Mac Pro 5,1 displays lose connection... Grfx card hosed?

Discussion in 'Mac Pro' started by fuchsdh, Sep 20, 2015.

  1. fuchsdh macrumors 6502a

    Joined:
    Jun 19, 2014
    #1
    So I've got the machine in my sig. Just returned from a vacation, and while using my Mac suddenly the displays cut out and go to sleep. The Mac itself is still awake--the displays just lost visual.

    Trying to reboot, and now the issue has become more pronounced--the video is cutting out just after the computer manages to start up again.

    I assume this means there's an issue with my 7950.
     
  2. h9826790 macrumors 604

    h9826790

    Joined:
    Apr 3, 2014
    Location:
    Hong Kong
    #2
    Do you have another GPU to test? May be the original one?
     
  3. MacVidCards Suspended

    Joined:
    Nov 17, 2008
    Location:
    Hollywood, CA
    #3
    Clean out fan with air blown backwards. But I must tell you I have a box of "spare parts" Tahiti cards. Many will boot up to a beautiful image but will "cut to black" if stress is throw at them. So you have described a standard failure mode.

    There is a guy on EBay selling defective Mac Tahiti cards as such. To get performance out of these cards AMD ran them at high clocks. (Same thing they are doing now with the "overclocker's dream" Fiji) to quote one of my fave movies "a candle that burns twice as bright burns twice as fast".

    AMD cards run too hot and burn up far more quickly then the green team ones.

    I also noticed another guy on EBay selling a repair kit. He claims that there is a MOSFET that is failure prone. I don't have time to try, but would be interesting to know if some could be fixed this way.
     
  4. fuchsdh thread starter macrumors 6502a

    Joined:
    Jun 19, 2014
    #4
    Thanks for the tip. I intend to blow out the card and entire system with air, and grab a spare Quadro from work and confirm it's the video card.

    I thought stressing the card might be the cause (and it certainly may be), but there doesn't seem to be a good correlation. In my tests yesterday it was cutting to black with no games or intensive programs open. Temps and fan speeds via iStat weren't showing anything either.
     
  5. h9826790 macrumors 604

    h9826790

    Joined:
    Apr 3, 2014
    Location:
    Hong Kong
    #5
    iStat won't show any temps or fans of the 7950, that's completely normal.
     
  6. fuchsdh thread starter macrumors 6502a

    Joined:
    Jun 19, 2014
    #6
    Oh yeah, I meant surrounding diodes and the expansion slot fans. Left my can of air at work so I'll try to clean it tomorrow. :)
     
  7. haralds macrumors 6502

    haralds

    Joined:
    Jan 3, 2014
    Location:
    Silicon Valley, CA
    #7
    What kind of connector? I would look at reseating that first.
     
  8. fuchsdh thread starter macrumors 6502a

    Joined:
    Jun 19, 2014
    #8
    My monitors are attached to the mDP ports on the 7950, but I reseated those with no issues. Wouldn't make sense for them to randomly cut out when the machine isn't moving, in any case.
     
  9. h9826790 macrumors 604

    h9826790

    Joined:
    Apr 3, 2014
    Location:
    Hong Kong
    #9
    Even the machine doesn't move. However, it's vibrating, the GPU has it's own fan, it's definitely vibrating as well. For a poor connection, those vibration may be already "big" enough to produce random cut off in signal.
     

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