In defense of Bulldozer's Oddities

By: David Kanter (dkanter.delete@this.realworldtech.com), April 28, 2012 5:29 am
Room: Moderated Discussions
hcl64 (mario.smarq@gmail.com) on 4/27/12 wrote:
---------------------------
>David Kanter (dkanter@realworldtech.com) on 4/20/12 wrote:
>---------------------------
>>
>>You are correct that the caches are painfully slow, but that's not the reason why.
>>Frankly, I don't understand why the L1 is 4 cycles instead of 3. I REALLY don't
>>understand why the L2 cache is so slow (20 cycles, really??), because size alone
>>doesn't account for it. 12-14 cycles sounds much more reasonable.
>>
>>The L3 cache is also quite slow, in part because of the slow L2 and in part because
>>it runs at asynchronous to the cores. If you look at those two factors together
>>and assume a 14 cycle L2, you can probably cut the L3 latency down by ~10 cycles.
>>
>>
>>DK

>Good points. But isn't BD mostly asynchronous or semi->synchronous ?

No. You should read my article about Bulldozer.

http://www.realworldtech.com/page.cfm?ArticleID=RWT082610181333

Decoupled and asynchronous mean very different things. Asynchronous refers to frequency. Decoupled means there are buffers between stages. Those are two very different concepts and have very different implications for design.

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