It’s really horrible… older and cheap (Siemens?) monitors are not compatible with newer DisplayPort -> DVI or HDMI -> DVI signals.

NO MATTER YOUR SETTINGS!

If there is no output… try a newer monitor… if there is output… you know it’s the monitor.

First i had: IIYAMA @ DVI <- HDMI (works) & SIEMENS @ DVI <- DisplayPort (no signal)

now i have: SIEMENS @ DVI <- HDMI (no signal) & IIYAMA @ DVI <- DisplayPort (works, HDMI2 = DisplayPort?)

xrandr; # shows me
Screen 0: minimum 320 x 200, current 1680 x 1050, maximum 8192 x 8192
DP1 disconnected (normal left inverted right x axis y axis)
HDMI1 connected 1680x1050+0+0 (normal left inverted right x axis y axis) 474mm x 296mm
   1680x1050     59.95*+
   1280x1024     75.02    60.02  
   1440x900      59.90  
   1280x960      60.00  
   1152x864      75.00  
   1024x768      75.08    70.07    60.00  
   832x624       74.55  
   800x600       72.19    75.00    60.32    56.25  
   640x480       75.00    72.81    66.67    60.00  
   720x400       70.08  
HDMI2 connected (normal left inverted right x axis y axis)
   1600x1200     60.00 +
   1280x1024     75.02    60.02  
   1024x768      75.08    60.00  
   800x600       75.00    60.32  
   640x480       75.00    60.00  
   720x400       70.08

xrandr --output HDMI2 --mode 1024x768; # WOHOO! WE HAVE OUTPUT @ SIEMENS :-D (mirrored)

xrandr --output HDMI2 --mode 1600x1200; # it still works :-D

xrandr --output HDMI2 --mode 1600x1200 --right-of HDMI1; # EXCELLENT, now the second desktop is actually usable

xrandr --output HDMI1 --mode 1680x1050 --primary --left-of HDMI2; # to set the IIYAMA@HDMI1 as primary mon

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