Any 32GB RAM module quirks with the nMP?

Discussion in 'Mac Pro' started by Radiating, Apr 24, 2014.

  1. Radiating macrumors 65816

    Dec 29, 2011
    I've been reading up on Mac Pro nuances and I noticed that in some places it says that it doesn't like to mix 32gb modules and modules of other sizes.

    I'm putting together a Mac Pro for a project and plan to run 2x32gb modules, then add another if needed.

    Resellers do sell 3x32gb kits for the Mac Pro, but can anyone tell me if there will be any performance hit if I end up running this setup?

    Can I mix 2x32gb and 2x16gb?
  2. Umbongo macrumors 601


    Sep 14, 2006
    If you have quad-ranked 16GB DIMMs maybe, but you will get single channel performance then. Considering you can only run at 1066MHz with these kits that would be pretty crappy memory bandwidth. Peak transfer rates are like:

    2x32+2x16: 8.5GB/s
    2x32: 17GB/s
    3x32: 25.5GB/s
    4x32: 34GB/s
    4x16GB @ 1866MHz: 60GB/s.

    Some stream benchmarks of 1066MHz quad-channel vs 1866MHz:

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