I am running a XFX Radeon R9 280X with a Samsung U28D590D monitor. Using HDMI for 4K @ 30Hz works well, but when I switch to using the mini-dp port to get 4K @ 60Hz I get ridiculous flickering! It starts with the splash screen and continues. If you drop the resolution the flickering goes away. Booting the same rig into windows displays 4k @ 60Hz without any issues. I have tried the open source drivers, the 14.6 beta drivers and the latest omega drivers without any luck. I have reached out to AMD Tech Support but no response as yet. Can anybody suggest anything else to try?