Is the game resolution that you select limited by your monitor resolution ? For example, if my monitor is 1400 X 900 and I select a gaming resolution of 1920 X 1200 (with an ATI 4870, will it be useless ?
no,why would you override the native resolution of your monitor
for example,you would in lets crysis 1440x900 get 40fps,but in other hand in 1920x1080 you would 15fps
if you interested,i think you should in catalyst control center see option force resolution and there you would be able to force full hd resolution