Mac Pro (early 2008) RAM Problem

Discussion in 'Mac Pro' started by wellenreiter, Dec 20, 2011.

  1. wellenreiter, Dec 20, 2011
    Last edited: Dec 20, 2011

    wellenreiter macrumors newbie

    Dec 20, 2011
    Hey everyone,
    i got a problem with my Mac Pro.

    I installed 8x1GB RAM on it but i can only see 6GB at the System Profiler.
    The two hidden RAM-modules are perfectly working if i plug them on Riser 1 and 2 in Dual-Mode (Riser A - DIMM 1 // Riser B - DIMM 1).

    The Modules are all grouped in pairs.
    If i change the position of the not working RAM-Modules, they arn't working at the new place.

    What can i do, to fix this problem ??

    I have checked all RAM-Modules in the 2GB Mode (see Screenshot 02).

    Here is my Sytem Configuration:

    Mac OS X 10.6.8
    2,8GHz Quad-Core Intel Xeon

    The new RAM-Modules were bought special for Mac Pro (early 2008) and are FB-DIMMs with ECC.

    Sorry for my bad englisch, i'm german :D

    Thanks for your replys,

    Attached Files:

  2. wafl iron macrumors regular

    Nov 16, 2007
    does the same behavior happen with any other pair when you do the same experiment using the same slots?

    If not, then i would see if your ram seller has a replacement policy.
  3. wellenreiter thread starter macrumors newbie

    Dec 20, 2011
    First, Thanks for the fast answer ;-)

    I forgot to say that i already resent the (in my opinion)damaged RAM-modules back to the Reseller. He gave me new one but they didn't work too.

    All the other Modules are working perfectly in every slot on every riser.
  4. Neodym macrumors 68000


    Jul 5, 2002
    Sounds like your memory daughterboard could be damaged. You could try to have it repaired or to get bigger modules and have only 4 slots populated. The latter would also improve Ram access due to lower latency (inherent in FB-DIMM's).

    (German translation: Möglicherweise ist die Platine defekt, auf der die Module nicht funktionieren. Kannst versuchen, das reparieren zu lassen oder größere Module kaufen und nur 4 Slots bestücken. Letzteres würde auch den Ramzugriff verbessern, da die bei FB-DIMMs systembedingte Zugriffslatenz verringert würde).
  5. wellenreiter thread starter macrumors newbie

    Dec 20, 2011
    hmmm ... i thought the daughterboard could be damaged ... but when i change the position of the damaged RAM, they cant be seen at the new position (in Profiler). For example:

    This is my status:
    Riser A - DIMM 1 - OK
    Riser A - DIMM 2 - OK
    Riser A - DIMM 3 - OK
    Riser A - DIMM 4 - OK

    Riser B - DIMM 1 - empty
    Riser B - DIMM 2 - empty
    Riser B - DIMM 3 - OK
    Riser B - DIMM 4 - OK

    If i change Riser B - DIMM 1 and Riser B - DIMM 2 to any other position it looks like this:

    Riser A - DIMM 1 - OK
    Riser A - DIMM 2 - OK
    Riser A - DIMM 3 - empty
    Riser A - DIMM 4 - empty

    Riser B - DIMM 1 - OK
    Riser B - DIMM 2 - OK
    Riser B - DIMM 3 - OK
    Riser B - DIMM 4 - OK

    (only for example!!! I could try every position)

    Maybe your' right to buy new RAM-Modules with 4x 2GB ... ;-)

    but thanks for your answer
  6. ianthor7 macrumors newbie

    Feb 10, 2012
    I'm having the same issue

    I have the same computer and I'm trying to max out the RAM. Were you able to discover a solution to this issue?

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