Mac Pro 4,1 boot issue. Power supply failure?

Discussion in 'Mac Pro' started by troc, Sep 21, 2015.

  1. troc macrumors newbie

    Jun 26, 2006
    The Netherlands
    Hi, need a little help.

    I have a 4,1 flashed to 5,1 with a 6 core 3.36 GHz CPU, ATI 7950, Samsung SSD on a PCIe card etc. Well upgraded in other words :)

    At the weekend, I wandered into my office to discover the PSU clicking away merrily to itself obviously desperately trying to wake from sleep. Probably about one click a second from the main relay with the fans occasionally starting to spin up before a shutdown and click on again.

    The only way to stop this was to hold the power button until it switched off (or pull out the plug).

    When I try restarting, it will chime as normal followed by the usual grey screen, apple logo (ATI card is flashed) and then reboot twice before finally booting to the desktop.

    If I keep the computer on 100% and stop it from sleeping, then all seems to be fine.

    Full Spec:

    4,1 flashed to 5,1
    single CPU 6x3.46 GHz
    24GB (3x8) RAM

    ATI 7950 (PC flashed with mac rom)
    Nvidia 120 (original gfx card)
    Sonnet USB 3 card
    Sonnet SSD card (Boot SSD)

    Various generic 2 and 1TB HDs.

    I am wondering it there's too much current draw from the SSD card and 7950 which is stressing an old and failing PSU? Or does it indicate the ATI card is faulty? RAM all appears fine and nothing is showing up on the hardware tests.

    I suspect it's a failing power supply and have ordered a reconditioned one but in the meantime, does anyone think it's more likely to be something else like the ATI card?


  2. carpsafari Suspended


    Sep 13, 2015
    the Netherlands
    Have you checked the PSU for dust?
    I recently had this issue and found out when my MP crashed without warning that there was a lot of dust in there.
  3. h9826790 macrumors G4


    Apr 3, 2014
    Hong Kong
    For your config, there is no way that drawing too much from the PSU. The Tempo SSD draw almost nothing if you monitor it via iStat.

    I am running two 7950 by internal power only, with the W3690 also running in full power, still unable to reach 50% of the PSU's limit (980W).

    So, it's hard to believe that your PSU is in such bad condition any unable to provide less then 50% of it's rated power (but still working).

    The relay may be in bad condition, but not necessary the whole PSU.
  4. MacVidCards Suspended

    Nov 17, 2008
    Hollywood, CA
    Do you need both GPUs in there? I'd remove that 120, I can't imagine most people need more then the 4 displays a 7950 can run.
  5. troc thread starter macrumors newbie

    Jun 26, 2006
    The Netherlands
    So, I installed a new PSU and all appears well. No more wake from sleep or boot issues and I would also have appeared to have cured a couple of rather irritating gaming issues where my computer would pause and catch up during complex scenes or when a lot of new textures needed to load.

    Now it could be a coincidence related to having to remove all the expansion cards (and the CPU tray as a WIFI antenna wire had disconnected - not that I have WIFI switched on) and reinstall everything but all seems much happier now.

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