I've spent a lot of time troubleshooting this problem and unfortunately have not solved it.
I'm basically trying to drive a seiki 3840x2160 screen at 30hz over hdmi on my samsung laptop which has an 8770m and an intel hd4000 video adaptor.
The only amd drivers i can get to even install is the beta 13.11 driver(which would not install with linux kernel 3.9, had to revert to 3.5 btw), but this causes all kinds of problems with the screen even before even trying to run at full resolution. It basically makes the computer unusable in mirror mode at 1080p. I currently have the best luck running the intel driver, so all amd drivers have been removed. But then i can only drive the screen at about 14hz.
I've come to a point where i can either try newer intel video drivers, which would require me to upgrade to at least ubuntu 13.04, and im pretty sure would make it impossible to install beta radeon drivers because of the newer kernel. i dont want to do this.
Is there a possibility i can get this to work properly with amd? Please advise...