Mac Pro 5,1 weird RAM issue

Discussion in 'Mac Pro' started by pastrychef, Jun 4, 2013.

  1. pastrychef, Jun 4, 2013
    Last edited: Jun 5, 2013

    pastrychef macrumors 601

    pastrychef

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    #1
    I have a Mac Pro 5,1 with a pair 8GB sticks of RAM (16GB total). I decided to add another pair of 8GB sticks. When I installed the RAM in slots 1, 2, 5, and 6, the red light for slot 6 on the riser card lit up and the system only saw 24GB total.

    When I installed the RAM in slots 1, 2, 3, and 5, all 32GB was seen and no red lights.

    When I installed the RAM in slots 1, 3, 5, and 7, all 32GB was see and no red lights.

    When I installed six 1GB sticks in slots 1, 2, 3, 5, 6, and 7, all 6GB was seen and no red lights.

    When I Installed four 1GB sticks in slots 1, 2, 5, and 6, all 4GB was seen and no red lights.

    Is this behavior normal? Have any other Mac Pro 4,1 or 5,1 users experienced this? Thanks.
     

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  2. cal6n macrumors 68000

    cal6n

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    #2
    I believe the problem is usually associated with incorrectly fitted processor upgrades. Is your Mac Pro stock or upgraded?
     
  3. pastrychef thread starter macrumors 601

    pastrychef

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    #3
    Upgraded. Thanks for the info. I'll try redoing the upgrade now.
     
  4. pastrychef thread starter macrumors 601

    pastrychef

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  5. El Awesome macrumors 6502

    El Awesome

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    #5
    Did you check for bent pins?
    Could be a chipset "issue". Had such problem once on my hackintosh, the reason was a bent pin (thank god it was an easy one to fix)
     
  6. pastrychef thread starter macrumors 601

    pastrychef

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  7. El Awesome macrumors 6502

    El Awesome

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    #7
    Exactly. Can happen really fast..
     
  8. pastrychef thread starter macrumors 601

    pastrychef

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    #8
    Thanks for the info. I will check when I have a bit more time.
     
  9. pastrychef thread starter macrumors 601

    pastrychef

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    #9
    I checked all the pins with a magnifying glass and all looked good. I also swapped the position of the two CPUs. Nothing changed. All symptoms remain the same.

    The oddest part is that when I try with 1GB sticks of RAM, everything works as it should.
     
  10. cal6n macrumors 68000

    cal6n

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    #10
    What part no. (and stepping) processors did you use?
     
  11. pastrychef thread starter macrumors 601

    pastrychef

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  12. cal6n macrumors 68000

    cal6n

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    #12
    And was your donor Mac Pro a 4,1 or 5,1 originally?
     
  13. pastrychef thread starter macrumors 601

    pastrychef

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  14. cal6n macrumors 68000

    cal6n

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    #14
    That might be your problem.

    I may be wrong, but I thought that the 5,1 dual would only take the later westmere 56XX processors.

    It's mentioned (but not explained) in the first post of this thread.

    What were your original processor numbers?
     
  15. pastrychef thread starter macrumors 601

    pastrychef

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    #15
    Originals were E5420s. My assumption was that since 4,1 models could be upgraded to 5,1 models with a firmware flash and were able to run X5570s fine, a machine that started off as a 5,1 would not have problems either. Again, this was just my assumption and I could be way off the mark and totally wrong...
     
  16. cal6n macrumors 68000

    cal6n

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    #16
    Are you sure? E5420 is a Mac Pro 3,1 processor, as I recall. Do you mean E5620s? They're listed for 2010.
     
  17. pastrychef thread starter macrumors 601

    pastrychef

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  18. cal6n macrumors 68000

    cal6n

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    #18
    Yeah, that's what I thought.

    Anyway, it's not an unreasonable assumption that you've made but it may not be true, unfortunately. If you've still got your 5620s, you could try swapping them in with your new RAM to help zero in on your problem.

    I suspect you'll need the later processors for your machine to avoid glitches, though.

    Here's a list of the whole family.
     
  19. pastrychef thread starter macrumors 601

    pastrychef

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    #19
    Unfortunately, the original CPUs are long gone. I sold them after installing the X5570s and ended up profiting from the upgrade.

    I am beginning to suspect the RAM modules that I have installed. I have four sticks of these Kingstons.

    I think I've exhausted all reasonable testing measures and I think I will just leave well enough alone for now. Thanks for all the help.
     
  20. jsanford macrumors newbie

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    Aug 26, 2013
    #20
    did you ever find an answer to this issue?

    Did you ever find an answer to this? I am experiencing the same thing.
     

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