GTX 680 and LG 4K monitor -> no 60Hz?

Discussion in 'Mac Pro' started by mumux, Dec 16, 2018.

  1. mumux macrumors newbie

    mumux

    Joined:
    May 4, 2015
    #1
    Hello,

    So I have this new 4K monitor, the LG 27UK650, a nice monitor, but I'm not able to make it work at 60Hz.
    The Mac Pro is a 3.1 with an Asus GTX 680 2Gb that I flashed months ago with the help of this post:
    https://forums.macrumors.com/thread...-pci-e-2-0-5gt-s.1603260/page-4#post-17832428

    The problem I'm experiencing is that if I set the monitor Displayport to 1.2 the Mac does not boot at all.
    If Displayport 1.2 is disabled (working at 1.1 I guess) the Mac boots and of course I only get 30Hz.

    I tried SwitchResX but 1080p @ 60Hz is not HiDPI (because of the Displayport setting).

    Since both the GTX 680 and the monitor are supposed to work at 60Hz, what am I doing wrong?
    Should I send the monitor back?

    Thank you
     
  2. Fooze macrumors member

    Joined:
    Mar 1, 2016
    #2
    This might be a long shot, but have you tried any other display port cables? Maybe your cable is limiting the bandwidth.
     
  3. mumux thread starter macrumors newbie

    mumux

    Joined:
    May 4, 2015
    #3
    The cable I used is the one included with the 4K monitor so I guess it should't be the culprit.
     
  4. Fooze macrumors member

    Joined:
    Mar 1, 2016
    #4
    That setup should work. I have an evga gtx680 and it’s working with a Dell 4k display.

    By any chance do you have a Windows install you can boot into? See if it works there and then you’ll know it’s software issue and not hardware related.
     
  5. mumux thread starter macrumors newbie

    mumux

    Joined:
    May 4, 2015
    #5
    I don't have a bootcamp install, just parallels, but I had the chance to try a friend's GTX 680 (MSI not flashed) and it worked fine at 60Hz.
    No bootscreen until black screen with white apple (it's a High Sierra unsupported install) but I guess this is expected.

    Then the cuprit seems to be the Mac ROM, any thoughts on that?

    Thank you
     
  6. ActionableMango macrumors G3

    ActionableMango

    Joined:
    Sep 21, 2010
    #6
    The main benefit of the MacEFI is boot screens. However, there's no way to get 4K boot screen out of a GTX 680 anyway, flashed or not. So you might as well restore your original firmware if that fixes your other problem.
     
  7. mumux thread starter macrumors newbie

    mumux

    Joined:
    May 4, 2015
    #7
    4K boot screen worked @ 30Hz in my card.
    In normal operation, with a correctly working MacEFI, I would use 60Hz, but if I need boot screen, I could just set the monitor to DP 1.1 and reboot!

    That's why I'd rather try to make it work correctly than look for a 2ᴺᴰ card with boot screen.
     

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6 December 16, 2018