Separate the OoO-ness from speculative-ness

Article: PhysX87: Software Deficiency
By: anon (anon.delete@this.anon.com), July 21, 2010 4:53 pm
Room: Moderated Discussions
? (0xe2.0x9a.0x9b@gmail.com) on 7/21/10 wrote:
---------------------------
>anon (anon@anon.com) on 7/21/10 wrote:
>---------------------------
>>But you're wrong about this as an example of how pipelining requires speculation
>>because CPUs disallow such sequences without cache and pipeline draining instructions.
>
>There are two options of how to design a pipelined version of a CPU:
>
>1. Maintain full compatibility between the pipelined and non-pipelined versions,
>even for all the unlikely corner-cases such as intense self-modifying code. The
>two CPUs give mathematically identical results in all possible cases.
>
>2. Do not maintain full compatibility. One specimen of this approach are the transitions
>from 8086 to 286 to 386 to 486 etc.
>
>I was mainly talking about case (1).

snip

>>Exceptions are another one, but again it could have imprecise exceptions and not require speculative execution.
>
>Well, but you cannot go back to 1970 and fix 8086 so that it knows about the concept of imprecise exceptions.
>

snip

>>On the contrary, I think your assertion that pipelining requires speculative execution is wrong.
>
>I am not saying that. I am saying this: Pipelining, the way it is implemented in
>current CPUs (e.g: Core2), involves certain assumptions

I'm sorry, but you're just modifying your argument as you go along now. You can't tell me you were talking specifically about x86 and constraints of market realities in CPU design. Because we can all read what you posted to Linus.

"NOTE that this theoretical OoO CPU I am mentioning here
is *not* doing any *speculation* (except maybe those
which also present in the in-order CPU). Once you have
speculation, there by necessity exist some cases in which
the CPU's prediction engine will make a wrong decision.

Even mere pipelining entails a small dose of speculative
execution !!!

I will repeat it one more time, because it seems to me
that you are completely missing this: Even mere
pipelining entails a small dose of speculation !!!"

You are clearliy talking about theoretical designs, and you were saying that pipelining requires speculation.

snip

>>Caches have nothing to do with speculative execution that you were talking about.
>
>What are you saying? That if a contemporary CPU (Core2 or whatever) decides to
>allocate a cache-line for data at address 0x1230, it is not making any speculations
>about future uses of that piece of data?
>
>(Note: I am *not* against caches)
>

Yes there is a speculative nature about caches, of course it is nothing to do with speculative execution or anything in the CPU pipeline which is what this discussion was supposed to be about (out of order versus in order, pipelining, speculative execution etc). I'll quote you again

"Even mere pipelining entails a small dose of speculative
execution !!!"

I'm not saying you don't know the difference, but I'm saying that the argument about execution engines is only muddied by you bringing up caches.
< Previous Post in ThreadNext Post in Thread >
TopicPosted ByDate
A bit off baseJohn Mann2010/07/07 06:04 AM
  A bit off baseDavid Kanter2010/07/07 10:28 AM
    SSE vs x87Joel Hruska2010/07/07 11:53 AM
      SSE vs x87Michael S2010/07/07 12:07 PM
        SSE vs x87hobold2010/07/08 04:12 AM
      SSE vs x87David Kanter2010/07/07 01:55 PM
        SSE vs x87Andi Kleen2010/07/08 01:43 AM
          80 bit FPRicardo B2010/07/08 06:35 AM
            80 bit FPDavid Kanter2010/07/08 10:14 AM
              80 bit FPKevin G2010/07/08 01:12 PM
                80 bit FPIan Ollmann2010/07/18 11:49 PM
                  80 bit FPDavid Kanter2010/07/19 10:33 AM
                    80 bit FPAnil Maliyekkel2010/07/19 03:49 PM
                      80 bit FPrwessel2010/07/19 04:41 PM
                    80 bit FPMatt Waldhauer2010/07/21 10:11 AM
            80 bit FPEmil Briggs2010/07/22 08:06 AM
    A bit off baseJohn Mann2010/07/08 10:06 AM
      A bit off baseDavid Kanter2010/07/08 10:27 AM
        A bit off baseIan Ameline2010/07/09 09:10 AM
          A bit off baseMichael S2010/07/10 01:13 PM
            A bit off baseIan Ameline2010/07/11 06:51 AM
  A bit off baseDavid Kanter2010/07/07 08:46 PM
    A bit off baseAnon2010/07/07 11:47 PM
      A bit off baseanon2010/07/08 01:15 AM
        A bit off baseGabriele Svelto2010/07/08 03:11 AM
          Physics engine historyPeter Clare2010/07/08 03:49 AM
            Physics engine historyNull Pointer Exception2010/07/08 05:07 AM
              Physics engine historyRalf2010/07/08 02:09 PM
                Physics engine historyDavid Kanter2010/07/08 03:16 PM
                  Physics engine historysJ2010/07/08 10:36 PM
                    Physics engine historyGabriele Svelto2010/07/08 11:59 PM
                      Physics engine historysJ2010/07/13 05:35 AM
                    Physics engine historyDavid Kanter2010/07/09 08:25 AM
                      Physics engine historysJ2010/07/13 05:49 AM
                      Physics engine historyfvdbergh2010/07/13 06:27 AM
    A bit off baseJohn Mann2010/07/08 10:11 AM
      A bit off baseDavid Kanter2010/07/08 10:31 AM
        150 GFLOP/s measured?anon2010/07/08 06:10 PM
          150 GFLOP/s measured?David Kanter2010/07/08 06:53 PM
            150 GFLOP/s measured?Aaron Spink2010/07/08 08:05 PM
              150 GFLOP/s measured?anon2010/07/08 08:31 PM
                150 GFLOP/s measured?Aaron Spink2010/07/08 09:43 PM
                  150 GFLOP/s measured?David Kanter2010/07/08 10:27 PM
                    150 GFLOP/s measured?Ian Ollmann2010/07/19 12:14 AM
                      150 GFLOP/s measured?anon2010/07/19 05:39 AM
                        150 GFLOP/s measured?hobold2010/07/19 06:26 AM
                          Philosophy for achieving peakDavid Kanter2010/07/19 10:49 AM
                      150 GFLOP/s measured?Linus Torvalds2010/07/19 06:36 AM
                        150 GFLOP/s measured?Richard Cownie2010/07/19 07:42 AM
                          150 GFLOP/s measured?Aaron Spink2010/07/19 07:56 AM
                            150 GFLOP/s measured?hobold2010/07/19 08:30 AM
                              150 GFLOP/s measured?Groo2010/07/19 01:31 PM
                                150 GFLOP/s measured?hobold2010/07/19 03:17 PM
                                  150 GFLOP/s measured?Groo2010/07/19 05:18 PM
                              150 GFLOP/s measured?Anon2010/07/19 05:18 PM
                            150 GFLOP/s measured?Mark Roulo2010/07/19 10:47 AM
                              150 GFLOP/s measured?slacker2010/07/19 11:55 AM
                                150 GFLOP/s measured?Mark Roulo2010/07/19 12:00 PM
                              150 GFLOP/s measured?anonymous422010/07/25 11:31 AM
                            150 GFLOP/s measured?Richard Cownie2010/07/19 11:41 AM
                              150 GFLOP/s measured?Linus Torvalds2010/07/19 01:57 PM
                                150 GFLOP/s measured?Richard Cownie2010/07/19 03:10 PM
                                150 GFLOP/s measured?Richard Cownie2010/07/19 03:10 PM
                                  150 GFLOP/s measured?hobold2010/07/19 03:25 PM
                                  150 GFLOP/s measured?Linus Torvalds2010/07/19 03:31 PM
                                    150 GFLOP/s measured?Richard Cownie2010/07/20 05:04 AM
                                150 GFLOP/s measured?jrl2010/07/20 12:18 AM
                            150 GFLOP/s measured?anonymous422010/07/25 11:00 AM
                              150 GFLOP/s measured?David Kanter2010/07/25 11:52 AM
                          150 GFLOP/s measured?Anon2010/07/19 05:15 PM
                            150 GFLOP/s measured?Linus Torvalds2010/07/19 06:27 PM
                              150 GFLOP/s measured?Anon2010/07/19 08:54 PM
                                150 GFLOP/s measured?anon2010/07/19 10:45 PM
                        150 GFLOP/s measured?hobold2010/07/19 08:14 AM
                          150 GFLOP/s measured?Linus Torvalds2010/07/19 10:56 AM
                            150 GFLOP/s measured?a reader2010/07/21 07:16 PM
                              150 GFLOP/s measured?Linus Torvalds2010/07/21 08:05 PM
                                150 GFLOP/s measured?anon2010/07/22 01:09 AM
                                  150 GFLOP/s measured?a reader2010/07/22 06:53 PM
                                    150 GFLOP/s measured?gallier22010/07/23 04:58 AM
                                      150 GFLOP/s measured?a reader2010/07/25 07:35 AM
                                        150 GFLOP/s measured?David Kanter2010/07/25 10:49 AM
                                          150 GFLOP/s measured?a reader2010/07/26 06:03 PM
                                            150 GFLOP/s measured?Michael S2010/07/28 12:38 AM
                                              150 GFLOP/s measured?Gabriele Svelto2010/07/28 12:44 AM
                                    150 GFLOP/s measured?anon2010/07/23 03:55 PM
                                      150 GFLOP/s measured?slacker2010/07/23 11:48 PM
                                        150 GFLOP/s measured?anon2010/07/24 01:36 AM
                                    150 GFLOP/s measured?Vincent Diepeveen2010/07/27 04:37 PM
                                      150 GFLOP/s measured??2010/07/27 10:42 PM
                                        150 GFLOP/s measured?slacker2010/07/28 04:55 AM
                                      Intel's clock rate projectionsAM2010/07/28 01:03 AM
                                        nostalgia ain't what it used to besomeone2010/07/28 04:38 AM
                                          Intel's clock rate projectionsAM2010/07/28 09:12 PM
                        Separate the OoO-ness from speculative-ness?2010/07/20 06:19 AM
                          Separate the OoO-ness from speculative-nessMark Christiansen2010/07/20 01:26 PM
                          Separate the OoO-ness from speculative-nessslacker2010/07/20 05:04 PM
                            Separate the OoO-ness from speculative-nessMatt Sayler2010/07/20 05:10 PM
                              Separate the OoO-ness from speculative-nessslacker2010/07/20 08:37 PM
                                Separate the OoO-ness from speculative-ness?2010/07/20 10:51 PM
                                  Separate the OoO-ness from speculative-nessanon2010/07/21 01:16 AM
                                    Separate the OoO-ness from speculative-ness?2010/07/21 06:05 AM
                                      Software conventionsPaul A. Clayton2010/07/21 07:52 AM
                                        Software conventions?2010/07/22 04:43 AM
                                      SpeculationDavid Kanter2010/07/21 09:32 AM
                                        Pipelining affects the ISA?2010/07/22 09:58 PM
                                          Pipelining affects the ISA?2010/07/22 10:14 PM
                                          Pipelining affects the ISArwessel2010/07/22 11:03 PM
                                            Pipelining affects the ISA?2010/07/23 04:50 AM
                                            Pipelining affects the ISA?2010/07/23 05:10 AM
                                              Pipelining affects the ISAThiago Kurovski2010/07/23 01:59 PM
                                                Pipelining affects the ISAanon2010/07/24 06:35 AM
                                                  Pipelining affects the ISAThiago Kurovski2010/07/24 10:12 AM
                                          Pipelining affects the ISAGabriele Svelto2010/07/26 01:50 AM
                                            Pipelining affects the ISAIlleglWpns2010/07/26 04:14 AM
                                              Pipelining affects the ISAMichael S2010/07/26 02:33 PM
                                      Separate the OoO-ness from speculative-nessanon2010/07/21 04:53 PM
                                        Separate the OoO-ness from speculative-ness?2010/07/22 03:15 AM
                                          Separate the OoO-ness from speculative-nessanon2010/07/22 03:27 AM
                                      Separate the OoO-ness from speculative-nessslacker2010/07/21 06:45 PM
                                        Separate the OoO-ness from speculative-nessanon2010/07/22 12:57 AM
                                        Separate the OoO-ness from speculative-ness?2010/07/22 04:26 AM
                                          Separate the OoO-ness from speculative-nessDan Downs2010/07/22 07:14 AM
                                          Confusing and not very useful definitionDavid Kanter2010/07/22 11:41 AM
                                            Confusing and not very useful definition?2010/07/22 09:58 PM
                                              Confusing and not very useful definitionUngo2010/07/24 11:06 AM
                                                Confusing and not very useful definition?2010/07/25 09:23 PM
                            Separate the OoO-ness from speculative-nesssomeone2010/07/20 07:02 PM
                              Separate the OoO-ness from speculative-nessThiago Kurovski2010/07/21 03:13 PM
            You are just quoting SINGLE precision flops? OMG what planet do you live? Vincent Diepeveen2010/07/19 09:26 AM
              The prior poster was talking about SP (NT)David Kanter2010/07/19 10:34 AM
                All FFT's need double precisionVincent Diepeveen2010/07/19 01:02 PM
                  All FFT's need double precisionDavid Kanter2010/07/19 01:09 PM
                    All FFT's need double precisionVincent Diepeveen2010/07/19 03:06 PM
                  All FFT's need double precision - notMichael S2010/07/20 12:16 AM
                    All FFT's need double precision - notUngo2010/07/20 11:04 PM
                      All FFT's need double precision - notMichael S2010/07/21 01:35 PM
                      All FFT's need double precision - notEduardoS2010/07/21 01:52 PM
                        All FFT's need double precision - notAnon2010/07/21 04:23 PM
                          All FFT's need double precision - notRicardo B2010/07/26 06:46 AM
                        I'm on a boat!anon2010/07/22 10:42 AM
                        All FFT's need double precision - notVincent Diepeveen2010/07/24 10:39 PM
                          All FFT's need double precision - notslacker2010/07/25 02:27 AM
                            All FFT's need double precision - notRicardo B2010/07/26 06:40 AM
                          All FFT's need double precision - notEduardoS2010/07/25 07:37 AM
                            All FFT's need double precision - notMichael S2010/07/25 09:43 AM
                    All FFT's need double precision - notVincent Diepeveen2010/07/24 10:19 PM
      A bit off baseEduardoS2010/07/08 03:08 PM
        A bit off baseGroo2010/07/08 05:11 PM
          A bit off basejohn mann2010/07/08 05:58 PM
            All right...let's cool it...David Kanter2010/07/08 06:54 PM
    A bit off baseVincent Diepeveen2010/07/19 02:36 PM
Reply to this Topic
Name:
Email:
Topic:
Body: No Text
How do you spell avocado?