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https://askubuntu.com/q/1269346
Title:
Cannot use full resolution of external display
ID:
/2020/08/23/Cannot-use-full-resolution-of-external-display
Created:
August 23, 2020
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September 15, 2024
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First you don’t need to use sudo with xrandr.
Second you need to run cvt to get the settings to pass to xrandr --newmode. For example (on my 4K TV):
cvt -v 3840 2160 56
Warning: Refresh Rate is not CVT standard (50, 60, 75 or 85Hz).
# 3840x2160 55.98 Hz (CVT) hsync: 124.95 kHz; pclk: 661.75 MHz
Modeline "3840x2160_56.00" 661.75 3840 4152 4568 5296 2160 2163 2168 2232 -hsync +vsync
Then copy the Modeline output as input for xrandr --newmode:
$ xrandr --newmode "3840x2160_56.00" 661.75 3840 4152 4568 5296 2160 2163 2168 2232 -hsync +vsync
X Error of failed request: BadName (named color or font does not exist)
Major opcode of failed request: 140 (RANDR)
Minor opcode of failed request: 16 (RRCreateMode)
Serial number of failed request: 52
Current serial number in output stream: 52
The refresh rate is too high in this case so I reduced it to 54 Hz and repeated the process.