andrea@centurion:~$ xrandr --newmode "1680x1050_60.00"  147.14  1680 1784 1968 2256  1050 1051 1054 1087  -HSync +Vsync
xrandr: Failed to get size of gamma for output default
X Error of failed request:  BadName (named color or font does not exist)
  Major opcode of failed request:  153 (RANDR)
  Minor opcode of failed request:  16 (RRCreateMode)
  Serial number of failed request:  19
  Current serial number in output stream:  19