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I edited /boot/config.txt to use hdmi_group=2 and hdmi_mode=4; one HDMI monitor is connected to the first connector. It starts at 1024x768 instead. Only when I explicitly run xrandr --output HDMI-1 --mode 640x480, the system actually switches to the desired resolution. Why are the settings in config.txt ignored (they work in general, e.g. I can select a higher resolution like 1280x960 and it works). OS is Raspbian Buster.

Edit: Here are some outputs:

$ tvservice -l
1 attached device(s), display ID's are : 
Display Number 2, type HDMI 0
$ tvservice -v 2 -m DMT
Group DMT has 14 modes:
  (prefer) mode 4: 640x480 @ 60Hz 4:3, clock:25MHz progressive 
           mode 5: 640x480 @ 72Hz 4:3, clock:31MHz progressive 
           mode 6: 640x480 @ 75Hz 4:3, clock:31MHz progressive 
           mode 8: 800x600 @ 56Hz 4:3, clock:36MHz progressive 
           mode 9: 800x600 @ 60Hz 4:3, clock:40MHz progressive 
           mode 10: 800x600 @ 72Hz 4:3, clock:50MHz progressive 
           mode 11: 800x600 @ 75Hz 4:3, clock:49MHz progressive 
           mode 16: 1024x768 @ 60Hz 4:3, clock:65MHz progressive 
           mode 17: 1024x768 @ 70Hz 4:3, clock:75MHz progressive 
           mode 18: 1024x768 @ 75Hz 4:3, clock:78MHz progressive 
           mode 21: 1152x864 @ 75Hz 4:3, clock:108MHz progressive 
           mode 32: 1280x960 @ 60Hz 4:3, clock:108MHz progressive 
           mode 35: 1280x1024 @ 60Hz 5:4, clock:108MHz progressive 
           mode 36: 1280x1024 @ 75Hz 5:4, clock:135MHz progressive 
$ xrandr
Screen 0: minimum 320 x 200, current 1280 x 1024, maximum 7680 x 7680
HDMI-1 connected primary 1280x1024+0+0 (normal left inverted right x axis y axis) 376mm x 301mm
   1280x1024     60.02*+  75.02  
   1280x960      60.00  
   1152x864      75.00  
   1024x768      75.03    70.07    60.00  
   832x624       74.55  
   800x600       72.19    75.00    60.32    56.25  
   640x480       75.00    72.81    66.67    59.94  
   720x400       70.08 
$ cat /boot/config.txt | grep hdmi_
hdmi_force_hotplug=1
hdmi_group=2
hdmi_mode=4

Edit 2: Seems to be a 'Pixel' specific problem, because I can see the Pixel splash screen at 640x480, but when the desktop has boot, it has reverted to a higher resolution. I'm using a subsequent xrandr now to force the resolution back to 640x480, but still wonder if this behaviour can be turned off in Pixel.

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  • what's the output of tvservice -m DMT ( you may need to add -v x where x is the device returned by tvservice -l) ... i.e. something like tvservice -v 1 -m DMT
    – Bravo
    Commented Jul 10, 2021 at 2:51
  • @Bravo I added the information in an edit
    – 0__
    Commented Jul 10, 2021 at 10:47
  • Pixel is DEAD, Long Live RPD
    – Milliways
    Commented Jul 10, 2021 at 12:31
  • ? I am using Raspbian Buster, and no intent to upgrade that ATM
    – 0__
    Commented Jul 10, 2021 at 12:33
  • what upgrade is there to Buster?
    – Bravo
    Commented Jul 10, 2021 at 12:44

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