ISSCC Poulson Preview Online - OoO not unlikely?

Article: New Itanium Microarchitecture at ISSCC 2011
By: ajensen (.delete@this..), November 18, 2010 12:48 am
Room: Moderated Discussions
anon (anon@anon.com) on 11/17/10 wrote:
---------------------------

>Avoiding OoO probably made a lot more sense 10 years ago than it does now.

Depends on what you mean by OoO and if more can be less..

Nehalem has 36 reservation stations to populate a 4 wide pipeline and a state of the art cache hierarchy. Poulson will probably have a better cache hierarchy with more parallelism, but latencies will be similar at least form L2 and so how many reservation stations would it require to populate a 12 wide pipeline? Perhaps (12/4)x36=108 is a reasonable assumption? And then there is some extra complexity added since Poulson will have far more execution units than Nehalem. The added complexity will be in the range of O(n²) to O(n³)... so about 500,000% to 40,000,000% more complex than Nehalem.

So if by OoO you mean plain old unrestricted Tomasulo engine? Well that is clearly not going to happen unless you want a chip the size of a football field. At least we could save some money on the clock generator by just pulling the 50Hz straight from the grid.

Traditional OoO has never made less sense IMO. We need to pursue methods where one has far less degrees of freedom. For IA64 the ILP is already visible to the CPU, what they need to fix is the unpredictable cache misses by making the CPU able to continue processing when a vanilla in-order CPU would stall. The simplest solution is to switch thread, and if you build a pipeline that tracks threads through the pipeline so that instructions form 2 or more threads can coexist in one stage then it should be rather simple to always have some work to do for most units.
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ISSCC Poulson Preview OnlineDavid Kanter2010/11/17 03:40 AM
  ISSCC Poulson Preview Onlinesavantu2010/11/17 05:25 AM
  ISSCC Poulson Preview Onlinesomeone2010/11/17 08:51 AM
    ISSCC Poulson Preview OnlineLinus Torvalds2010/11/17 09:27 AM
      ISSCC Poulson Preview Onlinesomeone2010/11/17 10:31 AM
        ISSCC Poulson Preview OnlineRichard Cownie2010/11/17 10:55 AM
          ISSCC Poulson Preview OnlineLinus Torvalds2010/11/17 11:30 AM
          ISSCC Poulson Preview Onlinesomeone2010/11/17 11:42 AM
            ISSCC Poulson Preview Onlinea reader2010/11/17 02:07 PM
        ISSCC Poulson Preview OnlineGabriele Svelto2010/11/19 02:52 AM
          ISSCC Poulson Preview Onlinesavantu2010/11/19 05:37 AM
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        ISSCC Poulson Preview OnlineDavid Kanter2010/11/17 02:08 PM
          ISSCC Poulson Preview Onlineajensen2010/11/18 01:24 AM
  ISSCC Poulson Preview Onlinelubemark2010/11/17 09:52 AM
  ISSCC Poulson Preview Online - OoO not unlikely?anon2010/11/17 11:41 AM
    ISSCC Poulson Preview Online - OoO not unlikely?Linus Torvalds2010/11/17 12:12 PM
      ISSCC Poulson Preview Online - OoO not unlikely?anon2010/11/17 05:38 PM
        ISSCC Poulson Preview Online - OoO not unlikely?Linus Torvalds2010/11/17 08:03 PM
    ISSCC Poulson Preview Online - OoO not unlikely?someone2010/11/17 12:14 PM
      ISSCC Poulson Preview Online - OoO not unlikely?Richard Cownie2010/11/17 02:07 PM
        ISSCC Poulson Preview Online - OoO not unlikely?someone2010/11/17 02:59 PM
          ISSCC Poulson Preview Online - OoO not unlikely?sylt2010/11/17 03:26 PM
          ISSCC Poulson Preview Online - OoO not unlikely?anon2010/11/17 05:53 PM
            ISSCC Poulson Preview Online - OoO not unlikely?someone2010/11/17 08:34 PM
              ISSCC Poulson Preview Online - OoO not unlikely?anon2010/11/17 09:22 PM
              ISSCC Poulson Preview Online - OoO not unlikely?Martin Høyer Kristiansen2010/11/18 12:35 AM
                ISSCC Poulson Preview Online - OoO not unlikely?anon2010/11/18 01:14 AM
                  ISSCC Poulson Preview Online - OoO not unlikely?Martin Høyer Kristiansen2010/11/18 02:00 AM
          ISSCC Poulson Preview Online - OoO not unlikely?Groo2010/11/18 03:28 PM
            ISSCC Poulson Preview Online - OoO not unlikely?someone2010/11/18 09:30 PM
              ISSCC Poulson Preview Online - OoO not unlikely?Doug Siebert2010/11/19 12:06 AM
                ISSCC Poulson Preview Online - OoO not unlikely?someone2010/11/19 07:52 AM
                  Negativity and ignorancePaul A. Clayton2010/11/19 06:11 PM
                  rhetoricshobold2010/11/20 05:01 AM
              ISSCC Poulson Preview Online - OoO not unlikely?anonymous2010/11/19 02:17 AM
                ISSCC Poulson Preview Online - OoO not unlikely?someone2010/11/19 08:22 AM
                  ISSCC Poulson Preview Online - OoO not unlikely?Linus Torvalds2010/11/19 09:26 AM
                    ISSCC Poulson Preview Online - OoO not unlikely?someone2010/11/19 11:04 AM
                      ISSCC Poulson Preview Online - OoO not unlikely?Linus Torvalds2010/11/19 11:24 AM
                        ISSCC Poulson Preview Online - OoO not unlikely?someone2010/11/19 12:05 PM
                          ISSCC Poulson Preview Online - OoO not unlikely?Linus Torvalds2010/11/19 01:08 PM
                            ISSCC Poulson Preview Online - OoO not unlikely?someone2010/11/20 11:02 AM
                              ISSCC Poulson Preview Online - OoO not unlikely?dc2010/11/20 12:59 PM
                              ISSCC Poulson Preview Online - OoO not unlikely?dc2010/11/20 01:01 PM
                                ISSCC Poulson Preview Online - OoO not unlikely?rwessel2010/11/20 01:27 PM
                                  ISSCC Poulson Preview Online - OoO not unlikely?dc2010/11/21 05:00 PM
                                    single-system single-location != RASanonymous2010/11/21 09:33 PM
                                      single-system single-location != RASdc2010/11/25 12:06 PM
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                        CS:SNAREPS. Rao2010/11/20 11:20 AM
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                  ISSCC Poulson Preview Online - OoO not unlikely?anon2010/11/19 11:08 AM
                    ISSCC Poulson Preview Online - OoO not unlikely?someone2010/11/19 06:51 PM
                      ISSCC Poulson Preview Online - OoO not unlikely?rwessel2010/11/20 01:53 AM
                        ISSCC Poulson Preview Online - OoO not unlikely?dc2010/11/20 12:43 PM
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                ISSCC Poulson Preview Online - OoO not unlikely?someone2010/11/21 10:24 AM
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                            ISSCC Poulson Preview Online - OoO not unlikely?someone2010/11/22 09:07 AM
                              ISSCC Poulson Preview Online - OoO not unlikely?Richard Cownie2010/11/22 09:25 AM
                                ISSCC Poulson Preview Online - OoO not unlikely?dc2010/11/25 12:22 PM
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