https://bugs.freedesktop.org/show_bug.cgi?id=73911
--- Comment #16 from scix55@gmail.com --- I'm experiencing the same problem with an AMD A10-4600M in an Asus N56DP laptop. I don't have an external screen to test at the moment, so can't be sure if it's evident there as well.
I tried the patch with both 3.13 and 3.14-rc4 (with some edits due to it not applying cleanly for the latter) and the patch actually causes a flickering black screen on boot, with some faint green line popping up periodically. Perhaps I applied the patch inproperly, though.
As far as the banding goes, the problem is particularly evident when running Steam and looking at the grey background, which is filled with multi-coloured banding.