Apple loses a lot by not having turbo and SMT

By: Adrian (a.delete@this.acm.org), November 18, 2020 7:23 am
Room: Moderated Discussions
TJ (notanemail.delete@this.bla.com) on November 18, 2020 1:10 am wrote:
>
> At least older intel architectures used to gain 10-30% with SMT depending
> on load. But can a very high IPC design like A14/M1 really reach 30%?
> I think there is much less time available where SMT can be active in A14/M1. I think the efficiency
> cores gives a better multi-thread boost than SMT with not too much worse power efficiency.
> The efficiency cores requires a bit more transistors though compared to adding SMT in the
> big cores, but efficiency cores are still needed for power efficiency during low loads.
>
> My guess is that Apple never adds SMT due to complexity, security and diminishing return reasons.
>


While we do not know with certainty the micro-architectures of the Apple CPUs and how efficiently their various execution units are used in various typical applications, filling the execution units with reordered instructions taken from a single-thread or with instructions taken from independent concurrent threads are the 2 ways of achieving high-utilization for the execution units.

A CPU that is very successful at the first method is unlikely to gain much from also applying the second method.

So even if we do not really have the information required to know this for sure, I agree with TJ, that it is likely that the Apple CPUs would not gain much from SMT so it might not be worthwhile for them to add it.

Anyway, their engineers must have all the data, from execution traces, to estimate any possible benefits, so if there are any, some future CPU model will add it.

For now, a Ryzen 7 4700U, without SMT, is mostly below M1, while a Ryzen 7 4800U, with SMT, is mostly above M1, so it is helped by SMT.






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TopicPosted ByDate
1st round of M1 GPU benchmarksMaynard Handley2020/11/16 12:46 PM
  1st round of M1 GPU benchmarksAdrian2020/11/16 01:02 PM
    1st round of M1 GPU benchmarksI_vs2020/11/17 01:18 AM
  1st round of M1 GPU benchmarksRType2020/11/16 01:06 PM
    1st round of M1 GPU benchmarksMaynard Handley2020/11/16 01:45 PM
      And the NZ'ers are first to deliver cinebench scoresMaynard Handley2020/11/16 02:58 PM
        And the NZ'ers are first to deliver cinebench scoresWill2020/11/16 03:30 PM
          re: "scaling"Dummond D. Slow2020/11/16 04:06 PM
            re: "scaling"Maynard Handley2020/11/16 04:29 PM
              re: "scaling"Dummond D. Slow2020/11/16 04:51 PM
                re: "scaling"Maynard Handley2020/11/16 05:51 PM
                  re: "scaling"Dummond D. Slow2020/11/16 06:22 PM
                    re: "scaling"Maynard Handley2020/11/16 06:23 PM
                      re: "scaling"Maynard Handley2020/11/16 06:27 PM
                        re: "scaling"Dummond D. Slow2020/11/16 06:37 PM
                          re: "scaling"Chester2020/11/16 08:25 PM
                          Actual power consumption values.Dummond D. Slow2020/11/17 07:05 AM
                    re: "scaling"Doug S2020/11/17 10:25 AM
                      Apple loses a lot by not having turbo and SMTDummond D. Slow2020/11/17 11:18 AM
                        Apple loses a lot by not having turbo and SMTDoug S2020/11/17 12:21 PM
                          Apple loses a lot by not having turbo and SMTblaine2020/11/19 05:18 PM
                            Apple loses a lot by not having turbo and SMTDummond D. Slow2020/11/19 05:31 PM
                        Apple loses a lot by not having turbo and SMTTJ2020/11/18 01:10 AM
                          Cinebench is NOT a representation of average workloadsAndrei F2020/11/18 05:21 AM
                            SPEC is NOT a representation of average workloadsChester2020/11/18 07:02 AM
                              SPEC is NOT a representation of average workloadsDummond D. Slow2020/11/18 07:17 AM
                                SPEC is NOT a representation of average workloadsnone2020/11/18 08:18 AM
                                  x264 without SIMD is nonsenseDummond D. Slow2020/11/18 08:31 AM
                                  SPEC is NOT a representation of average workloadsMaynard Handley2020/11/18 09:13 AM
                                    SPEC is NOT a representation of average workloadsDummond D. Slow2020/11/18 09:21 AM
                                      SPEC is NOT a representation of average workloadsWilco2020/11/18 09:42 AM
                                        role of hand-optimized assembly in multimedia encodersDummond D. Slow2020/11/18 11:06 AM
                                          role of hand-optimized assembly in multimedia encodersdifferent anon2020/11/18 01:27 PM
                                            role of hand-optimized assembly in multimedia encodersDummond D. Slow2020/11/18 02:47 PM
                                              role of hand-optimized assembly in multimedia encodersDummond D. Slow2021/05/18 12:29 PM
                                          role of hand-optimized assembly in multimedia encodersRichardC2020/11/18 03:42 PM
                                          role of hand-optimized assembly in multimedia encodersnone2020/11/19 07:17 AM
                                      SPEC is NOT a representation of average workloadsnone2020/11/18 10:14 AM
                                        SPEC is NOT a representation of average workloadsDummond D. Slow2020/11/18 11:17 AM
                                      SPEC is NOT a representation of average workloadsMaynard Handley2020/11/18 11:03 AM
                                        SPEC is NOT a representation of average workloadsDummond D. Slow2020/11/18 11:25 AM
                                          SPEC is NOT a representation of average workloadsMaynard Handley2020/11/18 12:03 PM
                                            SPEC is NOT a representation of average workloadsDummond D. Slow2020/11/18 02:57 PM
                                              SPEC is NOT a representation of average workloadsMaynard Handley2020/11/18 04:36 PM
                                                SPEC is NOT a representation of average workloadsDummond D. Slow2020/11/18 04:50 PM
                                                  SPEC is NOT a representation of average workloadsDoug S2020/11/19 09:13 AM
                                                    SPEC is NOT a representation of average workloads-.-2020/11/19 02:34 PM
                                                    SPEC is NOT a representation of average workloadsDummond D. Slow2020/11/19 02:35 PM
                                              SPEC is NOT a representation of average workloadsEtienne Lorrain2020/11/19 04:04 AM
                                                SPEC is NOT a representation of average workloadsDummond D. Slow2020/11/19 05:58 AM
                                SPEC is NOT a representation of average workloadsChester2020/11/18 02:06 PM
                                  about bitratesDummond D. Slow2020/11/18 03:04 PM
                                    about bitratesChester2020/11/19 02:45 PM
                                  SPEC is NOT a representation of average workloadsOok2020/11/18 03:05 PM
                                    SPEC is NOT a representation of average workloadsDummond D. Slow2020/11/18 03:21 PM
                                  SPEC is NOT a representation of average workloadsNoSpammer2020/11/19 06:48 AM
                              SPEC is NOT a representation of average workloadsAndrei F2020/11/18 07:44 AM
                                SPEC is NOT a representation of average workloadsDummond D. Slow2020/11/18 07:48 AM
                                  SPEC is NOT a representation of average workloadsAdrian2020/11/18 08:15 AM
                                    SPEC is NOT a representation of average workloadsDummond D. Slow2020/11/18 08:41 AM
                                      SPEC is NOT a representation of average workloadsAdrian2020/11/18 09:04 AM
                                        SPEC is NOT a representation of average workloadsDummond D. Slow2020/11/18 09:32 AM
                                          SPEC is NOT a representation of average workloadsAdrian2020/11/18 10:26 AM
                                    SPEC is NOT a representation of average workloadsMaynard Handley2020/11/18 09:22 AM
                                      SPEC is NOT a representation of average workloadsAdrian2020/11/18 10:28 AM
                                  SPEC is NOT a representation of average workloadsAndrei F2020/11/18 08:34 AM
                                    SPEC is NOT a representation of average workloadsDummond D. Slow2020/11/18 09:00 AM
                                    SPEC is NOT a representation of average workloadsChester2020/11/18 02:18 PM
                                    SPEC is NOT a representation of average workloadsJukka Larja2020/11/20 08:03 AM
                                SPEC is NOT a representation of average workloadsChester2020/11/18 02:13 PM
                              SPEC is NOT a representation of average workloadsnone2020/11/18 08:07 AM
                                SPEC is NOT a representation of average workloadsMichael S2020/11/18 01:33 PM
                                  Interesting, thanks! (NT)none2020/11/19 07:03 AM
                            Cinebench is NOT a representation of average workloadsrwessel2020/11/18 07:03 AM
                              Cinebench is NOT a representation of average workloadsDoug S2020/11/18 07:44 AM
                                Cinebench is NOT a representation of average workloadsDummond D. Slow2020/11/18 07:52 AM
                                  Cinebench is NOT a representation of average workloadsDoug S2020/11/18 02:59 PM
                                    Cinebench is NOT a representation of average workloadsDummond D. Slow2020/11/18 03:12 PM
                                      Cinebench is NOT a representation of average workloadsDoug S2020/11/19 09:19 AM
                                        Cinebench is NOT a representation of average workloadsDummond D. Slow2020/11/19 03:03 PM
                                          Cinebench is NOT a representation of average workloadsUngo2020/11/19 08:12 PM
                                            Cinebench is NOT a representation of average workloadsDummond D. Slow2020/11/20 08:45 AM
                                It's not really SMT or adding small coresDummond D. Slow2020/11/18 07:58 AM
                                  It's not really SMT or adding small coresDoug S2020/11/18 03:02 PM
                                    It's not really SMT or adding small coresDummond D. Slow2020/11/18 03:27 PM
                                Cinebench is NOT a representation of average workloadsxyz2020/11/18 12:14 PM
                                  Cinebench is NOT a representation of average workloadsMaynard Handley2020/11/18 12:54 PM
                                    Cinebench is NOT a representation of average workloadsGabriele Svelto2020/11/18 01:41 PM
                                      Cinebench is NOT a representation of average workloadsMaynard Handley2020/11/18 01:52 PM
                                        Cinebench is NOT a representation of average workloadsGabriele Svelto2020/11/18 02:05 PM
                            Cinebench is NOT a representation of average workloadsTJ2020/11/18 11:46 AM
                            SMT shines in IO heavy & commercial DB workloadsxyz2020/11/18 12:05 PM
                            "Average workloads" don't exist (NT)Foo_2020/11/19 02:55 AM
                          Apple loses a lot by not having turbo and SMTDummond D. Slow2020/11/18 07:02 AM
                            Apple loses a lot by not having turbo and SMTMaynard Handley2020/11/18 08:37 AM
                              Apple loses a lot by not having turbo and SMTDummond D. Slow2020/11/18 08:55 AM
                              Apple loses a lot by not having turbo and SMTDavid Hess2020/11/18 12:12 PM
                                Apple loses a lot by not having turbo and SMTMaynard Handley2020/11/18 01:12 PM
                                  Apple loses a lot by not having turbo and SMTJörn Engel2020/11/18 04:04 PM
                                    Apple loses a lot by not having turbo and SMTanonymou52020/11/18 04:37 PM
                                      Apple loses a lot by not having turbo and SMTJörn Engel2020/11/19 03:28 AM
                                  Apple loses a lot by not having turbo and SMTDavid Hess'2020/11/19 06:25 PM
                          Apple loses a lot by not having turbo and SMTAdrian2020/11/18 07:23 AM
                            Apple loses a lot by not having turbo and SMTgallier22020/11/18 11:21 PM
                              Apple loses a lot by not having turbo and SMTJames2020/11/19 01:22 AM
                                Apple loses a lot by not having turbo and SMTWilco2020/11/19 04:06 AM
                              Apple loses a lot by not having turbo and SMTanonymou52020/11/19 01:34 AM
                                Apple loses a lot by not having turbo and SMTgallier22020/11/19 08:04 AM
                                  big.LITTLE with different ISAsJames2020/11/19 08:41 AM
                                    big.LITTLE with different ISAsgallier22020/11/20 02:36 AM
                                    big.LITTLE with different ISAsanon2020/11/20 12:31 PM
                              Apple loses a lot by not having turbo and SMTAdrian2020/11/19 01:56 AM
                        Apple loses a lot by not having turbo and SMTJon Masters2020/11/18 11:46 AM
                          Apple loses a lot by not having turbo and SMTanonymou52020/11/18 02:41 PM
                          Apple loses a lot by not having turbo and SMTDummond D. Slow2020/11/18 03:17 PM
                            Apple loses a lot by not having turbo and SMTMaynard Handley2020/11/18 04:46 PM
                              Apple loses a lot by not having turbo and SMTJon Masters2020/11/18 11:31 PM
                                Apple loses a lot by not having turbo and SMTDummond D. Slow2020/11/19 06:01 AM
                              Apple loses a lot by not having turbo and SMTAdrian2020/11/19 01:50 AM
                                Apple loses a lot by not having turbo and SMTAdrian2020/11/19 02:10 AM
                                Apple loses a lot by not having turbo and SMTMaynard Handley2020/11/19 09:13 AM
                                  Apple loses a lot by not having turbo and SMTDummond D. Slow2020/11/19 03:10 PM
                        Apple loses a lot by not having turbo and SMTjuanrga2020/11/19 01:49 AM
                    re: "scaling"sr2020/11/17 11:39 AM
                      re: "scaling"Adrian2020/11/17 12:41 PM
                        re: "scaling"Adrian2020/11/17 12:52 PM
                          re: "scaling"Chester2020/11/17 05:29 PM
                  re: "scaling"anonymou52020/11/16 07:18 PM
                    re: "scaling"Maynard Handley2020/11/16 07:44 PM
        And the NZ'ers are first to deliver cinebench scoresDummond D. Slow2020/11/16 04:12 PM
          And the NZ'ers are first to deliver cinebench scoresMaynard Handley2020/11/16 04:31 PM
            And the NZ'ers are first to deliver cinebench scoresDummond D. Slow2020/11/16 04:46 PM
        And the NZ'ers are first to deliver cinebench scoresMaynard Handley2020/11/16 06:04 PM
          And the NZ'ers are first to deliver cinebench scoresDummond D. Slow2020/11/16 06:28 PM
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    1st round of M1 GPU benchmarksChester2020/11/16 08:17 PM
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      Phoronix Mac mini M1 benchPaul2020/11/25 02:08 AM
        Phoronix Mac mini M1 benchPaul2020/11/25 02:12 AM
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