Cray MTA avoided caches

By: dmcq (, May 20, 2021 10:09 am
Room: Moderated Discussions
Paul A. Clayton ( on May 20, 2021 6:36 am wrote:
> Romain Dolbeau ( on May 19, 2021 4:05 am wrote:
> > Little Horn ( on May 17, 2021 5:03 pm wrote:
> > > Thoughts?
> >
> > Long before I reached the end of the paper (my bad, I know), the Cray MTA (formerly
> > Tera) architecture came back to my mind... Massive multithreading didn't work
> > then, didn't immediately see a reason why it would work today...
> Cray MTA avoided caches (which also assumes word-granular memory interfaces, implying a greater command
> overhead and narrow memory channels (to support dense high-bandwidth DRAM using long bursts)). I
> have not attentively read the paper, but it does assume caches and seems to assume a thread switch
> latency of up to tens of cycles (compared to MTA's any thread immediately executable).
> (There was also no mention of MIPS MT Application Specific Extension, which did slightly
> distinguish between a thread context and a virtual processing element.)
> I had composed a partial response to the original post, but now I think I will try to actually read
> the paper (and the responses here) and compose a more considered response. From what I have read, the
> authors seem to lack familiarity with hardware designs (particularly the GPU description and no mention
> of 3D register files). I like the general idea of hardware having a larger role in thread scheduling,
> but it seemed (from cursory reading) that the specific proposal was not well-thought-out.

I don't know about the Cray design but it seems to me from what's described that it was based on the principle of a GPU, slower but much wider allowing lots of data to get around to where it is needed. A good choice for large computational problems.

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TopicPosted ByDate
A Case Against (Most) Context SwitchesLittle Horn2021/05/17 05:03 PM
  A Case Against (Most) Context Switchesrwessel2021/05/17 06:55 PM
  A Case Against (Most) Context SwitchesFoo_2021/05/18 01:58 AM
    A Case Against (Most) Context SwitchesDoug S2021/05/18 08:45 AM
      A Case Against (Most) Context SwitchesKonrad Schwarz2021/05/19 07:35 AM
  A Case Against (Most) Context SwitchesEtienne Lorrain2021/05/18 03:11 AM
  A Case Against (Most) Context SwitchesAndrey2021/05/18 06:58 AM
  A Case Against (Most) Context Switchesgallier22021/05/18 08:41 AM
  A Case Against (Most) Context Switches---2021/05/18 09:00 AM
  A Case Against That Other PaperBrendan2021/05/18 12:37 PM
    A Case Against That Other PaperMark Roulo2021/05/18 03:32 PM
      A Case Against That Other PaperBrendan2021/05/18 11:05 PM
        A Case Against That Other PaperMark Roulo2021/05/19 01:09 PM
  A Case Against (Most) Context SwitchesRomain Dolbeau2021/05/19 04:05 AM
    A Case Against (Most) Context SwitchesBjörn Ragnar Björnsson2021/05/19 01:13 PM
      A Case Against ... authors show zero awareness of Cray-MTABjörn Ragnar Björnsson2021/05/19 06:18 PM
    Cray MTA avoided cachesPaul A. Clayton2021/05/20 06:36 AM
      Cray MTA avoided cachesdmcq2021/05/20 10:09 AM
        Cray MTA avoided cachesRayla2021/05/20 10:28 AM
      A LONG response to the paperPaul A. Clayton2021/05/22 06:15 AM
        A LONG response to the paperAdrian2021/05/22 09:18 AM
          Thank you for the note of appreciationPaul A. Clayton2021/05/24 05:06 AM
  A Case Against (Most) Context Switchesdmcq2021/05/19 01:47 PM
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