Wacky display problem on cMP 5,1. HELP!

Discussion in 'Mac Pro' started by ZombiePhysicist, Jul 10, 2016.

  1. ZombiePhysicist macrumors 6502


    May 22, 2014
    Hoping someone here can help me diagnose the problem with my 12 core 3.46Ghz, 128GB@1333MHz classic Mac Pro 5,1.

    It is hooked up to six (6) 30" cinema displays via a VisionTek 7870 through 6 mini display ports https://www.amazon.com/VisionTek-Ra...F8&qid=1468148590&sr=8-2&keywords=eyefinity+6. No boot screen, but the system has been rock solid working just fine for the last 9 months or so.

    The system never sleeps (just the screens dim) and is on 24/7. And the other day, I go to wake the screens and they wont go on. Some are black and off. Some are trying to cycle on and flicker and image and go off. I figure no big deal, it bombed for some reason . Reboot. Same thing.

    After much dickering, I realize that the card now can only drive 3 of the 6 screens. But weirdly it can drive any 3 of the monitors (so we know they all still work) in any of the ports (so none of the ports are bad) so long as it's not running more than 3 at a time.

    So now I figure, the card must have went bad, and order a new card, and when I install it. Same exact thing.

    So now I'm just baffled. I'm wondering, could the power supply somehow be going and not feeding enough juice to the 7870 graphics card, so it can drive only 3 monitors? Could something have blown (a capacitor) on the motherboard?

    Right now I'm checking to see if I can throw 2 cards driving 3 monitors each in as a temporary solution, but I need this machine for work until apple releases a new mac pro of some kind.

    Any thoughts on what it can be, or what I should try to further diagnose the problem?
  2. edanuff macrumors 6502

    Oct 30, 2008
    How are you connecting those displays? Doesn't the 30" Cinema use Dual-link DVI? Could be an issue with whatever adapters you're using.
  3. ZombiePhysicist thread starter macrumors 6502


    May 22, 2014
    They are using the apple dual link adapters. They seem to be fine. They were working just fine for the last 6 years, so I'm doubting anything changed with them. Things just spontaneously stopped working. I'm totally stumped. Never even heard of anything like this happening. So wacky.
  4. edanuff macrumors 6502

    Oct 30, 2008
    Where are they plugged in? Every one of those has as USB power supply. If that went bad, then they'd stop working.
  5. ZombiePhysicist thread starter macrumors 6502


    May 22, 2014
    The USB ports are plugged into a 7 port hub. If they went out, then you're right, they go dark. But any of the 6 work fine, just as long as I only plug any 3 of them at one time. So the USB part work.
  6. ColdCase macrumors 68030

    Feb 10, 2008
    So you haven't updated the OS or any software recently? The cables are OK?

    I think I've read here about something similar awhile ago. And I don't recall the solution. Hope you get things sorted out soon.
  7. ZombiePhysicist thread starter macrumors 6502


    May 22, 2014
    No change. This actually happened while I was away from the computer.

    Meaning, I leave the machine on 24/7. Screens dim (but CPU never goes to sleep). I come back an hour later and its just gone bonkers. Reboots, new video cards, but the problem persists.

    My guess is one of 2 things?

    1) The cMP power supply is starting to weaken, and perhaps the draw the card was getting is no longer sufficient?

    2) Some capacitor or something on the cMP is going? This one makes less sense but, I'm so at a loss with this. Just freak show weird.
  8. ActionableMango macrumors G3


    Sep 21, 2010
    As a matter of troubleshooting, I would rule out software/corruption/settings/etc by installing a fresh copy of OS X on a spare drive to see what happens. If that doesn't work, then the problem points to hardware. If it does work, then the problem points to software, settings, or some other cruft that happened along the way.

    Unfortunately you probably know more than anyone else here about running so many monitors.

    User jkheit did 10 monitors here but he hasn't been around in a long time.

    MacVidCards has probably done more than 3 monitors too, but he's not allowed to be here. Maybe you could ask over on Netkas forums.
  9. ZombiePhysicist thread starter macrumors 6502


    May 22, 2014
    Wow, why is macvidcards not allowed on here? He's super valuable member of the community. That's totally nuts.

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