Greetings, I have a Mac Pro (4,1) running Mavericks (10.9.5) with an AMD 7850 (non-EFI) and have been experiencing bizarre graphical artifacts as can be seen below. Dragging windows around is very stuttery and exhibits peculiar duplication artifacts. If I disable vsync (demonstrated in the video), the artifacts disappear and dragging windows becomes perfectly smooth at the cost of introducing tearing. These issues do not occur with this GPU under any version of OS X other than Mavericks. Stranger still, neither my 7750 (non-EFI) nor GTX 680 (EFI flashed) produce these issues under Mavericks. If anybody could shed some light on this bizarre situation, I would be very grateful. Thank you, Troy.