Memory Puzzle

Discussion in 'Mac Pro' started by phaedo5, May 11, 2009.

  1. phaedo5 macrumors newbie

    Jan 13, 2009
    Ok, so I know memory has to be installed in pairs. I'm trying to do that, but it's not recognizing all of my memory. So I'm trying to figure out where I went wrong (which I surely did).

    I have a Mac Pro, little over a year old.

    I had the 2GB standard memory installed. So I bought 8GB more (4 x 2GB sticks). I tried following the manual. I ended up with two pairs on top (basically all four 2GB sticks) and one pair on bottom (two 1GB sticks).

    This seemed to be what the manual said. Two pairs on top and one pair on bottom for 6 sticks.

    But it only seems to be recognizing 8GB now. Where did I go wrong? I need help!?!
  2. Rt&Dzine macrumors 6502a


    Oct 8, 2008
    Try a pair of the 2GBs on each riser, not all four 2GBs on the same riser:

    2GB x 2 in the first bank, the 1GB x 2 in 2nd bank for top riser, and 2GB x 2 in lower riser


    1GB x 2 + 2.0GB x 2 in top riser, 2GB x 2 in lower riser (1GB modules in first bank)

    EDIT: I'm assuming you have a 2008 model.
  3. Dr.Pants macrumors 65816


    Jan 8, 2009
    I was under the assumption that pairing memory meant that the DIMM in slot one, riser one, had to match slot one, riser two...

    EDIT - I am wrong (coming from installing another 4 GB RAM in G5). But I found this -
    from (thank you TMR812 for posting)

    10 GB total? According to the graph, you need a pair of 2GB sticks and a pair of 1 GB sticks on top, and a pair of 2 GB sticks on the bottom.

    It would help to know your MacPro model.
  4. phaedo5 thread starter macrumors newbie

    Jan 13, 2009
    Yes! Exactly right. And thank you Dr. Pants for that graphic. That's great.

    It was 2 x 2GB + 2 x 1GB on top and the final 2 x 2GB on bottom. Works perfect.

    And sorry for not providing the model. When you ask for that, are you wanting the build number? I never know. There are so many versions of Mac computers. My build is Build 9G55, if that would have helped.

    Or were you just wanting to know that it is a Quad-Core Intel Xeon?

    Just curious for the next time I come here looking for help. But again, thank you all!
  5. Genghis Khan macrumors 65816

    Genghis Khan

    Jun 3, 2007
    Melbourne, Australia

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