Having RAM in this order, is it slower?

Discussion in 'Mac Pro' started by MythicFrost, Oct 6, 2009.

  1. MythicFrost macrumors 68040

    MythicFrost

    Joined:
    Mar 11, 2009
    Location:
    Australia
    #1
    Hey, I've got 18GB of RAM in my MP, I thought I read something about it being faster if you put them in a certain order, or use all the same modules.
    So I'm wondering if anyone knows if this order/or these modules will be slower than say, some other order, or if they were all 4GB modules:

    • DIMM A/DIMM 1 1GB
    • DIMM A/DIMM 2 1GB
    • DIMM A/DIMM 3 2GB
    • DIMM A/DIMM 4 2GB
    • DIMM B/DIMM 1 2GB
    • DIMM B/DIMM 2 2GB
    • DIMM B/DIMM 3 4GB
    • DIMM B/DIMM 4 4GB

    Kind Regards
     
  2. Tesselator macrumors 601

    Tesselator

    Joined:
    Jan 9, 2008
    Location:
    Japan
    #2

    Yes, there will be some differences, including to do with speed. Use this chart to get it right:

    [​IMG]
     
  3. MythicFrost thread starter macrumors 68040

    MythicFrost

    Joined:
    Mar 11, 2009
    Location:
    Australia
    #3
    Thanks.

    If I have 18GB, does 9A apply? I do 4x2GB on the right, and 2x4GB at the top two, and then 2x1GB at the bottom 2?

    Kind Regards
     
  4. gugucom macrumors 68020

    gugucom

    Joined:
    May 21, 2009
    Location:
    Munich, Germany
    #4
    Your best bet would be:

    • DIMM A/DIMM 1 4GB
    • DIMM A/DIMM 2 4GB
    • DIMM A/DIMM 3 empty
    • DIMM A/DIMM 4 empty
    • DIMM B/DIMM 1 2GB
    • DIMM B/DIMM 2 2GB
    • DIMM B/DIMM 3 2GB
    • DIMM B/DIMM 4 2GB

    You will provide the fastest access to your memory by that way. It will exceed the effect of having 2 GB more RAM. If you really need the 2 GB:


    • DIMM A/DIMM 1 4GB
    • DIMM A/DIMM 2 4GB
    • DIMM A/DIMM 3 1GB
    • DIMM A/DIMM 4 1GB
    • DIMM B/DIMM 1 2GB
    • DIMM B/DIMM 2 2GB
    • DIMM B/DIMM 3 2GB
    • DIMM B/DIMM 4 2GB

    Would be better. If you want to upgrade buy 2 more 4GB sticks and fit them like this:

    • DIMM A/DIMM 1 4GB
    • DIMM A/DIMM 2 4GB
    • DIMM A/DIMM 3 2GB
    • DIMM A/DIMM 4 2GB
    • DIMM B/DIMM 1 4GB
    • DIMM B/DIMM 2 4GB
    • DIMM B/DIMM 3 2GB
    • DIMM B/DIMM 4 2GB
     
  5. Tesselator macrumors 601

    Tesselator

    Joined:
    Jan 9, 2008
    Location:
    Japan
    #5

    Yeah, just use the logic of the graph to figure out where the 4GB modules go.

    9A looks right for that.
     
  6. ungraphic macrumors 6502a

    ungraphic

    Joined:
    Nov 15, 2007
    Location:
    Toronto, Canada
    #6
    Hmm, good thread. Here's my setup. Someone tell me if its proper;

    • DIMM A/DIMM 1 2GB
    • DIMM A/DIMM 2 2GB
    • DIMM A/DIMM 3 512mb
    • DIMM A/DIMM 4 512mb
    • DIMM B/DIMM 1 512mb
    • DIMM B/DIMM 2 512mb
    • DIMM B/DIMM 3 empty
    • DIMM B/DIMM 4 empty
     
  7. Genghis Khan macrumors 65816

    Genghis Khan

    Joined:
    Jun 3, 2007
    Location:
    Melbourne, Australia
    #7
    Yep, That's right.

    Basically, install in matching pairs (with both riser cards mirrored if possible), and the biggest chips on the inner slots.
     
  8. MythicFrost thread starter macrumors 68040

    MythicFrost

    Joined:
    Mar 11, 2009
    Location:
    Australia
    #8
    Would this be better for me Riser A 4/2/2/1, Riser B 4/2/2/1 compared to what I currently have Riser A, 2/2/1/1, Riser B 2/2/4/4.

    Kind Regards
     
  9. Umbongo macrumors 601

    Umbongo

    Joined:
    Sep 14, 2006
    Location:
    England
    #9
    512mb modules slow down the Mac Pro due to being single rank and the smaller capcaity also affects the speed. I understand it may not be viable to change them out for something else though. Use 6c from the chart for optimum performance.

    That's not a correct setup as slots 1&2 and 3&4 need to match. Either a:4/4/1/1 b:2/2/2/2 for capacity or a:4/4/-/- b:2/2/2/2 for speed. You may not notice a speed increase with what you are doing, but it will be faster.
     
  10. gugucom macrumors 68020

    gugucom

    Joined:
    May 21, 2009
    Location:
    Munich, Germany
  11. ungraphic macrumors 6502a

    ungraphic

    Joined:
    Nov 15, 2007
    Location:
    Toronto, Canada
    #11
    Awesome! Thank you!!
     

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