Mac Pro ram config

Discussion in 'Mac Pro' started by bniu, Oct 7, 2011.

  1. bniu macrumors 6502a

    Mar 21, 2010
    i read somewhere that it is preferable for the Mac Pro to have memory installed with either 3 or 6 modules for a total RAM amount in multiples of three. Why is this that the Mac Pro works best in multiples of 3 (i.e. 3, 6, 12, 24, 48, 96)? I thought RAM is usually ideally configured in powers of 2 (2,4,8,16,32,64).
  2. prestonkd, Oct 7, 2011
    Last edited: Oct 7, 2011

    prestonkd macrumors member


    Jun 15, 2007
  3. CaptainChunk macrumors 68020


    Apr 16, 2008
    Phoenix, AZ
    This is because the Nehalem/Woodcrest (2009/2010) Mac Pros use a triple-channel memory controller. Thus, sets of 3 is ideal. But the performance difference when installing RAM in dual-channel configuration is generally negligible for most uses.

    Oddly, the 2009/2010 Mac Pros have 4 or 8 slots (depending on whether it's SP or DP, respectively). But the base RAM configurations are 3 or 6GB, installed in tri-channel configuration. They really should equip the machines with 6 or 12 slots, but for whatever reason (maybe space concerns), they don't.

    I wouldn't totally worry about triple channel if you prefer more RAM and want to fill all the slots. For example, newer versions of After Effects will prefer a 16GB machine in dual-channel configuration versus a 12GB machine in tri-channel.

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