Shared FPU wasn't BD's problem

By: David Kanter (, August 30, 2021 10:29 pm
Room: Moderated Discussions
Chester ( on August 30, 2021 1:03 pm wrote:
> -.- ( on August 29, 2021 4:05 am wrote:
> > ARM's upcoming Cortex A510 uses a shared FPU between two cores, so there's
> > at least a second mainstream player trying out shared FPUs:
> >
> >
> >
> > I recall Bulldozer had minimum 2 cycle latency FPU ops, and current
> > ARM chips generally also have minimum 2 cycle latency FPU ops.
> In BD's case, that's probably to hit high clock speeds on a pretty bad node. Integer SIMD
> ops are 1c latency on newer AMD CPUs, but probably 2c in Bulldozer because the units are
> half width. Piledriver could do a couple FPU ops (extrq, insertq) with 1c latency.
> Sharing an AVX512 unit between 4 little cores may work, in a way similar to Apple AMX,
> A510 SVE, and IBM Telum's AI accelerator. I think Bulldozer's biggest problems were:
> - The 16 KB L1D was too small and write-through
> - Slow L2 has to handle a lot of L1D misses

Also, it could only do a single L2 access/clock IIRC. It probably needed to be able to do 3 given the write-through.

< Previous Post in ThreadNext Post in Thread >
TopicPosted ByDate
AVX512 as co-processorMichael S2021/08/29 03:13 AM
  AVX512 as co-processor-.-2021/08/29 04:05 AM
    Shared FPU wasn't BD's problemChester2021/08/30 01:03 PM
      Excellent post (NT)Heikki Kultala2021/08/30 01:34 PM
      Shared FPU wasn't BD's problemP Snip2021/08/30 01:53 PM
      Shared FPU wasn't BD's problem-.-2021/08/30 05:47 PM
      Shared FPU wasn't BD's problemDavid Kanter2021/08/30 10:29 PM
        Shared FPU wasn't BD's problemChester2021/08/31 02:58 AM
          Shared FPU wasn't BD's problemDavid Kanter2021/08/31 09:28 AM
            Shared FPU wasn't BD's problemChester2021/08/31 12:29 PM
            Shared FPU wasn't BD's problemRayla2021/08/31 02:34 PM
      Shared FPU wasn't BD's problemAnon2021/08/31 12:28 AM
        Shared FPU wasn't BD's problemAdrian2021/08/31 01:27 AM
          Shared FPU wasn't BD's problemAnon2021/08/31 02:06 AM
            Shared FPU wasn't BD's problemanonymou52021/08/31 02:09 PM
              Shared FPU wasn't BD's problemChester2021/09/01 11:05 AM
      Shared FPU wasn't BD's problemKevin G2021/08/31 09:39 AM
        Shared FPU wasn't BD's problemChester2021/09/01 10:03 AM
Reply to this Topic
Body: No Text
How do you spell tangerine? 🍊