Попробуйте прямо прописать монитор, вот мои файлы:
Modeline для своего разрешения можно сгенерировать с помощью команды gtf
/etc/X11/xorg.conf.d/50-monitor.conf
Code:
# Having multiple "Monitor" sections is known to be problematic. Make
# sure you don't have in use another one laying around e.g. in another
# xorg.conf.d file or even a generic xorg.conf file. More details can
# be found in https://bugs.freedesktop.org/show_bug.cgi?id=32430.
#
Section "Monitor"
Identifier "Default Monitor"
#
# ## If your monitor doesn't support DDC you may override the
# ## defaults here
HorizSync 55.93
VertRefresh 60
#DisplaySize 490 250
#
# ## Add your mode lines here, use e.g the cvt tool
#
# 1440x900 59.89 Hz (CVT 1.30MA) hsync: 55.93 kHz; pclk: 106.50 MHz
Modeline "1440x900_60.00" 106.50 1440 1528 1672 1904 900 903 909 934 -hsync +vsync
Option "PreferredMode" "1440x900_60.00"
EndSection
/etc/X11/xorg.conf.d/50-screen.conf
Code:
# Having multiple "Screen" sections is known to be problematic. Make
# sure you don't have in use another one laying around e.g. in another
# xorg.conf.d file or even a generic xorg.conf file. More details can
# be found in https://bugs.freedesktop.org/show_bug.cgi?id=32430.
#
Section "Screen"
Identifier "Default Screen"
#
Device "Default Device"
#
# ## Doesn't help for radeon/radeonhd drivers; use magic in
# ## 50-device.conf instead
Monitor "Default Monitor"
Subsection "Display"
Modes "1440x900_60.00"
EndSubSection
#
EndSection
