Mixed-sized DIMMs - layout?

Discussion in 'Mac Pro' started by CaptainJeff, Jun 19, 2012.

  1. CaptainJeff macrumors member

    Joined:
    Apr 16, 2009
    Location:
    Elkridge, Maryland; USA
    #1
    I've got an early-2009 8-core Mac Pro, currently equipped with 8GB of RAM (four 2GB modules). I've ordered 16GB of additional RAM (four 4GB modules). Does it matter how I arrange these among the eight slots?
     
  2. flatfoot macrumors 65816

    Joined:
    Aug 11, 2009
    #2
  3. CaptainJeff thread starter macrumors member

    Joined:
    Apr 16, 2009
    Location:
    Elkridge, Maryland; USA
    #3
    To answer my own question, I popped these new 4GB modules in last night. I originally had two 2GB modules in each set of DIMM slots (in positions 1/2 and 5/6). I added the two 4GB modules to each set (in positions 3/4 and 7/8).

    Sure enough, the memory slot configuration tool popped up, telling me I had a non-optimal configuration. OSX wanted the 4GB modules in the first slots in each set and the 2GB modules in the second pair of slots. So, I ended up swapping everything with two 4GB modules in the first slots (1/2 and 5/6) and the two 2GB modules in the second slots (3/4 and 7/8) for each set. Boot it up and the memory slot configuration tool informed me that I was now optimal.
     
  4. flatfoot macrumors 65816

    Joined:
    Aug 11, 2009
    #4
    That's what I meant to imply by writing "4422". ;)
     

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