How to increase resolution in Ubuntu 12.04 LTS to 1280x800 if it is not found in available modes?

Question

I have a problem with my screen resolution - it's native is 1280x800 but I can get only two resolutions (from xrandr commend):

joanna@joanna-M51SE:~$ xrandr
 xrandr: Failed to get size of gamma for output default
Screen 0:minimum 800 x 600, current 1024 x 768, maximum 1024 x 768 default
   connected 1024x768+0+0 0mm x 0mm    1024x768       61.0*     800x600 
   61.0

I've tried to add this resolution using cvt commend (this is what I get):

joanna@joanna-M51SE:~$ cvt 1280 800
1280x800 59.81 Hz (CVT 1.02MA) hsync: 49.70 kHz; pclk: 83.50 MHz
Modeline "1280x800_60.00"   83.50  1280 1352 1480 1680  800 803 809 831 -hsync +vsync 

I've tried each advise I found on the web but nothing solves the problem.

I am using a laptop:

Video card: ATI Mobility Radeon HD 3470

Screen (matrix?): Samsung LTN154X3-L03

Can anybody help me?

Answer 1

You could add monitor mode with xrandr

xrandr --newmode "1280x800_60.00"   83.50  1280 1352 1480 1680  800 803 809 831 -hsync +vsync

Then, you could add mode to the xrandr with output (my example VGA1, if you are using different, you should write whics name),

xrandr --addmode VGA1 "1280x800_60.00"

Then, select new resolution from the Display window, or use xrandr,

xrandr --output VGA1 "1280x800_60.00"