Installing RAM in Mac Pro

Discussion in 'Mac Basics and Help' started by JochemWeierink, Sep 24, 2009.

  1. JochemWeierink macrumors newbie

    Sep 24, 2009
    Hi everyone

    Today I got my additional 12 gigs of ram ( 3 x 4 GB Kingston pc3 - 85000 Parity REG CL7 DIMM) for my mac pro( 2 x 2.26 GHz Quad-Core Intel Xeon
    I tried to install the 12 gigs ( 3 x 4 GB) next to the 4 x 2 gigs I already had ( 2GB 2RX8 PC3-8500e-7-10-E0, DDR3, 1066, CL7, ECC, (just typed it over:p)
    anyways when I try to start my mac pro the only thing he does is flashing his standbye light... the only thing what works is or the 12 gigs alone or the 8 gigs alone but he doesnt like the combination... somebody HELP! :p I hope I dint waste a lot of money


  2. patrick0brien macrumors 68040


    Oct 24, 2002
    The West Loop

    Mac Pro’s are sensitive to how the DIMMs are ordered in the risers.

    1. It is always best to have the same amount of RAM in each Riser.
    2. It is wise to have symmetry in your risers, like 2gb, 4gb, 4gb, 2gb
    3. It is good to mirror the DIMMs from on riser to the other. Meaning that if your DIMM order on one riser is 2gb, 4gb, 4gb, 2gb, you’ll want the same on the other.

    However, it seems you have an odd number of DIMMs. I’d recommend you test your rig with the configuration 2, 4, x, 2 on each riser, this would leave you with one 4gb DIMM left over. This would leave you with 16gb of total RAM. If that works, replace one of your 4gb DIMMs with the leftover and test again.

    If all is well in both scenarios, I would recommend getting one more 4gb DIMM to allow full parity and interleaving. With the Riser configuration of 2,4,4,2 in both risers.

    I am curious as to how well the Pro will deal with RAM space bigger than 16gb. Will it work with more? If it does, let me know, I’d love to move to 32gb.
  3. gianklain macrumors newbie

    Sep 24, 2009
    Same problem

  4. JochemWeierink thread starter macrumors newbie

    Sep 24, 2009
    Thanks for the advice,

    But I tried every possible combination and the only thing that works is or the 8 GIGS or the 12 GIGS, I think I just sell the 8 gigs and buy another 4 gig for it.
    Maybe someone can help me with finding out from wich company my 8 gigs are... so I can sell them :) I tried to find it out myself but I couldnt find it. (I got them when I bought my macpro apple build them in..



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