Ok so I looked everywhere and I'm still not been able to find a solution for my problem.
I'm running Ubuntu 11.10, with Unity 3D and ATI Catalyst 11.11, I have an ATI Radeon HD 6870 and I have a monitor with a resolution of 1600x900 connected by DVI and a TV with a resolution of 1920x1080 connected by HDMI.
So what I want to do is to set a dual monitor configuration I've tried in the Catalyst using my monitor as first monitor and the TV as second and choosing the "Single display desktop (Multi-desktop)" on the TV properties but I didn't get any result, then I tried from the "Displays" section on Ubuntu and I got this message:
"The selected configuration for displays could not be applied required virtual size does not fit available size: requested=(3520, 1080), minimum=(320, 200), maximum=(1920, 1920)"
The only way that the configuration could work was my monitor on the top of the TV instead being side to side "so they don't exceed the resolution" but that don't work for me
So later and after reading a lot of posts I realize that that Catalyst have a bug and if I execute the command
sudo amdcccle it starts the Catalyst and when I set up "Single display desktop (Multi-desktop)" on my second monitor (the TV) it ask me to restart so I can have that configuration (everything fine until here). But my problem is that when I restart my computer I got my first monitor fine but in my TV I got a blank screen and instead of the mouse I got an X, somebody know how to fix this??? and if that have something to do with the resolution?? because I'm planing to buy another 1600x900 monitor so I'll have a triple display configuration.