RAM suddenly not recognized on Mac Pro

Discussion in 'Mac Pro' started by dnocuz, Jan 22, 2016.

  1. dnocuz macrumors newbie

    Jan 22, 2016

    I have a 2008 Mac Pro 3.1 2 x 2.8 Quad Core running OSX 10.8.5 with 8 GB 800 MHz DDR2 FB-DIMM. Recently my system has been a little sluggish and to make a long story short, I realized that the system profiler was showing only 4GB of RAM instead of the 8GB of RAM that came with the computer when I originally bought it. The configuration is 2 x 2GB cards in riser A and 2 x 2GB cards in riser B. After doing some troubleshooting it seems as though the 2 RAM cards in riser B are the problem. The riser itself seems to be fine. I've run tests using Apple Hardware Test and Rember, both finding no problems - but both could not see the bad RAM to begin with. I'm just wondering why the RAM has all of the sudden stopped working. Is it something that can be fixed or does the RAM need to be replaced?


  2. MacVidCards Suspended

    Nov 17, 2008
    Hollywood, CA
    Swap and switch to narrow it down.

    Probably a single bad stick.

    Things break, even electronics.
  3. dnocuz thread starter macrumors newbie

    Jan 22, 2016
    I tried swapping the pair - no luck. I'll try swaping the single sticks.
  4. pastrychef macrumors 601


    Sep 15, 2006
    New York City, NY
    On my old 3,1, it would stop recognizing RAM whenever I took out the daughter cards. I had to reseat them, boot up to see if RAM was recognized, and repeat if not. It would sometimes take dozens of attempts but once recognized, it would continue to work until I pulled out the daughter cards again.
  5. dnocuz thread starter macrumors newbie

    Jan 22, 2016
    Yes, you're absolutely right. Through a bit of trial and error I figured out that one of my RAM sticks is bad. It's the only one that causes the riser's red light to come on. Since the RAM needs to be installed in pairs, the Mac Pro was only reading 2 of the 3 good sticks. Looks like I'll be buying more RAM.



Share This Page