title: setting 4k resolution with xrandr fails with badmatch error
body: <p>I have a 4k monitor and try to set my Ubuntu 14.04 LTS to use it. Since there is no 3840x2160 option available in system settings and NVIDIA X Server Settings - the only way to do that is using xrandr tool.
  So I type: </p>
  
  <pre><code>gtf 3840 2160 60
  
  # 3840x2160 @ 60.00 Hz (GTF) hsync: 134.10 kHz; pclk: 712.34 MHz
    Modeline "3840x2160_60.00"  712.34  3840 4152 4576 5312  2160 2161 2164 2235  -HSync +Vsync
  
  xrandr --newmode test87 712.34  3840 4152 4576 5312  2160 2161 2164 2235  -HSync +Vsync
  
  xrandr --addmode HDMI-0 test87
  
  X Error of failed request:  BadMatch (invalid parameter attributes)
    Major opcode of failed request:  140 (RANDR)
    Minor opcode of failed request:  18 (RRAddOutputMode)
    Serial number of failed request:  35
    Current serial number in output stream:  36
  </code></pre>
  
  <p>It seems like a common error, but other solution suggest modifying the /etc/X11/xorg.conf (that I don't have, I tried to create one and reboot but it does not help). Some others solutiond suggest using brackets around mode names - it does not help as well. </p>