HI: I have a HD7970 flashed the efi rom .But I have some problem . If I connect a 4K monitor to the MINI DP interface alone, the machine will not start. If I have another DVI 1080 monitor, no boot screen, but wait a minute, the machine will have login OS interface. If I drop the 4K monitor, and then connect a 1080 of the display to the graphics card of any interface, you can have a normal boot screen, How do I do? There is no perfect support for 4K graphics card. Thank you!