M1 GPU has higher FP32 than A-series GPUs

By: Adrian (a.delete@this.acm.org), December 9, 2020 2:36 am
Room: Moderated Discussions
K.K. (anon.delete@this.anon.com) on December 9, 2020 12:35 am wrote:
>
> Thanks for explaining this! I know absolutely nothing about circuitry
> implementation, so your explanation was enlightening.
>
> At any rate, I managed to find an iPhone 12 to run my benchmark,
> and I have also fixed a bug with timings. Here are the results:
>
> iPhone 12 (A14 with 4-core GPU)
> --------------------------------
> float1 638.0
> float2 645.0
> float3 645.0
> float4 646.0
> half1 1282.0
> half2 1297.0
> half3 1296.0
> half4 1298.0
>
> MacBook Pro (M1 with 8-core GPU)
> --------------------------------
> float1 2458.0
> float2 2528.0
> float3 2508.0
> float4 2522.0
> half1 2569.0
> half2 2592.0
> half3 2594.0
> half4 2597.0
>
> These results suggest that Apple indeed managed to improve the throughput of FP32 without sacrificing
> anything else. Also, I don't see any evidence that they implement dual-issue or anything comparable
> — it's just a regular FMA per cycle on 1024 (M1) or 512 (A14) ALUs running at around 1.3ghz. The
> A14 simply has half the FP32 throughput. My amateur guess would be that Apple's ALUs are historically
> "native" FP16 but also capable of doing a FP32 operation at half the speed (maybe two cycles?). In
> M1, Apple appears to have "upgraded" the ALUs with single-cycle FP32 capability. I have no idea what
> hardware changes are necessary to achieve this. I wouldn't be surprised if the next iteration of Apple
> GPU cores brings dual-rate-per-clock FP16 capability just like current Nvidia and AMD GPUs.


For the purpose of comparison, GPUs are usually classified by their number of FP32 ALUs.

So M1 has a GPU with 1024 FP32 ops per cycle, which is better than both Intel Tiger Lake (with 768) and AMD Renoir (with 512), while Apple A14 has a GPU with 256 FP32 ops per cycle, which is better than standard Intel Skylake GPUs (192), but worse than enhanced (Iris) Intel Skylake GPUs (with 384 or 576 FP32 ops per cycle).


A14 has double-rate FP16 ops, which is most likely achieved by splitting the FP32 ALUs in 2 FP16 ALUs.


M1 has same rate FP16 ops, and that can be achieved in 2 ways, either all the FP32 ALUs also function in a FP16 mode, so each ALU can do either a FP32 op or a FP16 op, or half of the ALUs are simpler and they can do only FP32 ops and they are not used for FP16, while the other half of the ALUs are more complex and they can be split into a double number of FP16 ALUs.


The ambiguous comment from Apple seems to favor the second method of implementation, with 512 simple FP32 ALUs and 512 complex FP32 ALUs.


These 2 implementation methods can be differentiated by doing a benchmark with simultaneous FP16 and FP32 computations.


The first method will yield 1.3 Tflops FP32 + 1.3 Tflops FP16, while the second method would yield 1.3 Tflops FP32 + 2.6 Tflops FP16, unless some other limitation prevents reaching the maximum speed. Based on your previous results, reaching that FP32 speed might need interleaving 2 chains.







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TopicPosted ByDate
M1 GPU microbenchmarks (peak FLOPS)K.K2020/12/05 03:31 AM
  M1 GPU microbenchmarks (peak FLOPS)K.K.2020/12/05 03:57 AM
  M1 GPU microbenchmarks (peak FLOPS)Adrian2020/12/05 04:00 AM
  M1 GPU microbenchmarks (peak FLOPS)Chester2020/12/05 10:39 AM
    M1 GPU microbenchmarks (peak FLOPS)K.K2020/12/06 03:46 AM
  M1 GPU microbenchmarks (peak FLOPS)Maynard Handley2020/12/05 12:12 PM
  M1 GPU has higher FP32 than A-series GPUsAndrei F2020/12/06 03:24 AM
    M1 GPU has higher FP32 than A-series GPUsK.K2020/12/06 03:49 AM
    M1 GPU has higher FP32 than A-series GPUsJeff S.2020/12/06 11:12 PM
      M1 GPU has higher FP32 than A-series GPUsK.K.2020/12/07 02:32 AM
        M1 GPU has higher FP32 than A-series GPUsJeff S.2020/12/07 10:29 PM
          M1 GPU has higher FP32 than A-series GPUsK.K.2020/12/09 01:35 AM
            M1 GPU has higher FP32 than A-series GPUsAdrian2020/12/09 02:36 AM
              M1 GPU has higher FP32 than A-series GPUsK.K.2020/12/09 02:59 AM
                M1 GPU has higher FP32 than A-series GPUsAdrian2020/12/09 03:16 AM
                  M1 GPU has higher FP32 than A-series GPUsK.K2020/12/09 04:56 AM
                    M1 GPU has higher FP32 than A-series GPUsAdrian2020/12/09 05:28 AM
                      M1 GPU has higher FP32 than A-series GPUsK.K2020/12/09 06:01 AM
                        M1 GPU has higher FP32 than A-series GPUsAdrian2020/12/09 06:37 AM
                          and beyond just the flops...anonymou52020/12/09 02:08 PM
                            and beyond just the flops...Doug S2020/12/09 03:06 PM
                              and beyond just the flops...Maynard Handley2020/12/09 04:05 PM
                                and beyond just the flops...Adrian2020/12/09 05:36 PM
                                and beyond just the flops...anonymou52020/12/09 08:28 PM
                                  and beyond just the flops...Maynard Handley2020/12/09 08:40 PM
                                    and beyond just the flops...anonymou52020/12/10 02:18 AM
                                      and beyond just the flops...anonymou52020/12/10 02:51 AM
                                      and beyond just the flops...Maynard Handley2020/12/10 09:53 AM
                                        and beyond just the flops...Megol2020/12/10 10:57 AM
                                          and beyond just the flops...Maynard Handley2020/12/10 12:16 PM
                                            and beyond just the flops...anonymou52020/12/10 04:12 PM
                                              and beyond just the flops...anonymou52020/12/10 04:24 PM
                                                and beyond just the flops...Maynard Handley2020/12/10 06:18 PM
                                                  and beyond just the flops...Maynard Handley2020/12/10 06:23 PM
                                                    and beyond just the flops...anonymou52020/12/10 09:59 PM
                                                    and beyond just the flops...Gabriele Svelto2020/12/11 01:57 AM
                                                      and beyond just the flops...Dummond D. Slow2020/12/11 09:52 AM
                                                        and beyond just the flops...Maynard Handley2020/12/11 09:57 AM
                                                          and beyond just the flops...Dummond D. Slow2020/12/11 10:00 AM
                                                            and beyond just the flops...Maynard Handley2020/12/11 11:22 AM
                                                              and beyond just the flops...Dummond D. Slow2020/12/12 09:13 AM
                                                                and beyond just the flops...Maynard Handley2020/12/12 01:41 PM
                                                                  and beyond just the flops...Dummond D. Slow2020/12/12 03:35 PM
                                                  and beyond just the flops...Dummond D. Slow2020/12/11 09:41 AM
                                                    and beyond just the flops...Maynard Handley2020/12/11 10:01 AM
                                                      and beyond just the flops...Dummond D. Slow2020/12/11 10:23 AM
                                                        and beyond just the flops...Dummond D. Slow2020/12/11 10:24 AM
                                              and beyond just the flops...Adrian2020/12/11 01:37 AM
                                                and beyond just the flops...Adrian2020/12/11 02:59 AM
                                                and beyond just the flops...Ungo2020/12/11 03:39 AM
                                                and beyond just the flops...Maynard Handley2020/12/11 10:07 AM
                                                  and beyond just the flops...Adrian2020/12/11 11:39 AM
                                                    and beyond just the flops...anonymou52020/12/11 03:01 PM
                                                    and beyond just the flops...David Hess2020/12/12 08:17 AM
                                                      and beyond just the flops...Jukka Larja2020/12/12 11:08 AM
                                                        and beyond just the flops...David Hess2020/12/12 11:36 AM
                                                          and beyond just the flops...Jukka Larja2020/12/12 09:45 PM
                                                            and beyond just the flops...David Hess2020/12/13 06:59 PM
                                                        and beyond just the flops...Adrian2020/12/12 03:11 PM
                                                          and beyond just the flops...Adrian2020/12/12 03:21 PM
                                                            and beyond just the flops...David Hess2020/12/13 07:02 PM
                              and beyond just the flops...useruser2020/12/09 09:38 PM
                                and beyond just the flops...anonymou52020/12/10 02:31 AM
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