2 Replies Latest reply: Jan 8, 2013 8:07 AM by Grant Bennet-Alder
Chris Winkler1 Level 2 (165 points)

I have a Mac Pro 2x 2.4GHz 6-core Xeon processors & I want to upgrade the RAM. It came with 6x 2GB DIMMS, and I bought 4x 8X DIMMS. I would like to use 4x of the 2GB, for a total of 40GB. Does it matter how or where I put the DIMMS, as I am filling all the slots, or should i do one of the following;


1 Bank all 4X 8GB and the other 4x 2GB or

1 bank 2x 8GB and 2X 2GB and the same for the other bank


or does it really even matter?


Thank you in advance for any help.

Mac Pro, OS X Mountain Lion (10.8.2), 1TBHD, 12GB Ram
  • Allan Eckert Level 8 (49,730 points)

    It is my understanding that your plan B where the memory on both banks is balanced is the prefered configuration.



  • Grant Bennet-Alder Level 9 (55,305 points)

    Allan has it right for that Mac.


    The difficulty is that different large-sized modules have a habit of not playing nice with smaller modules. Also, slot 3 is shared with slot 4 on each side, so leave those empty until you know every module works independently.


    I suggest you install all your new modules first, balanced across the two sides. "Install in pairs" is not used in this model. Lowest numbered slots in each group (front left and right rear) first. so that is new modules in 1, 2 and 5, 6.


    ¿Are all modules working that way?

    -Yes, add an old module to slot 3 and 7 and re-test

    -No, find non-working modules and test with ONLY those modules


    ¿Old and new working in 3 slots on each side?

    -Yes, try adding in the fourth on each side

    -No, try old modules swapped around with each other, but you may have to leave the last slot empty on each side.