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I have two X200 Thinkpads. They both have the rather annoying problem that, unless the display backlight is set to its maximal value, it emits an unbearable noise. The odd thing is that one of them boots with the max. value and the other does not. It is also impossible to set the second computer's display to the max. brightness value by using the brightness-up button (it will only reach 779942 of 846600). I have to
cat /sys/class/backlight/intel_backlight/max_brightness >/sys/class/backlight/intel_backlight/brightness
Now the sound goes away but only until the next reboot. Is there anything I can do to make the brightness value persistent across reboots?
PS. I understand that I can run a script on startup, but something is making my first comptuer different and I would like to know what. I have tried this using the exact same OS (the same live USB), and both computers have the same BIOS version (from 2012; 7.22?) and settings. The difference is also there in the BIOS setup, before loading any OS.
(PS II. I might add that the problem does not exist in Windows, even with the screen dimmed.)