Hello, I've just bought a 12 Core 2012 cMP with an MSI Radeon R9 280X graphics card. I'm trying to get it to work with a 4K Dell P2715Q display, but having some issues. 1st I tried the supplied DP to mDP first and all I got was a black screen. 2nd I tried an old display and connected it to the DVI port with the Dell P2715Q disconnected and it worked fine. 3rd I tried a mDP to mDP cable and it worked fine. Then I rebooted to check it wasn't a one off and I got a white screen. So, I swapped the displays over again and the old display worked fine again. The I went back to the Dell P2715Q and it worked fine too. But again on a reboot I got the white screen. Seems somehow the old display is resetting the graphics card and lets the Dell P2715Q turn on once. I can't keep on swapping monitors everytime I want to use the Mac Pro. Does anybody have any idea how to resolve this? Thanks.