AVX-512 possibly in its own clock domain?

By: Maynard Handley (name99.delete@this.name99.org), August 26, 2018 4:35 pm
Room: Moderated Discussions
David Hess (davidwhess.delete@this.gmail.com) on August 26, 2018 10:20 am wrote:
> Brett (ggtgp.delete@this.yahoo.com) on August 25, 2018 1:58 pm wrote:
> >
> > There is also no law that the float/vector unit has to run at the same clock rate as the rest of the CPU.
> > You just have to buffer the cache interface and the incoming decoded float/vector instruction
> > stream, and buffer the incoming instruction completion signals for write commits.
> >
> > This would completely hide single slow vector instructions, you could detect this
> > by having say every 20th instruction a vector op, the CPU should stay at 4+GHz.
>
> I thought they might operate it synchronously at a small integer fraction of the clock
> speed like 2/3 or 4/5 instead of changing the clock speed of the entire core.
>

And that certainly has happened in the past!
Some of the PPCs (around say the PPC 750) had some sort of weird stutter, I can't remember the details, that meant that every sixth or fifth FP instruction was delayed by one cycle. This was "architected" in the sense that it was meant to happen, every n'th instruction (or perhaps every n'th clock) was devoted to what ever it was that took some cleanup, it wasn't an artifact of a particular sequence of FP instructions or data.

With a brief search the best I can find is this which references the issue:
https://cr.yp.to/hardware/ppc.html
At the time I did know the details, but it's possible I learned them from reading internal Apple docs and they were never public? Oh well.
< Previous Post in ThreadNext Post in Thread >
TopicPosted ByDate
AVX-512 downclocking not as bad as thought?Travis2018/08/24 12:01 AM
  AVX-512 downclocking not as bad as thought?Ricardo B2018/08/24 04:22 AM
    AVX-512 downclocking not as bad as thought?David Hess2018/08/24 09:08 PM
      AVX-512 downclocking not as bad as thought?Travis2018/08/24 09:54 PM
        AVX-512 downclocking not as bad as thought?anon2018/08/25 04:06 AM
          AVX-512 downclocking not as bad as thought?Travis2018/08/25 07:34 PM
        AVX-512 downclocking not as bad as thought?David Hess2018/08/25 09:44 AM
          AVX-512 downclocking not as bad as thought?Travis2018/08/25 07:35 PM
  AVX-512 downclocking not as bad as thought?Jeff S.2018/08/24 06:22 AM
    AVX-512 downclocking not as bad as thought?Travis2018/08/24 07:41 AM
      AVX-512 downclocking not as bad as thought?Jeff S.2018/08/24 09:24 AM
  AVX-512 downclocking not as bad as thought?Maynard Handley2018/08/24 11:03 AM
    AVX-512 downclocking not as bad as thought?Jeff S.2018/08/24 11:24 AM
      AVX-512 downclocking not as bad as thought?Maynard Handley2018/08/24 12:26 PM
        AVX-512 downclocking not as bad as thought?Jeff S.2018/08/24 12:39 PM
        AVX-512 downclocking not as bad as thought?megabytephreak2018/08/24 12:43 PM
          AVX-512 downclocking not as bad as thought?Maynard Handley2018/08/24 03:59 PM
          AVX-512 downclocking not as bad as thought?someone2018/09/12 12:20 AM
            AVX-512 downclocking not as bad as thought?anonymou52018/09/12 06:39 AM
        AVX-512 downclocking not as bad as thought?Travis2018/08/24 02:48 PM
    AVX-512 downclocking not as bad as thought?David Hess2018/08/24 09:26 PM
  Gold 6130 resultsTravis2018/08/24 03:49 PM
    Gold 6130 results-.-2018/08/24 08:08 PM
      Gold 6130 resultsTravis2018/08/24 10:02 PM
        Gold 6130 results-.-2018/08/25 02:27 AM
          Gold 6130 resultsTravis2018/08/25 07:37 PM
  AVX-512 downclocking not as bad as thought?Adrian2018/08/24 08:30 PM
    AVX-512 downclocking not as bad as thought?Adrian2018/08/24 08:36 PM
      AVX-512 downclocking not as bad as thought?Adrian2018/08/24 08:39 PM
        AVX-512 downclocking not as bad as thought?Travis2018/08/24 10:06 PM
          AVX-512 downclocking not as bad as thought?Adrian2018/08/24 10:28 PM
  AVX-512 downclocking not as bad as thought?Royi2018/08/25 03:36 AM
    AVX-512 downclocking not as bad as thought?Travis Downs2018/08/25 08:18 AM
      AVX-512 possibly in its own clock domain?Brett2018/08/25 12:58 PM
        AVX-512 possibly in its own clock domain?Travis2018/08/25 07:40 PM
          AVX-512 possibly in its own clock domain?Brett2018/08/26 08:48 AM
            AVX-512 possibly in its own clock domain?Maynard Handley2018/08/26 04:28 PM
              AVX-512 possibly in its own clock domain?none2018/08/26 08:40 PM
                AVX-512 possibly in its own clock domain?Maynard Handley2018/08/27 09:37 AM
                  AVX-512 possibly in its own clock domain?none2018/08/27 10:28 AM
        AVX-512 possibly in its own clock domain?David Hess2018/08/26 09:20 AM
          AVX-512 possibly in its own clock domain?Maynard Handley2018/08/26 04:35 PM
            AVX-512 possibly in its own clock domain?Gabriele Svelto2018/08/27 12:46 PM
            AVX-512 possibly in its own clock domain?David Hess2018/08/27 06:03 PM
  AVX-512 downclocking not as bad as thought?Travis2018/09/07 07:32 PM
    AVX-512 downclocking not as bad as thought?anonymou52018/09/07 08:03 PM
      AVX-512 downclocking not as bad as thought?Travis2018/09/09 07:16 PM
    AVX-512 downclocking not as bad as thought?Tim McCaffrey2018/09/08 07:55 AM
      AVX-512 downclocking not as bad as thought?Travis Downs2018/09/08 02:21 PM
Reply to this Topic
Name:
Email:
Topic:
Body: No Text
How do you spell avocado?