10.10.3 breaks support for ATI video cards
The 10.10.3 update has broken support for a bunch of ATI video cards that worked just fine under 10.10.2. This is for my Mac Pro 5,1. Some folks also reported issues with breaking support for Nvidia cards, but have mentioned that the latest Nvidia beta drivers might work.
There is a thread that may be found here that has some details:
and here (reverting back to 10.10.2 fixes things):
http://forums.macrumors.com/showthread.php?t=1864352
Specifically, my Visiontek Eyefinity 6 7750 stopped working, and another users Radeon 7770 stopped working. Yet, the 7970 continues to work. Reverting to the old ATI 5770 that came with the machine renders it usable. This is a problem as the 7750 only took a single slot, and the two 5770s eat up 3 slots so I can't use my USB 3 card, etc.
I remember this once happened before. I think it was with the 10.9.2 update which borked a bunch of video cards that worked fine under 10.9.1, and then were again made to work just fine with the 10.9.3 update.
All the 'standard' fixes have been attempted. Clean installs. Fix permissions. Etc.
Not sure why apple would seemingly disable support for these cards, other than by accident, I assume, much like happened with the 10.9.2 update.
Also not sure if just copying the correct driver from 10.10.2 might solve the problem until Apple get's around to fixing the issue. Has anyone tried? Any suggestions would be appreciated. Thanks!