NOTE: See the last two pages for a solution that worked for me... all the other pages for ways that didn't work for me but may still be a solution to you
I am currently running 12.04
(but my question will pertain to any of the releases of Ubuntu so I don't think posting in +1 is needed).
I have a Radeon HD 6850 and the drivers coming with Ubuntu where not working properly so I downloaded and installed the drivers from the AMD/ATI site. Installed and working at the moment I am glad to say.
My issue is that I am getting a maximum resolution (I can use) of 1600x900 and my screen (LG Flatron E2251) has a naitive resolution of 1920x1080. I was finally able to achieve this in Windows by using a setting in the Catalyst Control Center (which was set to limit the maximum resolution in Windows). There is no such option in the Catalyst Control Center for Ubuntu.
So I started looking around and found this site - and I tried to add the resolution of 1920x1080 at a refresh rate of 60hz.
nlsthzn@circle:~$ cvt 1920 1080 60
# 1920x1080 59.96 Hz (CVT 2.07M9) hsync: 67.16 kHz; pclk: 173.00 MHz
Modeline "1920x1080_60.00" 173.00 1920 2048 2248 2576 1080 1083 1088 1120 -hsync +vsync
Problem is on the next step:
xrandr --newmode "1920x1080_60.00" 173.00 1920 2048 2248 2576 1080 1083 1088 1120 -hsync +vsync
Any assistance would be appreciated!
nlsthzn@circle:~$ xrandr --addmode CRT1 1920x1080_60.00
X Error of failed request: BadMatch (invalid parameter attributes)
Major opcode of failed request: 156 (RANDR)
Minor opcode of failed request: 18 (RRAddOutputMode)
Serial number of failed request: 49
Current serial number in output stream: 50