Article: Knights Landing CPU Speculation
By: Michael S (already5chosen.delete@this.yahoo.com), November 22, 2013 4:41 am
Room: Moderated Discussions
Eric (eric.kjellen.delete@this.gmail.com) on November 22, 2013 3:10 am wrote:
> Michael S (already5chosen.delete@this.yahoo.com) on November 21, 2013 6:48 am wrote:
> > Eric (eric.kjellen.delete@this.gmail.com) on November 21, 2013 2:28 am wrote:
> > > Daniel (x.delete@this.y.z) on November 20, 2013 2:04 pm wrote:
> > > > Could they have opted for 2 vector units per core? This would make KNL more similar
> > > > to SKL from an EU point of view and might explain the decision to go for OoO FP.
> > >
> > > That thought struck me too: 2x 512-bit vector units with FMA would give 32 DP FLOP/clock
> > > and 72 cores would need 1.3 GHz to give 3 TFLOPS (3 TFLOP/s / (32 FLOP * 72) = 1.302 GHz)
> > > which would be a more incremental clock frequency boost over previous-generation MIC.
> >
> > 2 FPUs on 2-issue core? That's silly. 2-issue is barely enough to keep one FPU reasonably busy. I say,
> > barely, because, judging by Top500 list, KNC (and Kepler) delivers much lower sustained-to-peak ratio
> > than just about everybody else, and that on the benchamark that is commonly considered easy.
> >
> Yeah, that explanation might not make sense. However, it has to be explained how 72 cores (presumably
> Atom/Silvermont) with a 512-bit vector unit (for 16 DP FLOP/cycle with FMA) can achieve 3 DP TFLOPS.
> My first thought would be that the number of cores is incorrect, but Intel has previously stated
> that future Xeon Phi designs (and this was said in 2011 and should include Knights Landing) will
> be based on Atom cores.

I'd like to see a quote.

> And getting a comparable high number of cores (>100) that they would from
> a scale-up of the P54C derivative many-core design in KNC (57-61 cores) would probably not be possible
> if Atom cores are used, as one Atom core is much larger and power hungry.
> What's puzzling is also that while 2.6 GHz is way too high for a highly-parallel chip, 72 cores that compute
> 16 DP FLOP per core and cycle at this clock frequency exactly matches the 3 DP TFLOPS peak performance figure
> provided by Intel, though this so far is not exactly significant as the 2.6 GHz was something we grabbed
> out of thin air for the very purpose of solving this equation. On the other hand, assuming 32 DP FLOP pe
> core and cycle and a matching halving of the clock speed then results in a 1.3 GHz clock frequency which
> is only slightly higher than Knights Corner (proudction Xeon Phi of this generation offers clock frequencies
> in a range from 1.053 GHz to 1.238 GHz) and a very realistic increase for the die shrink from 22nm to 14nm.
> This would suggest that the 72 core figure is correct but Intel has somehow managed to make each core work
> as if it had double 512-bit vector units or a single 1024-bit vector unit (here I am reminded of Nicholas
> Capen's predictions for future AVX/LRBni convergence) so that it can process 32 DP FLOP/cycle.

1024-bit makes a lot of sense from technical perspective. Except that Intel already said, unequivocally, that Knights Landing implements AVX-512 :(
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TopicPosted ByDate
Knights Landing CPU SpeculationDavid Kanter2013/11/18 02:03 AM
  Knights Landing CPU Speculationnone2013/11/18 02:59 AM
    Knights Landing CPU SpeculationPatrick Chase2013/11/23 03:18 PM
      Knights Landing CPU SpeculationAdam Kalisz2013/11/26 01:20 AM
        Over 2,000 mm^2 of eDRAM???Mark Roulo2013/11/26 09:28 AM
          Over 2,000 mm^2 of eDRAM???David Kanter2013/11/26 11:09 AM
          Over 2,000 mm^2 of eDRAM???Eric Bron2013/11/26 11:21 AM
            Over 2,000 mm^2 of eDRAM???tarlinian2013/11/26 11:50 AM
              Over 2,000 mm^2 of eDRAM???Eric Bron2013/11/26 01:07 PM
                Over 2,000 mm^2 of eDRAM???Eric Bron2013/11/26 01:09 PM
                Over 2,000 mm^2 of eDRAM???aaron spink2013/11/26 03:03 PM
                  Over 2,000 mm^2 of eDRAM???Eric Bron2013/11/26 11:42 PM
                    Over 2,000 mm^2 of eDRAM???aaron spink2013/11/27 10:31 AM
              Over 2,000 mm^2 of eDRAM???David Kanter2013/11/26 04:25 PM
                Over 2,000 mm^2 of eDRAM???tarlinian2013/11/26 07:01 PM
          Over 2,000 mm^2 of eDRAM???Eric2013/11/27 02:54 AM
            eDRAM is DRAM in a logic-oriented processPaul A. Clayton2013/11/27 07:10 AM
  Knights Landing CPU SpeculationJames2013/11/18 05:26 AM
    Knights Landing CPU SpeculationMichael S2013/11/18 02:57 PM
      Knights Landing CPU SpeculationUrban Novak2013/11/19 12:49 AM
        Knights Landing CPU Speculationnone2013/11/19 01:19 AM
          Knights Landing CPU SpeculationEric2013/11/19 07:48 PM
            Total GPGPU/Xeon Phi market maybe ~ $500M/year ...Mark Roulo2013/11/20 10:35 AM
      Knights Landing CPU SpeculationWes Felter2013/11/19 12:06 PM
        Knights Landing CPU SpeculationMichael S2013/11/19 12:49 PM
  Knights Landing CPU SpeculationEric2013/11/18 12:17 PM
    Knights Landing CPU SpeculationDaniel2013/11/19 02:28 AM
      Knights Landing CPU SpeculationEric2013/11/19 07:36 PM
      HPC guys score FLOPS non-obviouslyMark Roulo2013/11/20 10:43 AM
        3-TFlops-DGEMMMichael S2013/11/20 10:59 AM
          3-TFlops-DGEMMMark Roulo2013/11/20 12:22 PM
            3-TFlops-DGEMMDaniel2013/11/20 01:04 PM
              3-TFlops-DGEMMEric2013/11/21 01:28 AM
                3-TFlops-DGEMMMichael S2013/11/21 05:48 AM
                  3-TFlops-DGEMMRecessionCone2013/11/21 11:13 AM
                    3-TFlops-DGEMMMichael S2013/11/21 02:34 PM
                  3-TFlops-DGEMMEric2013/11/22 02:10 AM
                    3-TFlops-DGEMMMichael S2013/11/22 04:41 AM
                    A (not very sensible) alternative: FMADD + FADDPaul A. Clayton2013/11/22 08:19 AM
                  3-TFlops-DGEMMSylvain Collange2013/11/24 02:37 AM
                    3-TFlops-DGEMMMichael S2013/11/24 06:06 AM
                      3-TFlops-DGEMMSylvain Collange2013/11/24 09:28 AM
        HPC guys score FLOPS non-obviouslyPatrick Chase2013/11/23 02:58 PM
  Knights Landing CPU SpeculationPaul Caheny2013/11/18 01:25 PM
    Knights Landing CPU SpeculationKonrad Schwarz2013/11/19 12:24 AM
  Knights Landing CPU SpeculationAmiba Gelos2013/11/19 07:36 PM
    Knights Landing CPU SpeculationDavid Kanter2013/11/20 09:52 AM
    Knights Landing CPU SpeculationLinus Torvalds2013/11/21 02:12 PM
      Knights Landing CPU SpeculationAmiba Gelos2013/11/21 05:14 PM
      Knights Landing CPU SpeculationPatrick Chase2013/11/23 03:33 PM
        Knights Landing CPU SpeculationLinus Torvalds2013/11/25 11:29 AM
          Knights Landing CPU SpeculationLinus Torvalds2013/11/25 12:05 PM
          Knights Landing CPU SpeculationPatrick Chase2013/11/25 12:22 PM
            Knights Landing CPU SpeculationLinus Torvalds2013/11/26 10:11 AM
          Knights Landing CPU SpeculationEric2013/11/26 03:05 AM
            Knights Landing CPU SpeculationEric2013/11/26 03:15 AM
            Knights Landing CPU Speculationnone2013/11/26 03:33 AM
              Knights Landing CPU SpeculationEric2013/11/26 06:30 PM
                Knights Landing CPU SpeculationEric2013/11/26 06:34 PM
                  What is MCDRAM?anon2013/11/26 08:58 PM
                    What is MCDRAM?none2013/11/27 01:00 AM
                      What is MCDRAM?Klimax2013/11/27 02:19 AM
                  Knights Landing CPU SpeculationKlimax2013/11/26 11:06 PM
                Knights Landing CPU SpeculationKlimax2013/11/26 11:05 PM
            Knights Landing CPU Speculationanon2013/11/26 05:53 AM
              Knights Landing CPU Speculationnone2013/11/26 06:20 AM
                Knights Landing CPU SpeculationMichael S2013/11/26 08:06 AM
                  Knights Landing CPU Speculationnone2013/11/26 09:18 AM
                    Knights Landing CPU SpeculationEric Bron2013/11/26 01:21 PM
                      Knights Landing CPU SpeculationEric Bron2013/11/26 01:27 PM
                        Knights Landing CPU Speculationnone2013/11/26 02:26 PM
                    Knights Landing CPU Speculationanon2013/11/26 05:42 PM
                      Knights Landing CPU Speculationnone2013/11/27 01:08 AM
                        Knights Landing CPU Speculationanon2013/11/27 01:50 AM
                          Knights Landing CPU Speculationnone2013/11/27 01:58 AM
                      Knights Landing CPU SpeculationMichael S2013/11/27 01:25 AM
                        Knights Landing CPU Speculationanon2013/11/27 02:32 AM
                          Knights Landing CPU SpeculationMichael S2013/11/27 03:08 AM
    Knights Landing CPU SpeculationChung Leong2013/11/27 01:28 AM
      Knights Landing CPU SpeculationMichael S2013/11/27 02:53 AM
        Knights Landing CPU SpeculationChung Leong2013/11/27 01:03 PM
  BiG.LiTTLe for KNL?Jeff K2013/11/22 06:17 AM
    BiG.LiTTLe for KNL?Patrick Chase2013/11/23 02:54 PM
      BiG.LiTTLe for KNL?Patrick Chase2013/11/23 03:01 PM
  Transactional memoryPatrick Chase2013/11/23 02:37 PM
    Transactional memoryBhima2013/11/25 07:01 AM
      Transactional memoryPatrick Chase2013/11/25 11:52 AM
  Knights Landing CPU SpeculationDaniel2013/11/25 02:17 AM
    Knights Landing CPU SpeculationKlimax2013/11/25 03:12 AM
    Knights Landing CPU Speculationnone2013/11/25 04:05 AM
      Knights Landing CPU SpeculationKlimax2013/11/25 04:45 AM
        Knights Landing CPU Speculationnone2013/11/25 04:55 AM
          Knights Landing CPU Speculationgmb2013/11/25 07:21 AM
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