I have the proprietary AMD Catalyst drivers installed in Linux Mint 15, (analogous to Ubuntu 13.04 Raring), and I'm having a very weird issue.
I have both an HD 7850, and an R9-290, running on an A8-6600K APU. I've tested with both cards in, just the 7850, and just the 290, and even with just the APU, but I consistently get the same issues.
A Source-engine game gives me quantifiable results, as it has a frame counter I can enable. With Tear-free DISABLED in the CCC, and with vsync either enabled or disabled in game (it has no effect either way), my frame rates go from 60, down to the teens, and up into the 180's, VERY rapidfire. Naturally, I'm getting screen tearing AND more input lag than I would expect from the framerates being in the teens. I've removed the proprietary drivers and reinstalled, tried the Beta drivers, stable drivers, everything, and they all do the same thing. This happens on ALL games.
Google doesn't seem to want to assist me with this specific issue, so perhaps someone here has a clue as to what is going on?