6 Replies Latest reply: Mar 27, 2011 9:28 AM by River-runner
Jacobo Level 2 (220 points)
Hi there,

Since there seems to be a (slight?) performance advantage when 3 RAM sticks are installed (vs. 2 or 4), what about when more RAM (16 GB) is installed among 2 sockets vs. less RAM (12 GB) is installed among 3 sockets?

Given the current cost of the 8GB memory modules, some insight will be significantly appreciated.

Many thanks,


Mac Pro (3.2 GHz, 4 core Nehalem), Mac OS X (10.6.6), 3 GB RAM
  • Biltan-Wales Level 2 (340 points)
    Hi Jacobo,

    In your position I would opt for the 16GB RAM (2 x 8GB) in preference to 12GB (3 x 4GB).

    I would also recommend 2 x 8GB modules in preference to 4 x 4GB ones, because then you have the option to add up to 2 more 8GB in the future.

    If you buy 4GB memory modules now, your system will be limited to a maximum of 16GB RAM for the future, unless you ditch all of them for larger capacity (currently 8GB) ones.

    At least, if you buy 8GB modules now, you will be better equipped for future expansion.




    16GB RAM (2 x 8GB) installed in 2 memory slots will outperform 12GB RAM (3 x 4GB) installed in 3 memory slots.

    Message was edited by: Biltan-Wales
  • Grant Bennet-Alder Level 9 (56,491 points)
    I agree with Bill. Studies show real-world performance of under five percent from having two modules instead of the optimal three, and this is more than offset by having ENOUGH RAM to keep more stuff in memory.

    I strongly feel that the future expandability issue (buying into the 8GB modules rather than thinking of the 4GB modules as disposable) swamps many other considerations.
  • Jacobo Level 2 (220 points)
    Many thanks Bill and Grant.

    I'll go for a pair of 8GB modules.

    Have a good one,

  • River-runner Level 1 (0 points)
    Yaki da there Biltan,

    Same but different, I have a 2006 Macpro1,1, it's a duel core Xeon. In my memory I have the following:

    DIMM Riser A 1-2 have 512mb DDR2 667 MHz
    DIMM Riser B 1-2 have 1GB
    DIMM Riser A 3-4 have 1GB
    DIMM Riser B 3-4 have 0

    I am going to add the pair of 4's to DIMM Riser B 3-4, I would love to place a pair of 8's but it would be to much for the old girl.

    All the best Gary
  • Grant Bennet-Alder Level 9 (56,491 points)

    The rules for pre-2009 Macs are COMPLETELY different. Posting advice for you in this thread may confuse others reading this information later. Please place your query in a new thread with a distinctive title so readers can offer the best advice for your situation.
  • River-runner Level 1 (0 points)
    No problem mate