~$ cvt 1280 1024
# 1280x1024 59.89 Hz (CVT 1.31M4) hsync: 63.67 kHz; pclk: 109.00 MHz
Modeline "1280x1024_60.00"  109.00  1280 1368 1496 1712  1024 1027 1034 1063 -hsync +vsync

~$ xrandr --newmode "1280x1024-new"  109.00  1280 1368 1496 1712  1024 1027 1034 1063 -hsync +vsync

~$ xrandr --addmode LVDS1 1280x1024-new
X Error of failed request:  BadMatch (invalid parameter attributes)
  Major opcode of failed request:  150 (RANDR)
  Minor opcode of failed request:  18 (RRAddOutputMode)
  Serial number of failed request:  27
  Current serial number in output stream:  28