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Article: Performance Analysis for Core 2 and K8: Part 1
By: Michael S (already5chosen.delete@this.yahoo.com), November 11, 2008 11:15 am
Room: Moderated Discussions
pgerassi (gerassimoff@sbcglobal.net) on 11/11/08 wrote:
---------------------------
>Michael S (already5chosen@yahoo.com) on 11/10/08 wrote:
>---------------------------
>>EduardoS (no@spam.com) on 11/10/08 wrote:
>>---------------------------
>>>Henrik S (henrik.stahl@nospam.oracle.nothanks.com) on 11/10/08 wrote:
>>>---------------------------
>>>>Interesting enough, the NEC submission has a higher peak score (288502 vs 267804)
>>>>despite the fact that it is uses a smaller Java heap and the slower (?) 4 GB DIMMs.
>>>>This is counterintiutive to me and makes me suspect that the AMD Xeon submission
>>>>is on a machine with a less optimized BIOS.
>>>
>>>Registered DIMMs have a significantly lower latency than FB-DIMMs,
>>
>>True
>
>And lower power as well.
>
>>
>>>also FB-DIMM's
>>>latency increase with more DIMMs per channel.
>>>
>>
>>Not in this particular case (8 DIMMs=2 DIMMs/channel). The effect starts from 3-4
>>DIMMs per channel. 2 DIMMs per channel were considered optimal on Blackford. Don't
>>know if the same is true for Seaburg but I don't see why not.
>>
>
>Flat wrong. FB-DIMM latency goes up with each FB-DIMM in a channel as the data
>passes from one FB-DIMM to the next sequentially. So you go from a one hop latency
>to 1.5 hop latency on average, from 1 to 2 FB-DIMMs.
>

The difference between 1 hop vs 1.5 hop is in order of 1 or 2ns (I didn't touch the datasheet for a loooong time, so don't remember an exact number). That difference is more than offset by the opportunity for stores to proceed simultaneously with loads to another DIMM and by doubling the # of ranks. It seems that Blackford memory controller is not very good at opportunistically keeping the pages in open state, so it is important to this chipset to have as many banks as possible.

>Also note that for 16GB configurations, all SPECPOWER Xeon systems have lower results
>than the Opterons of equal speed. The 2384 (2.7GHz) has the highest result at that
>amount of memory, 860 versus 843 (2.8GHz Xeon quad).

Don't see how this is relevant for the discussion that compares two Xeon-based submissions.
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TopicPosted ByDate
Performance analysis of K8 and Core onlineDavid Kanter2008/10/29 01:47 AM
  Performance analysis of K8 and Core onlineJames2008/10/29 02:36 AM
    Performance analysis of K8 and Core onlineMatt Sayler2008/10/29 05:37 AM
    Performance analysis of K8 and Core onlineDavid Kanter2008/10/30 12:00 PM
      Performance analysis of K8 and Core onlineMichael S2008/10/30 06:32 PM
        Performance analysis of K8 and Core onlineDavid Kanter2008/10/31 08:38 AM
        Performance analysis of K8 and Core onlineEduardoS2008/10/31 05:36 PM
          Performance analysis of K8 and Core onlineMichael S2008/11/01 08:21 AM
            Performance analysis of K8 and Core onlineEduardoS2008/11/01 11:15 AM
              Performance analysis of K8 and Core onlineanonymous2008/11/01 01:06 PM
              I stay correctedMichael S2008/11/01 01:53 PM
    Performance analysis of K8 and Core onlineDavid Kanter2008/11/08 06:23 PM
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  Performance analysis of K8 and Core onlinerwessel2008/10/29 11:08 AM
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    Error fixedDavid Kanter2008/11/08 06:22 PM
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      I cache fetches.anon.moose2008/10/31 08:06 AM
        I cache fetches.anon2008/10/31 02:32 PM
          I cache fetches.Peter2008/10/31 03:38 PM
            I cache fetches - clarificationPeter2008/10/31 03:50 PM
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  Performance analysis of K8 and Core onlineHoward Chu2008/10/31 02:39 AM
    Performance analysis of K8 and Core onlineLinus Torvalds2008/10/31 08:08 AM
      Performance analysis of K8 and Core onlineEduardoS2008/10/31 01:11 PM
      Timing sensitive performanceDavid Kanter2008/11/03 09:52 AM
    Performance analysis of K8 and Core onlineDavid Kanter2008/11/01 11:53 PM
      Performance analysis of K8 and Core onlineMichael S2008/11/02 05:12 AM
      Performance analysis of K8 and Core onlineEduardoS2008/11/02 07:47 AM
    Performance analysis of K8 and Core onlineDavid Kanter2008/11/03 11:23 AM
  Shanghai vs Penryn Spec PowerJoe Chang2008/11/09 04:38 PM
    Shanghai vs Penryn Spec PowerEduardoS2008/11/09 05:14 PM
      Shanghai vs Penryn Spec PowerMichael S2008/11/09 06:08 PM
        Shanghai vs Penryn Spec PowerHenrik S2008/11/09 11:52 PM
        Shanghai vs Penryn Spec PowerEduardoS2008/11/10 05:32 AM
          Shanghai vs Penryn Spec PowerMichael S2008/11/10 06:56 AM
            Shanghai vs Penryn Spec PowerEduardoS2008/11/10 12:32 PM
              Shanghai vs Penryn Spec PowerMichael S2008/11/10 05:55 PM
                Shanghai vs Penryn Spec Poweranonymous2008/11/10 08:28 PM
                  Shanghai vs Penryn Spec PowerMichael S2008/11/11 02:32 AM
                    Shanghai vs Penryn Spec Poweranonymous2008/11/11 11:38 AM
                Shanghai vs Penryn Spec Powermpx2008/11/11 02:12 PM
                  Shanghai vs Penryn Spec PowerMichael S2008/11/11 04:39 PM
    Seaburg vs San ClementeMichael S2008/11/09 05:37 PM
      Seaburg vs San ClementeJoe Chang2008/11/09 08:11 PM
    Links to spec.org + commentsHenrik S2008/11/10 03:18 AM
      Links to spec.org + commentsMichael S2008/11/10 04:31 AM
        Links to spec.org + commentsHenrik S2008/11/10 08:09 AM
          Links to spec.org + commentsMichael S2008/11/10 08:58 AM
            Links to spec.org + commentsHenrik S2008/11/10 10:48 AM
      Links to spec.org + commentsEduardoS2008/11/10 05:12 AM
        Links to spec.org + commentsMichael S2008/11/10 07:00 AM
          Links to spec.org + commentspgerassi2008/11/11 10:29 AM
            Links to spec.org + commentsMichael S2008/11/11 11:15 AM
  Performance analysis of K8 and Core onlineaap2008/11/16 05:08 PM
    Performance analysis of K8 and Core onlineDavid Kanter2008/11/16 07:20 PM
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