Blinking (replaced 24'' FHD with 27'' 4k)

User Support Hardware Issues
1

I was running a 3 FHD (each 1920x1080) Monitor setup for years with Qubes 4.0.3 and a RX480 8GB.

My new Dell U2720Q has Native Resolution : 4K 3840 x 2160 at 60 Hz
Replaced one of the FHD Monitors who was also running via Display Port, i can see 4k Resolution at 60Hz but Monitor keeps going on and off very very often.

I did try,

qvm-features dom0 gui-videoram-min $(($WIDTH * $HEIGHT * 4 / 1024))
qvm-features dom0 gui-videoram-overhead 0

qvm-features dom0 gui-videoram-min 64800
qvm-features dom0 gui-videoram-overhead 0

but 4k kept blinking after reboot.
I also tried putting some into overhead, though it did not change anything, wiki is kinda vague from a novice standpoint.

Switched to FHD Resolution the Blinking Stopped but it is kinda blurry, that was yesterday night.
Decided to look later into solution, had to do some work on Qubes PC first, now after 4h of sitting in front of it and right when i had the time to look into this Display problem the new 4k Dell started randomly blinking even though it was on FHD.

My current guess is to look into the DP cable and replace it to get 4k running.

Ideas?

2 
Screen 0: minimum 320 x 200, current 5760 x 1080, maximum 16384 x 16384
DP-1 connected 1920x1080+1920+0 (normal left inverted right x axis y axis) 597mm x 336mm
   3840x2160     60.00 +  29.56  
   2560x1440     59.95  
   2048x1536     75.00    60.00  
   1920x1440     75.00    60.00  
   2048x1280     59.92  
   1856x1392     75.00    60.01  
   1792x1344     75.00    60.01  
   2048x1152     60.00  
   1920x1200     59.88  
   1920x1080     60.00*   60.00    50.00    59.94    24.00    23.98  
   1600x1200     75.00    70.00    65.00    60.00  
   1680x1050     59.95  
   1400x1050     74.76    59.98  
   1280x1024     75.02    60.02  
   1440x900      60.00  
   1280x960      60.00  
   1280x800      59.81  
   1152x864      75.00  
   1280x720      60.00    50.00    59.94  
   1024x768      75.05    60.04    75.03    70.07    60.00  
   960x720       75.00    60.00  
   928x696       75.00    60.05  
   896x672       75.05    60.01  
   832x624       74.55  
   800x600       75.00    70.00    65.00    60.00    72.19    75.00    60.32    56.25  
   720x576       50.00  
   700x525       74.76    59.98  
   720x480       60.00    59.94  
   640x512       75.02    60.02  
   640x480       60.00    75.00    72.81    75.00    60.00    59.94  
   720x400       70.08  
   576x432       75.00  
   512x384       75.03    70.07    60.00  
   416x312       74.66  
   400x300       72.19    75.12    60.32    56.34  
   320x240       72.81    75.00    60.05  
DP-2 disconnected (normal left inverted right x axis y axis)
HDMI-1 connected 1920x1080+0+0 (normal left inverted right x axis y axis) 531mm x 298mm
   1920x1080     60.00*+  50.00    59.94  
   1680x1050     59.88  
   1400x1050     74.76    59.98  
   1600x900      60.00  
   1280x1024     75.02    60.02  
   1440x900      60.00  
   1280x960      60.00  
   1280x800      59.91  
   1152x864      75.00  
   1280x720      60.00    50.00    59.94  
   1024x768      75.05    60.04    75.03    70.07    60.00  
   960x720       75.00    60.00  
   928x696       75.00    60.05  
   896x672       75.05    60.01  
   832x624       74.55  
   800x600       75.00    70.00    65.00    60.00    72.19    75.00    60.32    56.25  
   720x576       50.00  
   700x525       74.76    59.98  
   720x480       60.00    59.94  
   640x512       75.02    60.02  
   640x480       60.00    75.00    72.81    75.00    60.00    59.94  
   720x400       70.08  
   576x432       75.00  
   512x384       75.03    70.07    60.00  
   416x312       74.66  
   400x300       72.19    75.12    60.32    56.34  
   320x240       72.81    75.00    60.05  
HDMI-2 connected primary 1920x1080+3840+0 (normal left inverted right x axis y axis) 531mm x 298mm
   1920x1080     60.00*+  50.00    59.94  
   1680x1050     59.88  
   1400x1050     74.76    59.98  
   1600x900      60.00  
   1280x1024     75.02    60.02  
   1440x900      60.00  
   1280x960      60.00  
   1280x800      59.91  
   1152x864      75.00  
   1280x720      60.00    50.00    59.94  
   1024x768      75.05    60.04    75.03    70.07    60.00  
   960x720       75.00    60.00  
   928x696       75.00    60.05  
   896x672       75.05    60.01  
   832x624       74.55  
   800x600       75.00    70.00    65.00    60.00    72.19    75.00    60.32    56.25  
   720x576       50.00  
   700x525       74.76    59.98  
   720x480       60.00    59.94  
   640x512       75.02    60.02  
   640x480       60.00    75.00    72.81    75.00    60.00    59.94  
   720x400       70.08  
   576x432       75.00  
   512x384       75.03    70.07    60.00  
   416x312       74.66  
   400x300       72.19    75.12    60.32    56.34  
   320x240       72.81    75.00    60.05  
DVI-D-1 disconnected (normal left inverted right x axis y axis)
3

Replaced DP cable and 4k stopped blinking for now. Lets see if this doesn’t start in a few Hours.

4

My new Dell U2720Q has Native Resolution : 4K 3840 x 2160 at 60 Hz
Replaced one of the FHD Monitors who was also running via Display Port, i can see 4k Resolution at 60Hz but Monitor keeps going on and off very very often.

I have the first generation of that monitor. It does the same thing for
me on HDMI in Qubes (but not other OS’). Swapping it to DP stops it.

Switched to FHD Resolution the Blinking Stopped but it is kinda blurry, that was yesterday night.

Some of these monitors have crappy scaling. Even when you use an integer
multiple of the resolution, they look like crap. Better to keep trying
to get native working, otherwise, why have a 4K monitor.

1 Like
5

Seems the DP cable that come with the Monitor fixed the problem.

6

Setting

qvm-features dom0 gui-videoram-min 64800
qvm-features dom0 gui-videoram-overhead 0

didn’t work for me. Anything else to try?
No other equipment in range, 1 laptop and 1 external monitor.