nMP + 10.13.5 + HDMI = no stable sync?

Discussion in 'Mac Pro' started by damezumari, Jun 13, 2018.

  1. damezumari macrumors member

    Joined:
    Dec 6, 2014
    #1
    I have used my nMP (D500, 32GB) for few years with various issues every now and then; notably resume from standby crashes GPU so I don't. Currently I use two displays, Acer HK321 and Dell UP3214Q (both 4k).

    With 10.13.5 there seems to be a new interesting issue; if I connect one of my displays via HDMI (and I should, as there is no 4k output over thunderbolt in login screen?), the screen goes black every few seconds, and sometimes re-syncs again and sometimes now. This makes that display unusable via HDMI.

    Same display is still fine over thunderbolt (aka mini displayport), and the behavior started with 10.13.5, so I suspect that is the culprit. I guess I will have to try the HDMI cable with different computer to be sure, but I am very surprised if it broke down just as I upgraded to 10.13.5.

    I wonder if I should just downgrade the AMD drivers or revert to a TM backup, this is somewhat .. annoying.
     
  2. axantas macrumors regular

    axantas

    Joined:
    Jun 29, 2015
    Location:
    Home
    #2
    They did indeed remove the 4K output during startup - so no bootlogo, no possibility to visibly select the startvolume. BUT, this came back with a system update a couple of month ago. There were one or two Firmware Updates. Maybe you should try to "iron over" a combo-update for your nMP.
    >> just let it run. As you are "blindfolded", you will just sit in front of a black screen and see your Mac reboot several times. It will take quite some time. Do not interrupt it! (or connect the not really working HDMI monitor for this procedure.)
     
  3. mikeboss macrumors 65816

    mikeboss

    Joined:
    Aug 13, 2009
    Location:
    switzerland
    #3
    I'm running an EIZO (1900x1200) off the HDMI port on my MacPro6,1 and I don't see the symptoms you're describing with macOS 10.13.5.
     
  4. axantas macrumors regular

    axantas

    Joined:
    Jun 29, 2015
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    #4
    The flickering symptoms once existed indeed - I guess it was brand specific DELL particularly, in MacOS AND Bootcamp. One could avoid it by forcing the monitor to use 50Hz - which is quite a hassle.
    I don't know how and when, but It was eliminated after quite some time.
     
  5. damezumari thread starter macrumors member

    Joined:
    Dec 6, 2014
    #5
    It turns out it was probably false alarm (loose cable?), it seems that once I rebooted (thanks to it deciding not to fire up displays at all today after a day of not being used) and reconnected cables HDMI is once more fine. Still no picture on displayport-based 4k/60hz monitor setup at boot so second monitor at end of 30hz HDMI is helpful. I wonder if combo update would fix it..
     
  6. damezumari thread starter macrumors member

    Joined:
    Dec 6, 2014
    #6
    I was being optimistic; I restarted machine yesterday, this morning HDMI connected display is again going on and off every few seconds. Sigh.. I guess I will be using time machine to try previous version next when I have to motivation (for now, just using one display).
     

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