Will Installing unmatched pairs degrade performance

Discussion in 'Mac Pro' started by kimo2u, Sep 17, 2007.

  1. kimo2u macrumors newbie

    Sep 17, 2007
    I just purchased a Mac Pro 3 Ghz quad core machine.

    It has 1 gig of factory installed RAM.

    I purchased 8 gigs ( 4 x 2 gigs) of RAM from a vendor to save $$$.

    The install instructions state that dimms must be installed in equal pairs of equal size from the same vendor.

    Does this mean that I need to take out the one gig thats in there and install the 4 X 2 gig dimms?

    What will the ramifications of leaving the original ram installed and adding the 8 gig?

    Will this damage the machine and void it's warranty?

    Will this compromise the machines performance because its not a matched pair?

    Thanks in advance.
  2. bigbird macrumors 6502

    Aug 17, 2007
    Put the 4 X 2GB sticks in riser A (top riser). Move the 2 X 512MB to the lower riser (B). The matched 4 X 2 in the upper riser will operate at the optimum speed. The 2 X 512 will operate with less efficiency, but will be called on only after the 8GB has been alloted.
  3. Spikeanator6982 macrumors 6502

    Jun 13, 2007
    I guess from what i have read..he should put 2by2GB in the top first slots and 2 by2GB in the bottom first slots, and put the 2by512MB in the top 3rd and 4th slots. That way, he can use quad for 8GB before he goes to dual channel with the 2, 512MB moduels.
  4. betelgeuse1 macrumors member


    Nov 5, 2004
    No, installing the 4x2GB DIMM's in addition to the existing 1GB will not damage your machine and should not void your warranty. There is some debate as to whether you will really see any measurable performance difference in which slots you seat the different capacity DIMM's. The "matched" pairs referred to are related to the layout of the riser cards. There are four "pairs" on the cards, two on each card, and within each pair the DIMM's should match in size/vendor/etc. You can have pairs of different sizes on one riser. Hope that makes sense.

Share This Page