I have an issue. My monitor is plugged into the 1 hdmi slot on my desktop GTX 1080 graphics card but OR needs to be plugged into that slot. So my monitor needs to be unplugged for OR btw it is an ASUS 4K PC Monitor with 4 hdmi slots only. So when I unplug the monitor hdmi cable from the graphics card on my pc where do you I plug the monitor in for this to work. I have on the motherboard a DVI connection so I have tried an hdmi/dvi adapter but that does not work. I also have an hdmi slot on the m/board If I plug the hdmi cable from the monitor into the m/board hdmi directly it does not work with either a standard hdmi cable or 2.0 hdmi cable. If I obtained a displayport to hdmi adapter would I then be able to connect the monitor via the hdmi on the motherboard? Am i right that the displayport to hdmi adapter will convert the monitor to work off the motherboard hdmi. If I am wrong then can someone offer another solution.
Only 1 HDMI slot on your GPU? Nothing else? You can't use ports on the motherboard, it would not use your GPU then, only the integrated motherboard GPU would be used. You need DVI or Display/Mini-Display port on your GPU for the monitor.
You can use your integrated graphics on your mobo to run Windows if you want. I have my 3rd monitor run by my Mobo and my other 2 and my rift run from my GPU. I'm confused why your GPU doesn't have more connections though? I have an HDMI, 2 x DVI and a DP and I only have a 780ti. Don't you have a DP on your 1080?
If you want to use your mobo graphics for Windows then go into display settings then make sure your integrated graphics are enabled in device manager in Windows and plug in the monitor.