M1 GPU has higher FP32 than A-series GPUs

By: Jeff S. (fakity.delete@this.fake.com), December 7, 2020 10:29 pm
Room: Moderated Discussions
K.K. (anon.delete@this.anon.com) on December 7, 2020 1:32 am wrote:
> I would hypothesize that it's the other way around and that A14 and other mobile GPUs simply take
> longer to execute FP32 operations. My tests so far seem to suggest that both FP32 and FP16 operations
> on M1 can be issued every cycle, with execution latency of two cycles. Maybe mobile GPUs need four
> cycles instead to do a single FP32 operation and Apple has tweaked the M1 to bring the FP32 performance
> up to the level of the FP16? I will run some tests on an A14 later this week.

The main reason the "fp32 got better" angle sounds difficult to believe is that GPUs are typically bottlenecked by operand supply. This is the whole reason ML/neural/tensor engines throw power and area at FMAs hardwired to do just GEMM slice acceleration: you just can't get competitive density if you need two or three RF arrays and ports for every FMA unit, so you chain everything up to do that one thing.

An SIMD FPU that has the same FLOPS for fp32 as fp16 is just wasting half of its scarcest resource in the latter case. While packed fp16 doesn't come for free in power/area (or even programming model simplicity), it's still a small marginal cost over the fp32 unit and the RF.

The alternative is that Apple pulled a consumer Ampere and added double fp32 issue per SIMT thread. Given how many architectural generations it has taken Nvidia to work towards this (moving from quad single-ported RF banks to dual, dual-ported, trying dual int32/fp32 issue, etc.) and still taking a huge efficiency hit in general purpose programs' fp32 utilization vs. theoretical limits, I think it's unrealistic to imagine Apple did it all in one step perfectly somehow.
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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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