New Mac Pro - 4th memory slot

Discussion in 'Mac Pro' started by voyager77, Jan 2, 2015.

  1. voyager77 macrumors member

    Jun 25, 2012
    I just got a new mac pro with 12 Gb of ram.
    This means the 4th memory slot is empty and wanting to be filled asap.

    Now what fits in there best?
    Of course it has to be the same type that's in the other slots, so i'll be going with the Apple stuff.

    But does it have to be a 4 Gb module, or can i put in an 8 Gb or even a 16?
    Are there any downsides to not having "paired" slots?
  2. Demigod Mac macrumors 6502a

    Apr 25, 2008
  3. bxs macrumors 6502a

    Oct 20, 2007
    Seattle, WA
    You can install a 4GB or an 8GB spec-matching module in that 4th slot. However, you cannot and must not mix 4 and 8GB modules with 16 and 32GB modules.

    Pull up the About This Mac and select the Memory tab for an explanation and/or goto
  4. h9826790 macrumors G5


    Apr 3, 2014
    Hong Kong
    I think it's not the matter of RAM size, but the spec. If there is a 32G 1866 UDIMM ECC DDR3, you may use it with the 4G 1866 UDIMM ECC DDR3 RAM without any trouble.

    The real problem is that the 32G stick is RDIMM at this moment. And mixing UDIMM with RDIMM will crash the system.
  5. mintakax macrumors regular

    Dec 19, 2013
    That's what she said :)

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