Mini displayport curiosity

Discussion in 'Mac Pro' started by jhall1jax, Feb 27, 2017.

  1. jhall1jax macrumors newbie

    Joined:
    Sep 2, 2006
    #1
    Just traded my 2012 rMPB with my buddy's 2010 5,1 Mac Pro 12x2.66 with the 5870 card. He's used it for years with the old Apple 30" monitor which used a (dual-link) DVI. He's never used the minidisplay ports.

    I initially had the Mac Pro hooked up to a cheapo 1920x1080 monitor via DVI for a few days. I have 2 2560x1440 monitor that have displayport connectors. Using two mini displayport to displayport cables, I plugged them in and they work great at the native resolution. I disconnect the DVI monitor and put it away.

    Everything was fine until I slept the Mac Pro, then woke it the next day - I hear it click on and the fans spin up, but no video. I rebooted, no boot. I disconnected one monitor, and plugged the other in to the DVI port (instead of the DP port) - still no boot.

    The only way I could get it to boot was to get out the first 1920x1080 monitor I used via DVI - then it boots fine. After more testing, it looks like I cannot get it to wake when ANY monitor is plugged into one of the mini DP ports.

    I swapped out the motherboard CMOS/NVRAM battery (and thereby reseated the 5870), reset SMC and PRAM. No effect.

    Anyone else have this issue? Very weird.

    On another note, I heard that the "stock" Apple 5870 uses a single 6-pin power connector. Mine is a double 6-pin, and isn't branded Apple anywhere. I'm assuming this is the Apple-supplied 5870 but I'm not 100% sure.

    Jason
     
  2. ActionableMango, Feb 27, 2017
    Last edited: Feb 27, 2017

    ActionableMango macrumors 604

    ActionableMango

    Joined:
    Sep 21, 2010
    #2
    Non-compliant DP and mDP cables are fairly common and can pass through 3.3v on pin 20 which can either damage equipment or prevent a computer from POSTing. This matches your experience perfectly, so I suspect the cables.

    The Apple 5870 uses two 6-pin connectors. Maybe you are thinking of the Apple 5770, which uses one.
     
  3. jhall1jax thread starter macrumors newbie

    Joined:
    Sep 2, 2006
    #3
    Interesting and thanks for the reply - the ones I bought appear to be appropriate cables (they are v1.2 cables):

    https://www.amazon.com/gp/product/B00C7RJQPY/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1

    Same behavior when using the DVI connection to one monitor, along with a good-quality active miniDP-to-HDMI converter feeding an HDMI connector to another monitor. The computer just doesn't seem to like anything plugged into a miniDP port when booting or waking. I've been building PCs and using Macs since the early 90's; haven't quite run across this issue before.

    Edit: spelling
     
  4. ActionableMango macrumors 604

    ActionableMango

    Joined:
    Sep 21, 2010
    #4
    There are two reviewers who specifically say that it passes through power on pin 20, which is exactly the problem I was concerned about. If you want to read more about this:
    https://hardforum.com/threads/displayport-cables-must-not-use-pin-20-warning.1803684/
     
  5. jhall1jax thread starter macrumors newbie

    Joined:
    Sep 2, 2006
    #5
    Wow, great catch! Thank you for checking on that. I'll see if I can return those two cables and get cables (like the below) that are confirmed pin 20 disconnect.

    https://www.amazon.com/Accell-B143B...&sr=8-1&keywords=accell+mini+displayport&th=1
     
  6. ActionableMango macrumors 604

    ActionableMango

    Joined:
    Sep 21, 2010
    #6
    What worries me is that you are seeing the same problem with the MDP-HDMI adapter. So either the out of spec cables are not the problem, or the damage is already done.
     
  7. jhall1jax thread starter macrumors newbie

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    Sep 2, 2006
    #7
    I'll report back when the "in-compliance" cables arrive tomorrow.
     
  8. jhall1jax thread starter macrumors newbie

    Joined:
    Sep 2, 2006
    #8
    The new cables work perfectly. No issues with waking or booting any more. Thanks again.

    Jason
     

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