14 GB RAM in MacPro Quad Nehalem

Discussion in 'Mac Pro' started by Mac Hammer Fan, Dec 18, 2010.

  1. Mac Hammer Fan macrumors 6502

    Mac Hammer Fan

    Joined:
    Jul 13, 2004
    Location:
    Belgium
    #1
    I added a 2 GB RAM module in the fourth memory slot and have now 14 GB RAM installed. I ran Xbench and I got the same results in the memory speed test. I checked the memory with the memory slot utility and Techtool Pro and everything is fine. I know that triple channel is optimal, but 14 GB RAM seems to work too.
     
  2. Hellhammer Moderator

    Hellhammer

    Staff Member

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    Dec 10, 2008
    Location:
    Finland
    #2
    Your 3x4GB should still run in triple-channel and the fourth module should run in single-channel, that's why there is no difference. Tri-channel provides very little in real world as most apps can't take advantage of the extra memory bandwidth that it provides.

    IMO more RAM > memory bandwidth
     
  3. Mac Hammer Fan thread starter macrumors 6502

    Mac Hammer Fan

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    Belgium
  4. Umbongo macrumors 601

    Umbongo

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    Sep 14, 2006
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    England
    #4

    It actually makes it run in dual channel, although the performance is faster than you would from a true dual channel memory system. The difference between any of them in the real world for most applications of course is negligable.
     
  5. Mac Hammer Fan thread starter macrumors 6502

    Mac Hammer Fan

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    #5
    Only Open GL seems to be slightly slower (according to XBench)
     
  6. VirtualRain macrumors 603

    VirtualRain

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    Aug 1, 2008
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    Vancouver, BC
    #6
    This topic comes up regularly. I did some poking around last time this game up and unearthed this useful tid-bit from AnandTech on how Intel handles 4 DIMMS on three channels...

    Source... http://www.anandtech.com/show/2658/5
     
  7. Umbongo macrumors 601

    Umbongo

    Joined:
    Sep 14, 2006
    Location:
    England
    #7
    That is how I assumed it worked too originally, however Dell, Sun and Supermicro disagree as do the benchmarks. Also logically it woudn't make sense to have unbalanced performance on such hardware, especially when all other aspects of using unbalanced memory seek to balance.


    http://www.delltechcenter.com/page/04-08-2009+-+Nehalem+and+Memory+Configurations?t=anon
     
  8. johnnymg macrumors 65816

    johnnymg

    Joined:
    Nov 16, 2008
    #8
    I went from a 3x2GB to a 4x4GB configuration on my 2010 3.2 Quad. Geekbench (32 bit) dropped <1% with the 4 module configuration so the real world difference is non-existent between these mem configurations.

    JohnG
     
  9. VirtualRain macrumors 603

    VirtualRain

    Joined:
    Aug 1, 2008
    Location:
    Vancouver, BC
    #9
    Well I guess that's the most definitive source we've got on this subject. Good find.
     
  10. mjsmke macrumors 6502a

    Joined:
    Mar 2, 2010
    Location:
    UK
    #10
    I was running with 3x4GB for a while then put in a spare 2GB stick about 2 months ago. I didn't notice any loss in speed. But having the extra 2GB helps me alot sometimes.
     

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