I just built a computer, it has the new i5 and the r9 280x, when i installed on the os i was useing the gpu as viedo output with hdim, worked fine and everything then finished installing, and it rebooted and after reboot the asus motherboard splash screen appears then it goes black and nothing. So far i have checked that the on board works. and the pcie cable is fine.
You'll need to go into the bios and select the dedicated card as opposed to the on-board graphics.
I originally tried that, and I could only go to if it was set to the on board abd the gpu can't be plugged in to use that, I was using my tv with an hdmi cable, so I took it and plugged it into my monitors with dvi cable and it displays it just fine so then I went to bio and set pci e as the output and then shut down abd went to the tv and it worked