Ram not recognized

Discussion in 'Mac Pro' started by gslrider, Apr 13, 2018.

  1. gslrider macrumors 6502

    gslrider

    Joined:
    Nov 4, 2005
    #1
    I upgraded my Mac Pro 5,1 dual CPU board (4 core 2.66), to another dual CPU board (6 core 3.46). With my old board, all 8 of my 1333 8GB DIMMS were recognized (64GB). But after upgrading the new board, only 6 of the 8 DIMMS show up (48GB). No matter how I set the DIMMS up, only 6 are recognized. All ram slots work, because I tested them by pulling 2 DIMMS out. And used the 2 remaining ones on one side, in all 4 slots. And each one was recognized. Anyone know why this is happening? Thanks.

    Please note, the newer dual board with the 6-core, wasn't originally 6-core. It was also a 4-core. But I believe it was a 2.8 instead of 2.66. The chips were just upgraded, and I swapped out the boards. Other than the Ram issue, everything has been running well.
     
  2. flowrider macrumors 603

    flowrider

    Joined:
    Nov 23, 2012
    #2
    Have you looked at the board to see if there are any red lights by the RAM slots? Have you looked at "memory" in the "System Report" to see if there is a "bad" slot?

    I have a dual CPU 5,1 and the last time I upgraded, one of my CPUs didn't register a RAM slot. When I switched CPUs, the flaw followed the CPU. So I concluded it was a bad CPU. I replaced the offending CPU and all was fine. You could have the same issue.

    Lou
     
  3. gslrider thread starter macrumors 6502

    gslrider

    Joined:
    Nov 4, 2005
    #3
    --- Post Merged, Apr 14, 2018 ---
    Thanks for the reply. I haven’t seen any red lights. No notifications of a bad slot. I’ve tested each slot, and it recognizes the ram. The problem is that it seems to only recognize 6 at a time, instead of all 8. Not sure if it’s because of the chips upgrade. Or maybe even swapping to a different board. Which confuses me, because if there is something incompatible with the new board, it shouldn’t work at all. No? Also, I’ve run a couple of ram tests, and all ram comes out clean.
     
  4. minifridge1138 macrumors 65816

    Joined:
    Jun 26, 2010
    #4
    When I did the cpu upgrade in my 4,1 I had a problem with ram not being recognized. It was caused by one of my cpus not being tight enough.

    But I have lidless cpus, the red led diagnostic lights were on, and the fan was running too fast.

    Do you still have your old board to make sure the ram is detected on it?
     
  5. gslrider thread starter macrumors 6502

    gslrider

    Joined:
    Nov 4, 2005
    #5
    I should have mentioned, that mine is a 4,1 firmware upgraded to 5,1. I don't have my old board anymore, went towards my new one. But after upgrading to 5,1, all modules were seen. Only after the board swap that only 6 of the 8, in any configuration, can be seen. No red lights. As well, the new board has upgraded CPU's as well, and they are lidless. I'm beginning to think that it's probably because the one or more of the chips isn't sitting properly. I'll have to go back to my guy for him to confirm. Thanks for the input.
     
  6. h9826790 macrumors G4

    h9826790

    Joined:
    Apr 3, 2014
    Location:
    Hong Kong
    #6
    May be you have the "wrong" DIMM spec at the very beginning (e.g. Quad rank DIMM), but luckily the old CPU tray can take them all.
     
  7. gslrider thread starter macrumors 6502

    gslrider

    Joined:
    Nov 4, 2005
    #7
    Old board took the 1333 DIMMS I had, it just dropped the speed down to 1066. And apparently, prior to the chip upgrade on the new board, all 8 DIMMS were recognized. It was only after the chip upgrade on the new board that my system started only seeing 6. I even bought 8 new DIMMS specifically for my current setup. And still, only 6 of the 8 are seen. All of the new DIMMS work. Friend tested them out on his Mac Pro 5,1 (stock dual processors).
     
  8. h9826790 macrumors G4

    h9826790

    Joined:
    Apr 3, 2014
    Location:
    Hong Kong
    #8
    Not sure able the new DIMM, but old DIMM auto down clock actually fit "wrong spec". Can you make sure the DIMM (both old and new) are all 2Rx4? If not, most likely that's the issue.

    Hard to tell why some board and take it some board cannot.

    I never realise this may happen. But all make sense now.

    Because in the last few years. I saw both, someone said that they cMP can't boot with 4Rx4 DIMM installed in all slot. But some other says that's OK, just down will run at lower speed.

    And it seems you are the 1st person to experience both, and figure out that CPU tray may make the difference.
     
  9. minifridge1138 macrumors 65816

    Joined:
    Jun 26, 2010
    #9
    My hunch is that your CPUs are not tight enough (or were over tightened and something is bent).

    Your friend has a Mac Pro 5,1. Is it a real 5,1 or a flashed 4,1?
     
  10. gslrider thread starter macrumors 6502

    gslrider

    Joined:
    Nov 4, 2005
    #10
    It's flashed as well. Which is why we couldn't figure out why all the modules were recognized on his, and not mine. But more and more, I think you may be right about the seating of the chips. Loose or too tight. We've made that assumption as well, but he thought it was more likely bad ram. He's an IT guy btw. I'm tech savvy enough to fix my own computer issues, but more complicated issues, he's the guy I go to. Also, considering, my system has crashed a number of times during intensive rendering. (eg. rendering graphic heavy files in C4D or AE).
     
  11. minifridge1138 macrumors 65816

    Joined:
    Jun 26, 2010
    #11
    If you both have 4,1 flashed to 5,1, then you can swap the entire daughter board.

    Put your board and ram into his Mac. See how much ram there is. If it sees everything, then the problem isn't the board, cpus, or ram.
    Put your ram into his board and put his board into your Mac. See how much ram there is. If it sees everything, then the problem is your board.
    Etc...
     
  12. gslrider, Apr 18, 2018
    Last edited: Apr 19, 2018

    gslrider thread starter macrumors 6502

    gslrider

    Joined:
    Nov 4, 2005
    #12
    Old DIMMS I believe are 2Rx4, I'll double check when I get home, and get back to you. The new DIMMS are 2Rx4. Your observation makes sense, but at the same time it doesn't. Why does some boards take and others don't. That's the million dollar question.

    But I'm beginning to believe minifridge is on the right track. Won't be able to confirm till my buddy gets back from vacation in a couple of weeks. Just glad he gave me a loaner to use till then.

    Update 4-19-18: Old DIMMS are 2Rx4 as well.
     

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