% cvt 1920 1200 60
 # 1920x1200 59.88 Hz (CVT 2.30MA) hsync: 74.56 kHz; pclk: 193.25 MHz
 Modeline "1920x1200_60.00"  193.25  1920 2056 2256 2592  1200 1203
 1209 1245 -hsync +vsync

 % xrandr --newmode "1920x1200_60" 193.25  1920 2056 2256 2592  1200
 1203 1209 1245 -hsync +vsync
 xrandr: Failed to get size of gamma for output default

 % xrandr --addmode default 1920x1200_60
 xrandr: Failed to get size of gamma for output default

 % xrandr --output default --mode 1920x1200_60
 xrandr: Failed to get size of gamma for output default
 xrandr: Configure crtc 0 failed

 % xrandr -s 1920x1200
 Failed to change the screen configuration!

 % xrandr
 xrandr: Failed to get size of gamma for output default
 Screen 0: minimum 1600 x 1200, current 1600 x 1200, maximum 1920 x 1200
 default connected primary 1600x1200+0+0 0mm x 0mm
    1600x1200     77.00*
    1920x1200_60  59.88