RAM check for cMP 4,1/5,1

Discussion in 'Mac Pro' started by owbp, Dec 8, 2016.

  1. owbp macrumors 6502a

    owbp

    Joined:
    Jan 28, 2016
    Location:
    Belgrade, Serbia
    #1
    Found these two sticks on local ads for cheap, at least I think so (45€ for both), but I would like to check if they're ok for the 2009 cMP?
    The only thing i know for sure is that they're 1066 MHz, but that's obvious :(
    IMG_0004.jpg IMG_0005.jpg IMG_0006.jpg
    Is there any big performance drawback in using 1066 vs 1333 MHz ram after upgrading CPU?
     
  2. CapnDavey macrumors 6502

    CapnDavey

    Joined:
    Apr 11, 2015
    #2
    they will work but don't mix them with the OEM Udimm ram
     
  3. h9826790 macrumors 604

    h9826790

    Joined:
    Apr 3, 2014
    Location:
    Hong Kong
    #3
    It should work in the cMP. Since it's a 4Rx4 RAM stick, you may not able to run 4 of them without issue, but 2 of them should not be a problem.
     
  4. owbp thread starter macrumors 6502a

    owbp

    Joined:
    Jan 28, 2016
    Location:
    Belgrade, Serbia
    #4
    Thank you for such quick and detailed responses.
    So if I am planning to have 48gb of ram (3 sticks) it would be wiser to skip this?
     
  5. h9826790 macrumors 604

    h9826790

    Joined:
    Apr 3, 2014
    Location:
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    #5
    I am not sure how many 4Rx4 sticks the cMP can handle. However, what I know is 2Rx4 is the good working spec.

    May be the cMP can still work with 3x16G 4Rx4 stick without issue. If that's really cheap, and that's what you want / need now. May be OK to take the risk.

    There was a post about some users can't get the RAM run at correct speed. And end up the theory that seems can fit in all cases is about the memory rank. e.g. If install all 4 sticks, the memory will not able to maintain at 1333MHz but automatically drop to 1066MHz.

    So, I think the cMP can handle 3x those 16GB stick, and in worst case may be speed drop below 1066MHz. So far, this speed drop seems only happen when all 4 sticks are installed. But since lack of proper tests, hard to know the real limitation.
     
  6. HAL2010 macrumors member

    HAL2010

    Joined:
    Nov 3, 2014
    Location:
    The Netherlands
    #6
    I have a somewhat similar question. I applied the firmware update (4,1 to 5,1) to a 8 core 2,26GHz Mac Pro 4,1. Now I want to upgrade the memory from 8 x 1GB to 4 x 8GB. I use DDR3 ECC Registered HMT31GR7BFR4C-H9 modules from Hynix. I read somewhere that they will work. It's 32GB in total, but all I see is 24GB. I used all kinds of combinations and I also consulted the manual. The most I can get out of 4 x 8GB is 24GB. I know all connectors are good because my old memory works in all 8 connectors. I also know that all 8GB modules work because I mixed them up.

    Is this a 1066MHz versus 1333MHz issue? So do I need to update my processors in order to make the memory work?
     

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  7. h9826790 macrumors 604

    h9826790

    Joined:
    Apr 3, 2014
    Location:
    Hong Kong
    #7
    It should be relatively easy to fine out which stick / slot is not working.

    Just install the RAM in slot 1,2,5,6 and then open the about my Mac -> memory page to see which one is not working. My mac only has 4 slots, no the same as yours, but you should able to clearly see which slot is "empty".
    Screen Shot 2017-01-23 at 16.22.11.jpg
     
  8. HAL2010 macrumors member

    HAL2010

    Joined:
    Nov 3, 2014
    Location:
    The Netherlands
    #8
    I did that several times. I can't seem to find a pattern. By mixing everyting up I have discovered that all sticks work and all slots are good. But I am stuck with 24GB in stead of 32.
     
  9. h9826790 macrumors 604

    h9826790

    Joined:
    Apr 3, 2014
    Location:
    Hong Kong
    #9
    So, now assume you name your sticks ABCD.

    You can boot with only stick A in slot 1 and stick B in slot 5 (only 16GB RAM).

    And you can also boot with only stick C in slot 1 and stick D in slot 5 (also only 16GB RAM)?

    If this is true, then I agree that all 4 sticks are working fine.
     
  10. HAL2010 macrumors member

    HAL2010

    Joined:
    Nov 3, 2014
    Location:
    The Netherlands
    #10
    I'm going to do something like that. Figure out a method so I can check everything. Thanks!
     

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