In defense of Bulldozer's Oddities

By: David Kanter (dkanter.delete@this.realworldtech.com), April 28, 2012 6:29 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.04/19/12 03:05 AM
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    Single page view?wainwright04/19/12 09:22 AM
    Single page view?slothrop04/19/12 09:23 AM
      Single page view?David Kanter04/19/12 09:31 AM
        Single page view?EduardoS04/19/12 03:12 PM
    Is there a single page view option for RWT articles?anon04/19/12 09:27 AM
    Single page view?Del04/19/12 09:36 AM
      Single page view?slacker04/19/12 03:56 PM
        Single page view?Del04/22/12 06:09 AM
          Single page view?David Kanter04/22/12 09:38 AM
            Single page view?Del04/23/12 01:22 AM
    Single page view?Michael S04/19/12 01:30 PM
      Single page view?Ungo04/19/12 02:25 PM
        Single page view?Foo_04/20/12 12:17 AM
          Single page view?James04/20/12 04:01 AM
            There are ads on the web?JJB04/20/12 04:32 AM
              What a bunch of freeloaders (NT)slacker04/20/12 01:44 PM
                So are you, probablyiz04/21/12 04:41 AM
                  Impression ad revenuePaul A. Clayton04/21/12 06:44 AM
                  So are you, probablyslacker04/21/12 01:09 PM
                    So are you, probablyDavid Kanter04/22/12 09:41 AM
                      So are you, probablyiz04/22/12 03:57 PM
                    So are you, probablyDoug Siebert04/22/12 12:37 PM
                      Aha!David Kanter04/22/12 03:45 PM
                        Aha!bakaneko04/22/12 08:49 PM
                    So are you, probablyiz04/22/12 03:48 PM
                      That's not how the business works...David Kanter04/22/12 05:31 PM
                        That's not how the business works...iz04/23/12 01:49 AM
                      So are you, probablyslacker04/22/12 11:31 PM
                        back to phoronixMichael S04/23/12 02:07 AM
                        So are you, probablyiz04/23/12 03:29 AM
                          Membership at RWTDavid Kanter04/23/12 11:24 AM
                          So are you, probablyJukka Larja04/27/12 08:59 AM
  So, what do people think of these numbers>I.S.T.04/19/12 07:34 PM
    So, what do people think of these numbers>Linus Torvalds04/20/12 08:34 AM
      So, what do people think of these numbers>Kira04/20/12 09:18 AM
        So, what do people think of these numbers>Linus Torvalds04/20/12 10:05 AM
      So, what do people think of these numbers>Doug Siebert04/20/12 09:00 PM
      So, what do people think of these numbers>Megol04/21/12 09:05 AM
        So, what do people think of these numbers>Linus Torvalds04/21/12 01:11 PM
          Most problems are fixed...Megol04/24/12 07:00 AM
    So, what do people think of these numbers>bakaneko04/20/12 11:16 AM
      So, what do people think of these numbers>bakaneko04/20/12 11:37 AM
        So, what do people think of these numbers>Linus Torvalds04/20/12 01:24 PM
          So, what do people think of these numbers>Joel04/20/12 02:59 PM
            So, what do people think of these numbers>Kira04/20/12 03:32 PM
              So, what do people think of these numbers>EduardoS04/20/12 04:00 PM
                Bulldozer's Oddities.Joel04/20/12 04:54 PM
                  In defense of Bulldozer's OdditiesDavid Kanter04/20/12 05:32 PM
                    In defense of Bulldozer's OdditiesExophase04/20/12 07:11 PM
                      In defense of Bulldozer's OdditiesEduardoS04/20/12 07:46 PM
                        In defense of Bulldozer's OdditiesExophase04/20/12 08:18 PM
                          In defense of Bulldozer's Odditiesanonymous04/20/12 11:26 PM
                            In defense of Bulldozer's OdditiesJJB04/20/12 11:34 PM
                              In defense of Bulldozer's Odditiesimaxx04/21/12 07:21 AM
                                In defense of Bulldozer's OdditiesMichael S04/21/12 10:42 AM
                                  Bulldozer's integer execution unitsDavid Kanter04/25/12 04:29 PM
                                    Bulldozer's integer execution unitsExophase04/26/12 12:17 PM
                                      Bulldozer's integer execution unitsanonymous04/26/12 03:15 PM
                                        Bulldozer's integer execution unitsEduardoS04/26/12 03:40 PM
                                          Bulldozer's integer execution unitsFoo_04/27/12 08:21 AM
                                            Bulldozer's integer execution unitsMegol04/27/12 01:38 PM
                                      Bulldozer's integer execution unitsEduardoS04/26/12 03:47 PM
                                        Bulldozer's integer execution unitsExophase04/26/12 05:02 PM
                                          Bulldozer's integer execution unitsEduardoS04/26/12 06:03 PM
                                            Bulldozer's integer execution unitsExophase04/26/12 06:24 PM
                                              Bulldozer's integer execution unitsEduardoS04/26/12 07:18 PM
                                                Bulldozer's cache memory performanceHeikki Kultala04/28/12 01:18 AM
                                                  Bulldozer's cache memory performanceEduardoS04/28/12 10:06 AM
                                      Bulldozer's integer execution unitsDavid Kanter04/26/12 04:03 PM
                                        Bulldozer's integer execution unitsExophase04/26/12 04:59 PM
                                          Bulldozer's integer execution unitsDavid Kanter04/26/12 10:53 PM
                                            Bulldozer's integer execution unitsExophase04/27/12 08:42 AM
                                              Bulldozer's integer execution unitsDavid Kanter04/27/12 11:06 AM
                                                Bulldozer's integer execution unitsEduardoS04/27/12 01:27 PM
                                                K8 divided pipelines?Paul A. Clayton04/27/12 01:59 PM
                                          Bulldozer's integer execution unitsMichael S04/27/12 04:37 AM
                                            Bulldozer's integer execution unitsExophase04/27/12 08:33 AM
                                            Bulldozer's integer execution unitsanonymous04/27/12 09:03 AM
                                    Renaming FlagsKonrad Schwarz04/27/12 03:04 AM
                                      Renaming Flagsnone04/27/12 04:03 AM
                                        Renaming FlagsMegol04/27/12 12:42 PM
                                    Bulldozer's integer execution unitshcl6404/27/12 04:31 PM
                                      VEX supports 3+ operands. FPU have renaming already(NT)Megol04/28/12 08:20 AM
                              In defense of Bulldozer's OdditiesLinus Torvalds04/21/12 12:26 PM
                                Thanks for the lessonJJB04/21/12 02:23 PM
                                  Side note..Linus Torvalds04/21/12 02:57 PM
                            In defense of Bulldozer's OdditiesExophase04/21/12 12:13 PM
                            In defense of Bulldozer's OdditiesEduardoS04/21/12 12:53 PM
                    In defense of Bulldozer's OdditiesGionatan Danti04/21/12 12:42 PM
                    In defense of Bulldozer's Odditieshcl6404/27/12 05:07 PM
                      In defense of Bulldozer's OdditiesDavid Kanter04/28/12 06:29 AM
                        In defense of Bulldozer's Odditieshcl6404/28/12 02:44 PM
                          In defense of Bulldozer's OdditiesDavid Kanter04/28/12 09:42 PM
                            In defense of Bulldozer's Odditieshcl6404/28/12 10:39 PM
                  Bulldozer's Oddities.EduardoS04/20/12 06:05 PM
                    Bulldozer's Oddities.anon04/20/12 08:32 PM
                      Bulldozer's Oddities.EduardoS04/21/12 12:37 PM
                        Bulldozer's Oddities.anon04/21/12 10:16 PM
                          Bulldozer's Oddities.EduardoS04/21/12 10:43 PM
                            Bulldozer's Oddities.anon04/22/12 02:09 AM
                              Bulldozer's Oddities.EduardoS04/22/12 01:57 PM
                                Bulldozer's Oddities.anon04/22/12 04:17 PM
                                  Bulldozer's Oddities.EduardoS04/22/12 05:05 PM
                                    Bulldozer's Oddities.anon04/22/12 05:42 PM
                                      Bulldozer's Oddities.anon04/22/12 06:01 PM
                                      Bulldozer's Oddities.EduardoS04/22/12 10:28 PM
                                        Bulldozer's Oddities.anon04/22/12 11:05 PM
                  Bulldozer's isn't bad.a reader04/21/12 10:01 AM
                    Bulldozer's isn't bad.Kira04/21/12 11:29 AM
                      Bulldozer's isn't bad.hcl6404/27/12 05:58 PM
                        Bulldozer's isn't bad.anon04/27/12 06:16 PM
                          Bulldozer's isn't bad.hcl6404/27/12 07:33 PM
                            Bulldozer's isn't bad.rwessel04/27/12 11:12 PM
                        Bulldozer's isn't bad.EduardoS04/28/12 09:29 AM
                          Bulldozer's isn't bad.EduardoS04/28/12 09:30 AM
                          Bulldozer's isn't bad.Michael S04/28/12 12:36 PM
                    Bulldozer is made for SPEC fpPelle-4804/21/12 11:41 AM
                  Bulldozer's Oddities.mpx04/22/12 03:47 AM
                    Bulldozer's Oddities.EduardoS04/22/12 01:57 PM
                      Bulldozer's Oddities.mpx04/23/12 07:04 AM
                        Bulldozer's Oddities.Eric04/23/12 12:33 PM
                          Bulldozer's Oddities.EduardoS04/23/12 02:22 PM
                            Bulldozer's Oddities.Eric04/23/12 07:30 PM
                              Bulldozer's Oddities.hcl6404/27/12 06:16 PM
                            Bulldozer's Oddities.Y04/25/12 04:34 AM
                              Bulldozer's IDIVHeikki Kultala04/27/12 10:56 PM
                                Bulldozer's IDIVY04/30/12 01:51 AM
                                  Bulldozer's IDIVEduardoS04/30/12 05:39 AM
                                    Bulldozer's IDIVP3Dnow05/08/12 01:23 AM
                                      Bulldozer's IDIVExophase05/08/12 07:37 AM
                        Bulldozer's Oddities.EduardoS04/23/12 02:15 PM
              Clustered MT as SMT for high frequencyPaul A. Clayton04/20/12 04:10 PM
                Clustered MT as SMT for high frequencyhcl6404/28/12 12:56 AM
                  Clustered MT as SMT for high frequencyanonymous04/28/12 01:43 AM
                    Clustered MT as SMT for high frequencyhcl6404/28/12 02:59 PM
                      Clustered MT as SMT for high frequencyanonymous04/28/12 08:45 PM
                  Clustered MT as SMT for high frequencyanon04/28/12 02:13 AM
                    Clustered MT as SMT for high frequencyhcl6404/28/12 03:23 PM
                      Clustered MT as SMT for high frequencyanon04/28/12 06:19 PM
                        Clustered MT as SMT for high frequencyhcl6404/28/12 07:58 PM
                  Clustered MT as SMT for high frequencyDavid Kanter04/28/12 06:38 AM
                    Guessed meaning of "strong dependency model"Paul A. Clayton04/28/12 07:24 AM
                      Guessed meaning of "strong dependency model"EduardoS04/28/12 09:46 AM
                        *Right meaning* about "strong dependency model"hcl6404/28/12 04:59 PM
                    Clustered MT as SMT for high frequencyhcl6404/28/12 04:24 PM
                      Clustered MT as SMT for high frequencyanonymous04/28/12 08:50 PM
                        Clustered MT as SMT for high frequencyhcl6404/28/12 09:47 PM
                          SNB widthDavid Kanter04/28/12 09:48 PM
                            SNB widthhcl6404/29/12 02:24 AM
                      Clustered MT as SMT for high frequencyDavid Kanter04/28/12 09:56 PM
                        Clustered MT as SMT for high frequencyhcl6404/28/12 11:44 PM
                          SOI, FD vs. PDDavid Kanter04/29/12 07:19 AM
                            SOI, FD vs. PDhcl6404/29/12 05:31 PM
                              SOI, FD vs. PDDavid Kanter04/29/12 11:26 PM
                                SOI, FD vs. PDhcl6404/30/12 08:08 AM
                                  SOI, FD vs. PDDavid Kanter04/30/12 09:59 AM
                                    SOI, FD vs. PDhcl6404/30/12 06:10 PM
                                      SOI, FD vs. PDDavid Kanter04/30/12 06:32 PM
                                        SOI, FD vs. PDhcl6404/30/12 10:47 PM
                                          SOI, FD vs. PDDavid Kanter05/01/12 02:24 AM
                                            SOI, FD vs. PDhcl6405/01/12 05:46 AM
                                            SOI, FD vs. PDhcl6405/01/12 06:37 AM
                                              SOI, FD vs. PDDavid Kanter05/01/12 08:19 AM
                                          SOI, FD vs. PDhcl6405/01/12 07:39 AM
                                            PD-SOIDavid Kanter05/02/12 12:22 PM
                                    SOI, FD vs. PDslacker04/30/12 08:10 PM
                                      SOI, FD vs. PDDavid Kanter04/30/12 10:16 PM
                                        SOI, FD vs. PDslacker05/01/12 10:04 PM
                                          SOI, FD vs. PDDavid Kanter05/02/12 08:19 AM
                                            SOI, FD vs. PDzou05/02/12 12:23 PM
                  Previous discussion of clustered MTPaul A. Clayton04/28/12 07:00 AM
                    Previous discussion of clustered MThcl6404/28/12 09:38 PM
                      Previous discussion of clustered MTDavid Kanter04/30/12 04:37 PM
                        Previous discussion of clustered MThcl6404/30/12 07:24 PM
                          Previous discussion of clustered MTDavid Kanter04/30/12 07:40 PM
                            Previous discussion of clustered MThcl6405/01/12 09:15 AM
                              Latency issuesDavid Kanter05/02/12 12:01 PM
              So, what do people think of these numbers>Megol04/21/12 01:57 AM
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