how to set correct resolution on thunderbolt 3 port

[Marco Fioretti]

Hello all, again.

As you may already know from my previous threads, last week I
installed Ubuntu 21.04 on a DILC Nuc "10th gen i5-10210U 4.20 ghz Ram
16gb, M2 Ssd 256 gb" without problems, except connecting the monitor
to a digital port.

The NUC has HDMI and Thunderbolt 3 ports. The monitor has optimal
resolution 1680x1050 @60Hz, a VGA port and a DVI one. If I use a VGA
cable plus an HDMI to VGA adapter Ubuntu lists the optimal resolution
and I can set it. If I use a "Thunderbolt 3 to DVI" cable, it does
work, but Ubuntu does NOT lists that same resolution, so I cannot set
it. The closest it lists is 1600xsomething.

I had almost the same problem with the previous computer (Ubuntu 20.04
LTS) that had VGA and HDMI outputs, and the same monitor. Back then, I
had solved it with these two commands:

xrandr --newmode "1680x1050_60.00" 147.14 1680 1784 1968 2256 1050
1051 1054 1087 -hsync +vsync

xrandr --addmode HDMI-0 1680x1050_60.00

Current output of xrandr is pasted below. My question is if the same
commands would work by only changing "HDMI-0" to (I guess) "DP-2", or
how to change them for a thunderbolt port, before/ without risking
damages to the monitor, which I really cannot afford right now...

Before posting I did check online (*) and the xrandr man page,
but I have not found or recognized relevant information for this
specific case.

TIA,
	Marco

######################################################################

#> xrandr
Screen 0: minimum 320 x 200, current 1680 x 1050, maximum 16384 x 16384
DP-1 connected primary 1680x1050+0+0 (normal left inverted right x axis y axis) 474mm x 296mm
   1920x1080     60.00 +  59.94  
   1680x1050     59.88* 
   1280x1024     75.02    60.02  
   1280x960      60.00  
   1152x864      75.00  
   1280x720      60.00    59.94  
   1024x768      75.03    70.07    60.00  
   832x624       74.55  
   800x600       72.19    75.00    60.32    56.25  
   720x480       60.00    59.94  
   640x480       75.00    72.81    66.67    60.00    59.94  
   720x400       70.08  
DP-2 disconnected (normal left inverted right x axis y axis)
HDMI-1 disconnected (normal left inverted right x axis y axis)

######################################################################

(*) e.g.:

https://www.codegrepper.com/code-examples/shell/setting+the+resolution+in+ubuntu+20

https://unix.stackexchange.com/questions/486350/using-displayport-over-usb-c-thunderbolt-3-to-drive-external-5120x2160-monitor





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