https://www.youtube.com/watch?v=VAuAtJxe3BM Yosemite has FPS problems compared to Mavericks. At least on my 15" retina MBP 2013 (16gbram + i7 + dedicated graphics) Beam Sync seems to be the problem when connected to a Cinema Display. Best seen with screen magnifying. PS: The FPS tool you see is Quartz Debug by Apple itself. ========================== 1. Beam Sync Automatic (OSX Default) Result: Stuttering here and there on the UI. 2. Beam Sync OFF Result: Smooth user experience. ========================== Some people might say: Hey Beam Sync is for keeping everything at 60FPS to prevent tearing effects (when the display gets more FPS than it can handle) BUT When Beam Sync is on yosemite drops way below 60fps most of the time (in my case I usually get 40-50 fps). When I disable it, it stays way above 60fps so my display get's at least a fps for every refresh. What do you guys think? To me it seams that Beam Sync in Yosemite is differently implemented than in Mavericks (in Mavericks it stays on 60FPS without high variance).