12-core: 24 or 32GB RAM?

Discussion in 'Mac Pro' started by Garamond, Sep 3, 2010.

  1. Garamond macrumors regular

    Joined:
    Oct 17, 2004
    #1
    I've heard it might be better using only three 8GB-sticks (for higher memory speed)? I have ordered four of them - would there be any reason why I shouldn't put them all in for 32GB?
     
  2. Hellhammer Moderator

    Hellhammer

    Staff Member

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    Dec 10, 2008
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    Finland
    #2
    Triple-channeling offers little to nothing in real world. Theoretically, it offers 50% greater memory bandwidth but not many apps can really take advantage of it. If you already bought all 4 modules, just put them all in. Of course if your apps can take advantage of the extra bandwidth, then three modules would be better but it's hard to say as you did not specify your usage
     
  3. mulo macrumors 68020

    mulo

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    #3
    2x dual channel setup is gonna be faster then 1x triple channel setup, just saying.
     
  4. cnstoll macrumors 6502

    Joined:
    Aug 29, 2010
    #4
    Definitely 32GB, if you already have the module.

    What happens with the memory controller on the Nehalem CPUs in a 4-bank configuration is that the first three modules are treated in a triple channel fashion, and the 4th module is treated as single channel. That way you get full 25GB/s bandwidth to the 24GB of RAM. But, if you do fill that up...you're only going to get 8.6~GB/s bandwidth for the last 8GB.

    So it's really not going to hurt you much to go to 32. And if you're running applications that take advantage of that much RAM, then the additional benefit of not having to page out to disk as often in order to free up space in memory is going to far outweigh the loss of bandwidth to one of your RAM modules.

    http://www.anandtech.com/show/2658/5
     
  5. CaoCao macrumors 6502a

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    Jul 27, 2010
  6. Garamond thread starter macrumors regular

    Joined:
    Oct 17, 2004
    #6
    Thanks for the input, guys. I'll be running heavy documents in Indesign CS5 so I really need as much RAM as I can get. It's a memory hog.
     
  7. mulo macrumors 68020

    mulo

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    Aug 22, 2010
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    #7
    well you answered your question yourself then :)
     

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