I have install two amd HD 7470 adapter cards on my red hat 6.5 Linux PC.
I use the dvi port and the display port on the first display card to connect the first and second monitors.
Then I use the dvi port on the second display card to connect to the third monitor.
I have installed the amd-catalyst-13.12-linux-x86_x64 driver.
I run the command /usr/bin/aticonfig --adapter=all --initial
After reboot I found that I can configure the first and second monitor to be one desktop.
Screen object can move between these two monitors.
However, the third monitor was seperated as an individual desktop which means screen object cannot move to the third screen.
I tried other command like "aticonfig --dtop=horizontal --overlay-on=1" but didn't success.
What command should I use to extend the desktop to the third monitor?