Hey. At First my English isn't so Perfect, but i will try explain. I have a Mac Pro 5.1 ,2x 6Core 3,46Ghz, 32GB Ram, 2SSD's with Apricorn Velocity Solo on PCI 2 and 3 Slot and GTX680 Mac Edition and 4K UHD ASUS PB287Q plugged on DP1.2 I'm using It for Music Production ,Graphics Design, and for Video Editing too. I have problems on HiDPI Resolutions, in Logic Pro X, Ableton Live 9 and another Apps . UI lag , freezes is very slow on scrolling, zooming etc. On 1080P is acceptable but on higher resolutions is very Bad.. I'm tried a non-Efi GTX980 but no difference.. I Have Yosemite 10.10.2 and all Nvidia Drivers like Web and Cuda are up to date.