Gfilui

I have Ubuntu 16.04 on a Lenovo T420s. I'm trying to troubleshoot my screen resolution.

I believe my laptop has a 1600x900 resolution, but strangely the largest resolution option available is 1440x900.

Also, I'm confused why the "maximum" is 32767 x 32767

$ xrandr
Screen 0: minimum 8 x 8, current 1440 x 900, maximum 32767 x 32767
LVDS1 connected primary 1440x900+0+0 (normal left inverted right x axis y axis) 0mm x 0mm
 1440x900 60.15*+ 59.89 
 1360x768 59.80 59.96 
 1280x800 60.00 
 1152x864 60.00 
 1024x768 60.00 
 800x600 60.32 56.25 
 720x450 60.00 
 640x480 59.94 
DP1 disconnected (normal left inverted right x axis y axis)
DP2 disconnected (normal left inverted right x axis y axis)
DP3 disconnected (normal left inverted right x axis y axis)
HDMI1 disconnected (normal left inverted right x axis y axis)
HDMI2 disconnected (normal left inverted right x axis y axis)
HDMI3 disconnected (normal left inverted right x axis y axis)
VGA1 disconnected (normal left inverted right x axis y axis)
VIRTUAL1 disconnected (normal left inverted right x axis y axis)
 1600x900_60.00 (0x14f) 118.250MHz -HSync +VSync
 h: width 1600 start 1696 end 1856 total 2112 skew 0 clock 55.99KHz
 v: height 900 start 903 end 908 total 934 clock 59.95Hz
 32768x900_60.00 (0x150) 2435.500MHz -HSync +VSync
 h: width 32768 start 34648 end 38120 total 43472 skew 0 clock 56.02KHz
 v: height 900 start 903 end 913 total 934 clock 59.98Hz
 32768x900_59.80 (0x163) 2427.250MHz -HSync +VSync
 h: width 32768 start 34648 end 38120 total 43472 skew 0 clock 55.83KHz
 v: height 900 start 903 end 913 total 934 clock 59.78Hz

You can see in the last three lines that I've been trying to add a new mode to LVDS1 by following these steps:

$ cvt 1600 900 60

Output

# 1600x900 59.95 Hz (CVT 1.44M9) hsync: 55.99 kHz; pclk: 118.25 MHz
Modeline "1600x900_60.00" 118.25 1600 1696 1856 2112 900 903 908 934 -hsync +vsync

Copy/paste the modeline into a newmode...

xrandr --newmode "1600x900_60.00" 118.25 1600 1696 1856 2112 900 903 908 934 -hsync +vsync

And then, add the mode to LVDS1...

xrandr --addmode LVDS1 1600x900_60.00

Which returns the error

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: 42
 Current serial number in output stream: 43

How do I troubleshoot this error and add a custom resolution?