Mac Pro 12 Core (2010) Memory question

Discussion in 'Mac Pro' started by ndirector, Dec 2, 2011.

  1. ndirector macrumors newbie

    Joined:
    Sep 2, 2010
    #1
    Hello everyone.

    Last year I bought the 12 core machine with 12GB of RAM installed. I just recently bought 2x 4GB (Kingston). I installed both as instructed by the mac os tool on the suggested slots. Everything is fine except it's now running at 1066Mhz, before it was 1333Mhz.

    Is this significant? Am I doing anything wrong? Should it be at 1333Mhz?

    Thank you
     
  2. Zwhaler macrumors 603

    Zwhaler

    Joined:
    Jun 10, 2006
    #2
    Sounds like your sticks from Kingston are 1066MHz. The lowest speed in any one module will bring the rest down to that speed.
     
  3. ndirector thread starter macrumors newbie

    Joined:
    Sep 2, 2010
    #3
    Hello

    Thanks for the input. I just double checked the package.
    It says on the box

    "Compatible 1333mhz (PC3 10600) and 1066MHz (PC3 8500)"

    What you say makes perfect sense tho.
     
  4. Zwhaler macrumors 603

    Zwhaler

    Joined:
    Jun 10, 2006
    #4
    Does the box say that the sticks are specifically 1333MHz or 1066? Because 1333MHz sticks are compatible with 1066MHz, and 1066MHz sticks are compatible with your Mac Pro at 1333MHz it'll just slow the rest down; Another way to check is by taking out the rest of the RAM and leaving in the aftermarket modules and seeing what speed comes up. If they are 1333MHz it shouldn't bring the whole speed down to 1066MHz, I put in aftermarket 1333MHz sticks in my Mac Pro and all 8 modules are at that speed.
     
  5. ndirector thread starter macrumors newbie

    Joined:
    Sep 2, 2010
    #5
    The box only has the info I mentioned.

    I will give that a try, I'll take out all the original sticks and leave in the new ones, see what happens.

    I'll post the result.

    Thanks again

    ----------

    Hey

    I just tried what you said and now it's registering at 1333MHz (only new sticks running) so it's definitely not the new sticks. Do you think it might be a matter of slot choices? I followed the suggested installation as it popped up the first time I installed the memory.

    Any ideas?

    Thanks again
     
  6. Zwhaler macrumors 603

    Zwhaler

    Joined:
    Jun 10, 2006
    #6
    I don't think the slot choices affect it because I went through the same process and it didn't mess with my RAM speed after trying different configs. You might have to do some investigating and see if one module triggers the downclock, also if you remember that your original 12GB was at 1333MHz then something is fishy if adding the extra 2 1333MHz modules is bringing down the clock speed which shouldn't be happening.

    Next step is to click on the Apple in the upper left, "About This Mac", More Info, then click on Memory and check the breakdown of Modules and see what it tells you with all the RAM sticks back in.

    ----------

    [​IMG]
     
  7. ndirector thread starter macrumors newbie

    Joined:
    Sep 2, 2010
    #7
    Hey

    It reads "Your mac contains 8 memory slots, each of which accepts a 1066 Mhz DDR3 memory module." (before adding any memory it would say 1333MHz) :confused:

    The config is as follows

    4 4
    2 2
    2 2
    2 2

    ----------

    forget my last reply I didn't go to the right place.

    ----------

    Ok just checked. What pops out is that new sticks are not ECC, the original sticks all say DDR3 ECC the new ones just say DDR3.

    Could this be the problem?

    And thank you for your patience btw and forgive my ignorance.
     
  8. Zwhaler macrumors 603

    Zwhaler

    Joined:
    Jun 10, 2006
    #8
    That definitely would affect your memory configuration, mixing ECC with non-ECC will change the rest of your RAM to non ECC and it also sounds like that might cause the change in clock speed. If that doesn't bother you, just keep it, however on a 12 core workstation it will help to have your system run in error correction code mode and also at the higher clock speed (about 5-10% faster than 1066MHz for RAM performance)
     
  9. ndirector thread starter macrumors newbie

    Joined:
    Sep 2, 2010
    #9
    I suppose that is it then.

    I'll just replace these with ECC ones. That should fix it I suppose.

    Thanks again for all the help. :)
     
  10. Zwhaler macrumors 603

    Zwhaler

    Joined:
    Jun 10, 2006
    #10
    Your welcome, that should fix it, make sure to order 1333MHz PC 10600 ECC (if you have to choose between registered ECC or unregistered ECC, unregistered is fine) you know what to do. PS enjoy your 12 core it screams when loaded up with RAM !
     
  11. Umbongo macrumors 601

    Umbongo

    Joined:
    Sep 14, 2006
    Location:
    England
    #11
    You can't mix unregistered and registered memory, so ndirector you need to make sure you are getting DDR3 PC3-10600 ECC unbuffered DIMMs.
     

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