Bulldozer's Oddities.

By: EduardoS (no.delete@this.spam.com), April 20, 2012 6:05 pm
Room: Moderated Discussions
Joel (joel.hruska@gmail.com) on 4/20/12 wrote:
---------------------------
>Both my own tests and those done elsewhere have indicated that sharing the front-end
>as it does "cost" Bulldozer between 10-20% of its theoretical performance. In and
>of itself, that's not bad -- compared to Thuban, they saved more than 10-20% die space (assuming all else equal).

Bulldozer front-end is much bigger than that of Thuban, a front-end that big wouldn't be possible without being shared to begin with, the comparison is irrelevant.

>The problem is, all else *isn't* equal. AMD stuffed Bulldozer with cache (an eight-core
>BD has something like 16MB of cache compared to 10MB of cache for a 6-core Thuban).

And I have another data for you, space on logic eats much more power than space on caches, for server CPUs caches are a lot power efficient, on desktop/mobile they can be omited, like in the case of Trinity.

>That blows the die-size savings apart...which might still be ok, if the caches were
>fast. They aren't. In fact, they're painfully slow. Because every L1 write is duplicated
>in L2, L1 write latency is effectively pinned to L2 write latency.
>
>I still believe BD's biggest problem is its cache latencies, but the chip as it
>shipped last year is a badly flawed piece of work.

Hell... The only task Bulldozer does reasonable well is memory intensive taks, Agner have write a document saying BD memory subsystem is ok and people still point at it? What is needed for people to look elsewhere? Why nobody look at the 2-wide integer unit? The small instruction window? Always cahce latency... why not looking at cache bandwidth? Why not looking at anything else? Memory subsystem is ok, frankly, maybe the only part that is ok...

L1 load latency is 4 cycles, like Nehalem and Sandy Bridge but BD hits a much higher frequency, L1 store queue have 24 entries, more than enough to hide L2 20 cycles latency, the L2 itself, at BD target frequency 20 cycles is no more latency than other designs with same size, all left is L3 latency, for the role it takes it is not a problem.
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Phoronix tests GCC compiler flags and Bulldozer.I.S.T.2012/04/19 03:05 AM
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        Single page view?Del2012/04/22 06:09 AM
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            Single page view?Del2012/04/23 01:22 AM
    Single page view?Michael S2012/04/19 01:30 PM
      Single page view?Ungo2012/04/19 02:25 PM
        Single page view?Foo_2012/04/20 12:17 AM
          Single page view?James2012/04/20 04:01 AM
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              What a bunch of freeloaders (NT)slacker2012/04/20 01:44 PM
                So are you, probablyiz2012/04/21 04:41 AM
                  Impression ad revenuePaul A. Clayton2012/04/21 06:44 AM
                  So are you, probablyslacker2012/04/21 01:09 PM
                    So are you, probablyDavid Kanter2012/04/22 09:41 AM
                      So are you, probablyiz2012/04/22 03:57 PM
                    So are you, probablyDoug Siebert2012/04/22 12:37 PM
                      Aha!David Kanter2012/04/22 03:45 PM
                        Aha!bakaneko2012/04/22 08:49 PM
                    So are you, probablyiz2012/04/22 03:48 PM
                      That's not how the business works...David Kanter2012/04/22 05:31 PM
                        That's not how the business works...iz2012/04/23 01:49 AM
                      So are you, probablyslacker2012/04/22 11:31 PM
                        back to phoronixMichael S2012/04/23 02:07 AM
                        So are you, probablyiz2012/04/23 03:29 AM
                          Membership at RWTDavid Kanter2012/04/23 11:24 AM
                          So are you, probablyJukka Larja2012/04/27 08:59 AM
  So, what do people think of these numbers>I.S.T.2012/04/19 07:34 PM
    So, what do people think of these numbers>Linus Torvalds2012/04/20 08:34 AM
      So, what do people think of these numbers>Kira2012/04/20 09:18 AM
        So, what do people think of these numbers>Linus Torvalds2012/04/20 10:05 AM
      So, what do people think of these numbers>Doug Siebert2012/04/20 09:00 PM
      So, what do people think of these numbers>Megol2012/04/21 09:05 AM
        So, what do people think of these numbers>Linus Torvalds2012/04/21 01:11 PM
          Most problems are fixed...Megol2012/04/24 07:00 AM
    So, what do people think of these numbers>bakaneko2012/04/20 11:16 AM
      So, what do people think of these numbers>bakaneko2012/04/20 11:37 AM
        So, what do people think of these numbers>Linus Torvalds2012/04/20 01:24 PM
          So, what do people think of these numbers>Joel2012/04/20 02:59 PM
            So, what do people think of these numbers>Kira2012/04/20 03:32 PM
              So, what do people think of these numbers>EduardoS2012/04/20 04:00 PM
                Bulldozer's Oddities.Joel2012/04/20 04:54 PM
                  In defense of Bulldozer's OdditiesDavid Kanter2012/04/20 05:32 PM
                    In defense of Bulldozer's OdditiesExophase2012/04/20 07:11 PM
                      In defense of Bulldozer's OdditiesEduardoS2012/04/20 07:46 PM
                        In defense of Bulldozer's OdditiesExophase2012/04/20 08:18 PM
                          In defense of Bulldozer's Odditiesanonymous2012/04/20 11:26 PM
                            In defense of Bulldozer's OdditiesJJB2012/04/20 11:34 PM
                              In defense of Bulldozer's Odditiesimaxx2012/04/21 07:21 AM
                                In defense of Bulldozer's OdditiesMichael S2012/04/21 10:42 AM
                                  Bulldozer's integer execution unitsDavid Kanter2012/04/25 04:29 PM
                                    Bulldozer's integer execution unitsExophase2012/04/26 12:17 PM
                                      Bulldozer's integer execution unitsanonymous2012/04/26 03:15 PM
                                        Bulldozer's integer execution unitsEduardoS2012/04/26 03:40 PM
                                          Bulldozer's integer execution unitsFoo_2012/04/27 08:21 AM
                                            Bulldozer's integer execution unitsMegol2012/04/27 01:38 PM
                                      Bulldozer's integer execution unitsEduardoS2012/04/26 03:47 PM
                                        Bulldozer's integer execution unitsExophase2012/04/26 05:02 PM
                                          Bulldozer's integer execution unitsEduardoS2012/04/26 06:03 PM
                                            Bulldozer's integer execution unitsExophase2012/04/26 06:24 PM
                                              Bulldozer's integer execution unitsEduardoS2012/04/26 07:18 PM
                                                Bulldozer's cache memory performanceHeikki Kultala2012/04/28 01:18 AM
                                                  Bulldozer's cache memory performanceEduardoS2012/04/28 10:06 AM
                                      Bulldozer's integer execution unitsDavid Kanter2012/04/26 04:03 PM
                                        Bulldozer's integer execution unitsExophase2012/04/26 04:59 PM
                                          Bulldozer's integer execution unitsDavid Kanter2012/04/26 10:53 PM
                                            Bulldozer's integer execution unitsExophase2012/04/27 08:42 AM
                                              Bulldozer's integer execution unitsDavid Kanter2012/04/27 11:06 AM
                                                Bulldozer's integer execution unitsEduardoS2012/04/27 01:27 PM
                                                K8 divided pipelines?Paul A. Clayton2012/04/27 01:59 PM
                                          Bulldozer's integer execution unitsMichael S2012/04/27 04:37 AM
                                            Bulldozer's integer execution unitsExophase2012/04/27 08:33 AM
                                            Bulldozer's integer execution unitsanonymous2012/04/27 09:03 AM
                                    Renaming FlagsKonrad Schwarz2012/04/27 03:04 AM
                                      Renaming Flagsnone2012/04/27 04:03 AM
                                        Renaming FlagsMegol2012/04/27 12:42 PM
                                    Bulldozer's integer execution unitshcl642012/04/27 04:31 PM
                                      VEX supports 3+ operands. FPU have renaming already(NT)Megol2012/04/28 08:20 AM
                              In defense of Bulldozer's OdditiesLinus Torvalds2012/04/21 12:26 PM
                                Thanks for the lessonJJB2012/04/21 02:23 PM
                                  Side note..Linus Torvalds2012/04/21 02:57 PM
                            In defense of Bulldozer's OdditiesExophase2012/04/21 12:13 PM
                            In defense of Bulldozer's OdditiesEduardoS2012/04/21 12:53 PM
                    In defense of Bulldozer's OdditiesGionatan Danti2012/04/21 12:42 PM
                    In defense of Bulldozer's Odditieshcl642012/04/27 05:07 PM
                      In defense of Bulldozer's OdditiesDavid Kanter2012/04/28 06:29 AM
                        In defense of Bulldozer's Odditieshcl642012/04/28 02:44 PM
                          In defense of Bulldozer's OdditiesDavid Kanter2012/04/28 09:42 PM
                            In defense of Bulldozer's Odditieshcl642012/04/28 10:39 PM
                  Bulldozer's Oddities.EduardoS2012/04/20 06:05 PM
                    Bulldozer's Oddities.anon2012/04/20 08:32 PM
                      Bulldozer's Oddities.EduardoS2012/04/21 12:37 PM
                        Bulldozer's Oddities.anon2012/04/21 10:16 PM
                          Bulldozer's Oddities.EduardoS2012/04/21 10:43 PM
                            Bulldozer's Oddities.anon2012/04/22 02:09 AM
                              Bulldozer's Oddities.EduardoS2012/04/22 01:57 PM
                                Bulldozer's Oddities.anon2012/04/22 04:17 PM
                                  Bulldozer's Oddities.EduardoS2012/04/22 05:05 PM
                                    Bulldozer's Oddities.anon2012/04/22 05:42 PM
                                      Bulldozer's Oddities.anon2012/04/22 06:01 PM
                                      Bulldozer's Oddities.EduardoS2012/04/22 10:28 PM
                                        Bulldozer's Oddities.anon2012/04/22 11:05 PM
                  Bulldozer's isn't bad.a reader2012/04/21 10:01 AM
                    Bulldozer's isn't bad.Kira2012/04/21 11:29 AM
                      Bulldozer's isn't bad.hcl642012/04/27 05:58 PM
                        Bulldozer's isn't bad.anon2012/04/27 06:16 PM
                          Bulldozer's isn't bad.hcl642012/04/27 07:33 PM
                            Bulldozer's isn't bad.rwessel2012/04/27 11:12 PM
                        Bulldozer's isn't bad.EduardoS2012/04/28 09:29 AM
                          Bulldozer's isn't bad.EduardoS2012/04/28 09:30 AM
                          Bulldozer's isn't bad.Michael S2012/04/28 12:36 PM
                    Bulldozer is made for SPEC fpPelle-482012/04/21 11:41 AM
                  Bulldozer's Oddities.mpx2012/04/22 03:47 AM
                    Bulldozer's Oddities.EduardoS2012/04/22 01:57 PM
                      Bulldozer's Oddities.mpx2012/04/23 07:04 AM
                        Bulldozer's Oddities.Eric2012/04/23 12:33 PM
                          Bulldozer's Oddities.EduardoS2012/04/23 02:22 PM
                            Bulldozer's Oddities.Eric2012/04/23 07:30 PM
                              Bulldozer's Oddities.hcl642012/04/27 06:16 PM
                            Bulldozer's Oddities.Y2012/04/25 04:34 AM
                              Bulldozer's IDIVHeikki Kultala2012/04/27 10:56 PM
                                Bulldozer's IDIVY2012/04/30 01:51 AM
                                  Bulldozer's IDIVEduardoS2012/04/30 05:39 AM
                                    Bulldozer's IDIVP3Dnow2012/05/08 01:23 AM
                                      Bulldozer's IDIVExophase2012/05/08 07:37 AM
                        Bulldozer's Oddities.EduardoS2012/04/23 02:15 PM
              Clustered MT as SMT for high frequencyPaul A. Clayton2012/04/20 04:10 PM
                Clustered MT as SMT for high frequencyhcl642012/04/28 12:56 AM
                  Clustered MT as SMT for high frequencyanonymous2012/04/28 01:43 AM
                    Clustered MT as SMT for high frequencyhcl642012/04/28 02:59 PM
                      Clustered MT as SMT for high frequencyanonymous2012/04/28 08:45 PM
                  Clustered MT as SMT for high frequencyanon2012/04/28 02:13 AM
                    Clustered MT as SMT for high frequencyhcl642012/04/28 03:23 PM
                      Clustered MT as SMT for high frequencyanon2012/04/28 06:19 PM
                        Clustered MT as SMT for high frequencyhcl642012/04/28 07:58 PM
                  Clustered MT as SMT for high frequencyDavid Kanter2012/04/28 06:38 AM
                    Guessed meaning of "strong dependency model"Paul A. Clayton2012/04/28 07:24 AM
                      Guessed meaning of "strong dependency model"EduardoS2012/04/28 09:46 AM
                        *Right meaning* about "strong dependency model"hcl642012/04/28 04:59 PM
                    Clustered MT as SMT for high frequencyhcl642012/04/28 04:24 PM
                      Clustered MT as SMT for high frequencyanonymous2012/04/28 08:50 PM
                        Clustered MT as SMT for high frequencyhcl642012/04/28 09:47 PM
                          SNB widthDavid Kanter2012/04/28 09:48 PM
                            SNB widthhcl642012/04/29 02:24 AM
                      Clustered MT as SMT for high frequencyDavid Kanter2012/04/28 09:56 PM
                        Clustered MT as SMT for high frequencyhcl642012/04/28 11:44 PM
                          SOI, FD vs. PDDavid Kanter2012/04/29 07:19 AM
                            SOI, FD vs. PDhcl642012/04/29 05:31 PM
                              SOI, FD vs. PDDavid Kanter2012/04/29 11:26 PM
                                SOI, FD vs. PDhcl642012/04/30 08:08 AM
                                  SOI, FD vs. PDDavid Kanter2012/04/30 09:59 AM
                                    SOI, FD vs. PDhcl642012/04/30 06:10 PM
                                      SOI, FD vs. PDDavid Kanter2012/04/30 06:32 PM
                                        SOI, FD vs. PDhcl642012/04/30 10:47 PM
                                          SOI, FD vs. PDDavid Kanter2012/05/01 02:24 AM
                                            SOI, FD vs. PDhcl642012/05/01 05:46 AM
                                            SOI, FD vs. PDhcl642012/05/01 06:37 AM
                                              SOI, FD vs. PDDavid Kanter2012/05/01 08:19 AM
                                          SOI, FD vs. PDhcl642012/05/01 07:39 AM
                                            PD-SOIDavid Kanter2012/05/02 12:22 PM
                                    SOI, FD vs. PDslacker2012/04/30 08:10 PM
                                      SOI, FD vs. PDDavid Kanter2012/04/30 10:16 PM
                                        SOI, FD vs. PDslacker2012/05/01 10:04 PM
                                          SOI, FD vs. PDDavid Kanter2012/05/02 08:19 AM
                                            SOI, FD vs. PDzou2012/05/02 12:23 PM
                  Previous discussion of clustered MTPaul A. Clayton2012/04/28 07:00 AM
                    Previous discussion of clustered MThcl642012/04/28 09:38 PM
                      Previous discussion of clustered MTDavid Kanter2012/04/30 04:37 PM
                        Previous discussion of clustered MThcl642012/04/30 07:24 PM
                          Previous discussion of clustered MTDavid Kanter2012/04/30 07:40 PM
                            Previous discussion of clustered MThcl642012/05/01 09:15 AM
                              Latency issuesDavid Kanter2012/05/02 12:01 PM
              So, what do people think of these numbers>Megol2012/04/21 01:57 AM
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