gpgpu

Article: Predicting AMD and Nvidia GPU Performance
By: EduardoS (no.delete@this.spam.com), April 17, 2011 12:31 pm
Room: Moderated Discussions
Vincent Diepeveen (diep@xs4all.nl) on 4/16/11 wrote:
---------------------------
>Besides that the new 6000 series has 2.5x more multiplication resources than the
>5000 series for the very crucial 32 x 32 bits.

No... Barts still only does 32 x 32 bits multiplication on T unit, like Cypress, Cayman take it's four units for a single 32 x 32 bits, no 2.5x improvement here.


>Which for gpgpu matters really a lot.

No it doesn't, 32 bits multiplication is pretty rare and hardware designer gives much importance to it.

>Let me quote a few gpu programmers here.

Let's skip this part, just bullshit.

>Nvidia will do great in games and will remain doing great in games.

Let's see... GTX590 vs HD6990... A same TDP, same performance and manufacturing tech nVidia needs 35% more die size... Not exactly "doing great". And Cayman doesn't have that good performance/area...

>He's comparing Fermi, the first generation Nvidia that has 32 x 32 bits multiplication
>(it was 24 bits multiplication before) versus old generation AMD that did have 32
>bits multiplication, but only what was it 1 unit out of 5.

If I remeber correctly Fermi does 32 bits multiplication at half speed... I told you, nobody cares.

>Todays generation, just like nvidia, has been more optimized for that.

In nVidia case, yes, in AMD case, no, in nVidia case it's more like a side effect.

>How long does AMD need there?

12 cycles... And nVidia takes weel more than 4 cycles too, I don't know exactly, something between 20 and 30 cycles.

>I don't know, but for what i'm programming in opencl right now it's pretty crucial to know.

If all you care is a 3-way add you should stay away from OpenCL...

Few who write OpenCL code knows exactly how long each operation takes, it doesn't matter, it matter less than on CPUs and still, many CPU programmers can write good code while having no idea how long each operation take.

>Here is another thing we don't know about gpgpu. How *reliable* are results calculated by gpgpu?

If your code relies on 1+1=2 then it's very reliable.

GPUs are deterministic, all integer operations will give the same results a CPU would, fp operations may differ from CPU results, but the same input will always return the same result up to (I hope for a doc quoting the value) a given precision, if you don't rely on the bits beyond this point it's reliable.

>As all calculations are parallel, in gpgpu you will not have deterministic behaviour.

The GPU will, but buggy code relying on undefined behaviour won't.

>How many errors do the gpu's make there however in calculations?

Not more than CPUs in the same conditions...

>So not RAM errors, but errors of the execution units because of the huge heat and
>power

This makes Power7 unreliable?

>without any software out there that checks for correctness.

It's your option...

>The cheapest nvidia to do serious gpgpu with is the Quadro 6000. The gamers cards all are lobotomized too much there.

Now the important is DP and not 32 multiplication anymore?
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TopicPosted ByDate
New Article: Predicting GPU Performance for AMD and NvidiaDavid Kanter2011/04/11 11:55 PM
  Graph is not red-green colorblind friendly (NT)RatherNotSay2011/04/12 03:51 AM
    FixedDavid Kanter2011/04/12 08:46 AM
  New Article: Predicting GPU Performance for AMD and NvidiaJames2011/04/12 12:30 PM
    New Article: Predicting GPU Performance for AMD and NvidiaDavid Kanter2011/04/12 02:51 PM
  Try HD6450 or HD6850EduardoS2011/04/12 03:31 PM
    Try HD6450 or HD6850David Kanter2011/04/13 10:25 AM
      Try HD6450 or HD6850EduardoS2011/04/13 03:20 PM
        of causeMoritz2011/04/14 08:03 AM
          of causeEduardoS2011/04/14 01:55 PM
            Barts = 5DMoritz2011/04/14 09:26 PM
              Barts = 5DAntti-Ville Tuunainen2011/04/15 12:38 AM
                Limiting fixed function unitsMoritz2011/04/15 04:28 AM
                  Limiting fixed function unitsVincent Diepeveen2011/04/20 02:38 AM
                    lack of detailMoritz2011/04/20 09:24 AM
                      lack of detailEduardoS2011/04/20 11:45 AM
            gpgpuVincent Diepeveen2011/04/16 02:10 AM
              gpgpuEduardoS2011/04/17 12:31 PM
                gpgpuGroo2011/04/17 12:58 PM
                  gpgpuEduardoS2011/04/17 01:08 PM
                  gpgpuIan Ameline2011/04/18 03:55 PM
                    gpgpuPing-Che Chen2011/04/19 12:59 AM
                      GPU numerical complianceSylvain Collange2011/04/19 11:38 AM
                        GPU numerical complianceVincent Diepeveen2011/04/20 02:17 AM
                gpgpuVincent Diepeveen2011/04/20 02:02 AM
                  gpgpu and core countsHeikki Kultala2011/04/20 04:41 AM
                    gpgpu and core countsVincent Diepeveen2011/04/20 05:52 AM
                      gpgpu and core countsnone2011/04/20 07:05 AM
                        gpgpu and core countsEduardoS2011/04/20 11:36 AM
                      gpgpu and core countsHeikki Kultala2011/04/20 10:16 AM
                        gpgpu and core countsEduardoS2011/04/20 11:34 AM
                          gpgpu and core countsHeikki Kultala2011/04/20 07:24 PM
                            gpgpu and core countsEduardoS2011/04/20 08:55 PM
                              gpgpu and core countsHeikki Kultala2011/04/21 06:48 AM
                                gpgpu and core countsEduardoS2011/04/22 01:41 PM
                              AMD Compute and Texture FetchDavid Kanter2011/04/21 10:42 AM
                                AMD Compute and Texture FetchVincent Diepeveen2011/04/22 01:14 AM
                                  AMD Compute and Texture FetchDavid Kanter2011/04/22 10:53 AM
                                AMD Compute and Texture FetchEduardoS2011/04/22 01:46 PM
                                  AMD Compute and Texture FetchDavid Kanter2011/04/22 02:02 PM
                                    AMD Compute and Texture FetchEduardoS2011/04/22 02:18 PM
                                    AMD Compute and Texture Fetchanon2011/04/22 03:30 PM
                                      AMD Compute and Texture FetchDavid Kanter2011/04/22 09:17 PM
                        gpgpu and core countsVincent Diepeveen2011/04/20 12:12 PM
                          gpgpu and core countsHeikki Kultala2011/04/21 10:23 AM
                            gpgpu and core countsVincent Diepeveen2011/04/22 02:11 AM
                              Keep the crazy politics out of thisDavid Kanter2011/04/22 08:39 AM
                                Keep the crazy politics out of thisVincent Diepeveen2011/04/22 09:12 AM
                                  Keep the crazy politics out of thisDavid Kanter2011/04/22 10:44 AM
                              gpgpu and core countsJouni Osmala2011/04/22 11:06 AM
                  gpgpuEduardoS2011/04/20 11:59 AM
                    gpgpuVincent Diepeveen2011/04/20 12:37 PM
                      gpgpuEduardoS2011/04/20 05:27 PM
                        gpgpuVincent Diepeveen2011/04/21 02:06 AM
                          gpgpuEduardoS2011/04/22 02:00 PM
  New Article: Predicting GPU Performance for AMD and NvidiaPiedPiper2011/04/12 10:05 PM
    New Article: Predicting GPU Performance for AMD and NvidiaDavid Kanter2011/04/12 10:42 PM
      New Article: Predicting GPU Performance for AMD and NvidiaMS2011/04/15 05:04 AM
        New Article: Predicting GPU Performance for AMD and NvidiaKevin G2011/04/16 02:25 AM
          New Article: Predicting GPU Performance for AMD and NvidiaDavid Kanter2011/04/16 08:42 AM
          New Article: Predicting GPU Performance for AMD and NvidiaVincent Diepeveen2011/04/20 02:20 AM
    memoryMoritz2011/04/14 09:03 PM
      memory - moreMoritz2011/04/15 11:11 PM
  New Article: Predicting GPU Performance for AMD and NvidiaKevin G2011/04/14 11:30 AM
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