core, why no mention from Intel?Wouter Tinus2015/09/30 02:14 PM
    5-6 wide core, why no mention from Intel?Maynard Handley2015/09/30 03:30 PM
      5-6 wide core, why no mention from Intel?Alberto2015/10/01 12:13 AM
        5-6 wide core, why no mention from Intel?anon2015/10/01 02:21 AM
          5-6 wide core, why no mention from Intel?Alberto2015/10/01 04:41 AM
            5-6 wide core, why no mention from Intel?anon2015/10/01 05:27 AM
              5-6 wide core, why no mention from Intel?Alberto2015/10/01 08:33 AM
                5-6 wide core, why no mention from Intel?juanrga2015/10/01 10:24 AM
        5-6 wide core, why no mention from Intel?Maynard Handley2015/10/01 08:57 AM
    5-6 wide core, why no mention from Intel?juanrga2015/10/01 03:59 AM
      5-6 wide core, why no mention from Intel?Wouter Tinus2015/10/01 02:48 PM
        5-6 wide core, why no mention from Intel?juanrga2015/10/03 03:17 AM
          5-6 wide core, why no mention from Intel?Wouter Tinus2015/10/03 11:19 AM
            Are you kidding? (NT)juanrga2015/10/04 05:30 AM
              Are you kidding?Wouter Tinus2015/10/04 03:18 PM
                Are you kidding?juanrga2015/10/05 09:46 AM
                  Are you kidding?David Kanter2015/10/05 11:24 AM
                    Are you kidding?anon2015/10/05 09:26 PM
                    Are you kidding?Linus Torvalds2015/10/07 04:49 AM
                      Are you kidding?juanrga2015/10/07 10:46 AM
                        Are you kidding?anon2015/10/07 06:21 PM
                  Are you kidding?Wouter Tinus2015/10/05 01:25 PM
                    Are you kidding?juanrga2015/10/06 10:17 AM
                      Are you kidding?Stubabe2015/10/07 12:17 AM
                        Are you kidding?juanrga2015/10/07 10:56 AM
                          Amazing...Wouter Tinus2015/10/07 11:31 AM
                            Amazing...juanrga2015/10/07 03:45 PM
                          Are you kidding?Stubabe2015/10/07 11:57 AM
                            Are you kidding?juanrga2015/10/07 03:59 PM
                          Are you kidding?Wilco2015/10/07 02:07 PM
                            Are you kidding?juanrga2015/10/07 04:33 PM
      5-6 wide core, why no mention from Intel?Eric Bron2015/10/04 04:18 AM
    5-6 wide core, why no mention from Intel?David Kanter2015/10/01 09:01 AM
      Optimal number and kind of execution unitsjuanrga2015/10/01 10:50 AM
        Optimal number and kind of execution unitsPatrick Chase2015/10/01 04:38 PM
          Optimal number and kind of execution unitsI.S.T.2015/10/01 05:10 PM
            Optimal number and kind of execution unitsPatrick Chase2015/10/01 11:39 PM
          Optimal number and kind of execution unitsExophase2015/10/01 10:11 PM
          Optimal number and kind of execution unitsjuanrga2015/10/02 05:14 AM
      LD/ST unitsSHK2015/10/01 11:11 AM
        LD/ST unitsDavid Kanter2015/10/01 12:54 PM
          LD/ST unitsSHK2015/10/02 04:55 AM
            LD/ST unitsJukka Larja2015/10/02 09:49 PM
        LD/ST unitsMaynard Handley2015/10/01 01:01 PM
          LD/ST unitsanon2015/10/01 09:54 PM
      5-6 wide core, why no mention from Intel?Maynard Handley2015/10/01 12:57 PM
        5-6 wide core, why no mention from Intel?David Kanter2015/10/01 03:49 PM
          5-6 wide core, why no mention from Intel?Maynard Handley2015/10/01 06:21 PM
          5-6 wide core, why no mention from Intel?Exophase2015/10/01 10:07 PM
            5-6 wide core, why no mention from Intel?Maynard Handley2015/10/02 12:10 AM
              5-6 wide core, why no mention from Intel?Megol2015/10/02 03:39 AM
                5-6 wide core, why no mention from Intel?Michael S2015/10/02 04:27 AM
                5-6 wide core, why no mention from Intel?Maynard Handley2015/10/02 09:37 AM
                  5-6 wide core, why no mention from Intel?noko2015/10/02 05:19 PM
              5-6 wide core, why no mention from Intel?Exophase2015/10/02 06:43 AM
                5-6 wide core, why no mention from Intel?Maynard Handley2015/10/02 09:45 AM
                  5-6 wide core, why no mention from Intel?Exophase2015/10/02 10:23 AM
          5-6 wide core, why no mention from Intel?Wilco2015/10/02 12:48 PM
            5-6 wide core, why no mention from Intel?Maynard Handley2015/10/02 01:25 PM
              5-6 wide core, why no mention from Intel?Wilco2015/10/02 02:26 PM
              5-6 wide core, why no mention from Intel?noko2015/10/02 05:45 PM
                5-6 wide core, why no mention from Intel?Maynard Handley2015/10/02 06:54 PM
            5-6 wide core, why no mention from Intel?David Kanter2015/10/02 01:59 PM
              5-6 wide core, why no mention from Intel?Wilco2015/10/02 02:59 PM
                5-6 wide core, why no mention from Intel?David Kanter2015/10/02 03:15 PM
                  5-6 wide core, why no mention from Intel?Wilco2015/10/02 04:06 PM
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                      LDP/STP usage in AArch64 for 403.gccWilco2015/10/03 03:02 AM
                        LDP/STP usage in AArch64 for 403.gccnone2015/10/03 03:11 AM
                          LDP/STP usage in AArch64 for 403.gccWilco2015/10/03 03:37 AM
                            LDP/STP usage in AArch64 for 403.gccnone2015/10/03 04:37 AM
                              LDP/STP usage in AArch64 for 403.gccWilco2015/10/03 05:26 AM
                  5-6 wide core, why no mention from Intel?Maynard Handley2015/10/02 04:24 PM
              5-6 wide core, why no mention from Intel?Maynard Handley2015/10/02 03:07 PM
  Update to Intel Optimization Manualanon2015/09/30 04:43 PM
  Update to Intel Optimization ManualPatrick Chase2015/09/30 09:44 PM
    Update to Intel Optimization Manualanon2015/09/30 10:49 PM
    Update to Intel Optimization Manualnone2015/09/30 10:50 PM
    Update to Intel Optimization ManualDavid Kanter2015/10/01 12:52 PM
      Update to Intel Optimization ManualPatrick Chase2015/10/01 04:16 PM
        Update to Intel Optimization Manualanon2015/10/01 10:45 PM
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