GTX 980 HDMI limited bandwidth

Discussion in 'Mac Pro' started by slughead, Oct 1, 2016.

  1. slughead macrumors 68040


    Apr 28, 2004
    Mac Pro 5,1
    GTX 980 (not flashed)
    OS X Sierra
    Latest Nvidia drivers

    The problem:
    When plugged into the Displayport on the monitor, everything works as expected, it goes up to the expected resolution of 3440x1440 and I think it goes up to the expected 100hz. However, if I plug the GTX980 into the HDMI port (I believe it's HDMI 1.4), it is limited to 1080p when it is supposed to be able to go to 3440x1440 @ 50hz. It not only does not show higher resolutions in Displays preference pane but also attempts to force the resolution have failed, as below

    What I've tried:
    - My PC laptop runs it at full res over HDMI
    - My Mac Laptop (macbook pro) runs at full res over HDMI
    - I used a displayport -> HDMI adapter rated at HDMI 1.4 as well as the built-in HDMI port (neither works)
    - Manually entering in the Resolution/pixel frequency/porches and such using SwitchResolutionX utility and info gathered from exporting the EDID output on the PC laptop (Oh yes, I went there)
    - Manually entering the EDID data into the OS plist on my monitor (which I believe is what SwitchResolutionX does anyway)
    - Resetting monitor settings to default
    - Holding "option" while clicking the "scaled" radio button in Displays panel

    Does anyone have any other ideas?
  2. ActionableMango macrumors G3


    Sep 21, 2010
    The Pixel Clock Patch is the only thing I can think of. It is supposed to patch in support for oddball 3440x1440 HDMI timings, which sounds exactly like your problem.

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