FMACs can be ganged together, confirmed already by JF (link inside) -- Oh No JF

Article: AMD's Bulldozer Microarchitecture
By: Fritz (fritz.muller.delete@this.gmail.com), September 22, 2010 4:37 am
Room: Moderated Discussions
Alex (no@spam.org) on 9/9/10 wrote:
---------------------------
>David wrote in his article:
>
>> However, it is possible that Bulldozer's two symmetric FMAC
>> units could be ganged together to execute both halves of an
>> AVX instruction simultaneously to reduce latency.
>
>This sounds rather vague. However it was already confirmed by John Fruehe of AMD in an post at amdzone:
>
>> Interlagos = 8 256-bit FPUs. When running non-AVX code, they are 16 128-bit
>>FPUs; we have "Flex FPU" which allows a 256-bit unit to be scheduled as 2 128-bit FMACs.
>
>Thanks again for a great article.
>

Fruehe interprets it in an odd way, though. All available info points clearly to two 128bit units (with their own schedulers, datapaths) that can be ganged up, not a single 256bit unit with some dual-issue scheduler. Right?

Soo in that thread he also makes odd comments about SandyBridge's AVX unit, claiming it's incapable of splitting up to two 128bit units for "legacy" math, claiming Bulldozer superior. While Intel's AVX Programming Reference clearly states that AVX is for (vectors of) single-precision (FP32) and double-precision (FP64) operands... Fruehe seems to think AVX is only for scalar FP256, not (up to) 256bit vectors?

(IMHO, a shining example of why you shouldn't let marketing guys near any forum where their simplifications are taken as technical detail.)
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TopicPosted ByDate
Bulldozer article onlineDavid Kanter2010/08/30 11:44 PM
  Bulldozer article onlineTriskaine2010/08/31 01:14 AM
  Bulldozer article online?2010/08/31 02:39 AM
    Bulldozer article onlinehobold2010/08/31 11:00 AM
    Dispatch groupsDavid Kanter2010/08/31 12:52 PM
      Dispatch groupsIntelUser20002010/08/31 02:40 PM
        Dispatch groupsDavid Kanter2010/08/31 03:22 PM
      Dispatch groupsarb2010/08/31 03:11 PM
        Dispatch groupsredpriest2010/08/31 08:46 PM
      Dispatch groups?2010/09/01 12:41 AM
        Dispatch groupsDavid Kanter2010/09/01 09:15 AM
          Dispatch groups?2010/09/01 10:03 AM
  Bulldozer article onlineAlex2010/08/31 03:45 AM
    Bulldozer article onlineIntelUser20002010/08/31 06:46 AM
      merci (NT)Alex2010/08/31 10:02 AM
    Bulldozer article onlinehobold2010/08/31 10:56 AM
      Bulldozer article onlineDavid Kanter2010/08/31 12:53 PM
  Bulldozer article onlinesomeone2010/08/31 06:09 AM
    Bulldozer article onlineIntelUser20002010/08/31 06:41 AM
      Thanks (NT)someone2010/08/31 06:52 AM
  Bulldozer article onlineRohit2010/08/31 06:13 AM
    Extremely unlikelyDaniel Bizó2010/08/31 03:00 PM
      Bulldozer versus Westmere single threaded performanceMark Roulo2010/08/31 03:35 PM
        Bulldozer versus Westmere single threaded performanceHoward Chu2010/08/31 07:25 PM
        Bulldozer versus Westmere single threaded performanceAndreas2010/09/01 01:01 AM
          Bulldozer versus Westmere single threaded performanceFoo_2010/09/01 02:11 AM
            Bulldozer versus Westmere single threaded performanceJack2010/09/01 10:08 PM
              Bulldozer versus Westmere single threaded performanceslacker2010/09/02 05:59 AM
                Bulldozer versus Westmere single threaded performanceJack2010/09/02 05:14 PM
        Bulldozer versus Westmere single threaded performanceRichard Cownie2010/09/01 04:41 AM
          Bulldozer versus Westmere single threaded performance?2010/09/01 06:10 AM
            Bulldozer versus Westmere single threaded performanceRichard Cownie2010/09/01 08:11 AM
              Bulldozer versus Westmere single threaded performanceDavid Kanter2010/09/01 08:50 AM
          Bulldozer versus Westmere single threaded performanceMark Roulo2010/09/01 09:14 AM
            Bulldozer versus Westmere single threaded performanceRichard Cownie2010/09/01 09:33 AM
      There is no 20% penalty of two threads compared to single core - it's 10%Heikki Kultala2010/09/02 10:39 PM
        There is no 20% penalty of two threads compared to single core - it's 10%Azazel2010/09/03 12:35 AM
          There is no 20% penalty of two threads compared to single core - it's 10%?2010/09/03 02:40 AM
          There is no 20% penalty of two threads compared to single core - it's 10%Heikki Kultala2010/09/03 03:49 AM
            There is no 20% penalty of two threads compared to single core - it's 10%Azazel2010/09/03 07:31 AM
          There is no 20% penalty of two threads compared to single core - it's 10%MS2010/09/03 06:27 AM
          Don't read too much into it...David Kanter2010/09/03 03:14 PM
            Don't read too much into it...DC2010/09/05 11:07 AM
  Bulldozer article onlineIan Ollmann2010/08/31 05:07 PM
    Bulldozer article onlineMatt Waldhauer2010/09/05 04:10 AM
      Bulldozer article onlinehobold2010/09/05 08:19 AM
        Bulldozer article onlineDC2010/09/05 11:12 AM
          Bulldozer article onlineMichael S2010/09/05 12:27 PM
            Bulldozer article onlineBrett2010/09/05 03:01 PM
          Bulldozer article onlinesomeone2010/09/05 01:56 PM
            Bulldozer article onlineAlex2010/09/05 02:59 PM
              Bulldozer article onlinesomeone2010/09/05 03:05 PM
                Bulldozer article onlineDC2010/09/06 07:38 AM
                  Bulldozer article onlinesomeone2010/09/06 08:24 AM
                  Bulldozer article onlineDavid Kanter2010/09/06 05:12 PM
                    Bulldozer article onlineEduardoS2010/09/06 06:21 PM
                    Bulldozer article onlineanon2010/09/06 06:26 PM
                      Bulldozer article onlineDavid Kanter2010/09/06 07:55 PM
                        Bulldozer article onlineanon2010/09/06 10:49 PM
                          Bulldozer article onlineDavid Kanter2010/09/06 10:57 PM
                            Bulldozer article onlineJack2010/09/07 09:55 PM
                            Bulldozer article onlineslacker2010/09/08 05:53 AM
            Bulldozer article onlineDC2010/09/06 07:43 AM
              Bulldozer article onlineMegol2010/09/06 08:27 AM
              Bulldozer article onlinesomeone2010/09/06 08:53 AM
                Why SOIDavid Kanter2010/09/06 05:19 PM
              Bulldozer article onlineJack2010/09/07 10:16 PM
                Bulldozer article onlineslacker2010/09/08 08:05 AM
                  Bulldozer article onlinesomeone2010/09/08 09:35 AM
                  Bulldozer article onlineJack2010/09/12 08:26 PM
                Bulldozer article onlinesomeone2010/09/08 09:03 AM
                  Some strawmen will never die (NT)slacker2010/09/08 09:13 AM
                    Yeah, like PD-SOI is worth the effort (NT)someone2010/09/08 09:39 AM
                      PDSOI is worth production dollars; FDSOI & silicon lasing are Intel's wet dreamslacker2010/09/08 10:54 AM
                  Bulldozer article onlineFritz2010/09/22 03:41 AM
                    Bulldozer article onlineanonymous2010/09/22 11:12 AM
                      Bulldozer article onlinesavantu2010/09/22 09:13 PM
      Bulldozer article onlineIan Ollmann2010/09/24 05:50 PM
        Bulldozer article onlineIan Ollmann2010/09/24 06:21 PM
          Bulldozer article onlineEduardoS2010/09/24 08:47 PM
            Bulldozer article onlineMichael S2010/09/25 10:41 AM
            Faster FADDPaul A. Clayton2010/09/25 11:58 AM
              Faster FADDEduardoS2010/09/25 12:07 PM
                Faster FADDPaul A. Clayton2010/09/28 11:29 AM
          Bulldozer article onlineMichael S2010/09/25 10:38 AM
        Bulldozer article onlineDavid Kanter2010/09/25 01:55 AM
        Bulldozer article onlineHans de Vries2010/09/26 06:58 AM
          Bulldozer article onlineDavid Kanter2010/09/26 10:38 AM
            Bulldozer article onlineHans de Vries2010/09/26 02:48 PM
              Bulldozer article onlineEduardoS2010/09/26 03:47 PM
                FP ADDs are not that fastMatt Waldhauer2010/09/30 07:46 AM
                  FP ADDs are not that fastsJ2010/09/30 11:24 AM
                    FP ADDs are not that fastEduardoS2010/09/30 01:41 PM
                      FP ADDs are not that fastrwessel2010/09/30 02:41 PM
                    FP ADDs are not that fastHans de Vries2010/09/30 07:11 PM
                  FP ADDs are not that fastEduardoS2010/09/30 01:43 PM
                    FP ADDs are not that fastMichael S2010/09/30 02:25 PM
                      FP ADDs are not that fastEduardoS2010/09/30 02:57 PM
                      FP ADDs are not that fastEric Quinnell2010/10/01 01:29 PM
                        FP ADDs are not that fastEduardoS2010/10/01 01:40 PM
                          FP ADDs are not that fastDavid Kanter2010/10/01 02:29 PM
                        Delayed post-result shift?Paul A. Clayton2010/10/01 06:14 PM
              Bulldozer article onlineDavid Kanter2010/09/26 03:50 PM
                Fusing into FMAPaul A. Clayton2010/09/27 02:01 PM
                  Fusing into FMAIan Ollmann2010/09/28 04:58 PM
                    Fusing into FMAPaul A. Clayton2010/09/29 07:25 AM
              Bulldozer article onlineMichael S2010/09/26 04:23 PM
                Bulldozer article onlineanonymous2010/09/27 01:38 AM
                  Bulldozer article onlineMichael S2010/09/27 05:00 AM
          Bulldozer article onlineEduardoS2010/09/26 10:51 AM
            Bulldozer article onlineHans de Vries2010/09/26 12:32 PM
          Bulldozer article onlineHans de Vries2010/09/26 12:28 PM
  Bulldozer article onlineMS2010/09/01 06:15 AM
  10h family 4MiB page TLB entriesPaul A. Clayton2010/09/01 06:01 PM
    10h family 4MiB page TLB entriesEduardoS2010/09/01 06:40 PM
      10h family 4MiB page TLB entriesrwessel2010/09/02 04:09 AM
        10h family 4MiB page TLB entriesEduardoS2010/09/02 03:04 PM
  Bulldozer article onlineDan Downs2010/09/02 08:28 AM
    Bulldozer article onlineslacker2010/09/02 08:37 AM
      Bulldozer article onlineDan Downs2010/09/02 10:06 AM
        Bulldozer article onlineDavid Kanter2010/09/02 04:41 PM
          Bulldozer article onlineDan Downs2010/09/02 10:42 PM
    one thread in two cores - NOHeikki Kultala2010/09/02 10:25 PM
      RF portsDavid Kanter2010/09/04 01:32 PM
  Slightly OT, but does iAtom use physical register files (PRF), too ? (NT)Alex2010/09/02 03:49 PM
    AFAIK Atom does not rename registersHeikki Kultala2010/09/03 03:46 AM
      AFAIK Atom does not rename registersAlex2010/09/03 08:41 AM
  FMACs can be ganged together, confirmed already by JF (link inside)Alex2010/09/08 04:44 PM
    FMACs can be ganged together, confirmed already by JF (link inside)David Kanter2010/09/09 07:32 AM
      FMACs can be ganged together, confirmed already by JF (link inside)Triskaine2010/09/09 07:48 AM
        FMACs can be ganged together, confirmed already by JF (link inside)David Kanter2010/09/09 08:11 AM
          FMACs can be ganged together, confirmed already by JF (link inside)arb2010/09/09 09:22 AM
            Bulldozer and AVXDavid Kanter2010/09/09 10:21 AM
          FMACs can be ganged together, confirmed already by JF (link inside)gruehunter2010/09/09 01:08 PM
            FMACs can be ganged together, confirmed already by JF (link inside)David Kanter2010/09/09 04:39 PM
              FMACs can be ganged together, confirmed already by JF (link inside)redpriest2010/09/09 09:56 PM
                FMACs can be ganged together, confirmed already by JF (link inside)Anthony2010/09/10 11:59 AM
                  FMACs can be ganged together, confirmed already by JF (link inside)someone2010/09/10 12:11 PM
      FMACs can be ganged together, confirmed already by JF (link inside)Alex2010/09/10 12:04 PM
    FMACs can be ganged together, confirmed already by JF (link inside) -- Oh No JFFritz2010/09/22 04:37 AM
      FMACs can be ganged together, confirmed already by JF (link inside) -- Oh No JFAnthony2010/09/22 11:01 AM
        FMACs can be ganged together, confirmed already by JF (link inside) -- Oh No JFDavid Kanter2010/09/22 11:22 AM
          FMACs can be ganged together, confirmed already by JF (link inside) -- Oh No JFanon2010/09/22 12:19 PM
            Bulldozer FPDavid Kanter2010/09/22 03:32 PM
              Bulldozer FPEduardoS2010/09/22 04:17 PM
                Bulldozer FPAaron Spink2010/09/23 12:13 PM
                  Bulldozer FPEduardoS2010/09/23 02:04 PM
                Bulldozer FPMichael S2010/09/23 01:26 PM
              Bulldozer FPanonymous2010/09/22 04:35 PM
              Bulldozer FPhobold2010/09/23 08:21 AM
                Bulldozer FPanon2010/09/23 11:59 AM
                  Bulldozer FPEduardoS2010/09/23 02:12 PM
                  Bulldozer FPhobold2010/09/23 02:19 PM
              Bulldozer FPHans de Vries2010/09/23 10:07 AM
                Bulldozer FPEric Bron2010/09/23 11:05 AM
          FMACs can be ganged together, confirmed already by JF (link inside) -- Oh No JFredpriest2010/09/23 05:47 PM
      FMACs can be ganged together, confirmed already by JF (link inside) -- Oh No JFAnthony2010/09/22 11:01 AM
  Bulldozer article onlineMarcal2010/09/29 03:13 AM
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