My system used to display the Full HD resolution - the native, very well on the Karmic.
I upgraded my system to Maverick and the maximum 16:9 resolution X server supports is 1280x720.
As far as I can remember, I didn't have to do any changes for the display back when I originally installed 10.04.
lspci, the graphics card I have is the one follows:
02:00.0 VGA compatible controller: ATI Technologies Inc Manhattan [Mobility Radeon HD 5000 Series]
How can I get back the high native resolution?