So I have a UEFI install of Windows and I'm having display booting issues when disabling CSM.

I have 3x AOC G2460PQU displays connected to my PALIT GTX 980 via Mini DisplayPort.

Everything works fine, but if I disable CSM in BIOS, I sometimes get a few strange issues when booting.

Firstly, sometimes when booting one or two of the monitors don't get detected by Windows, it can sometimes take 10 - 15 seconds for Windows to detect one of the monitors on boot. Also, sometimes the monitor doesn't get detected at all by Windows and in "Display settings" the monitor shows as "disconnected" and cannot be re - enabled unless I reboot or turn the monitor on and off. This doesn't just happen with one specific monitor, it can happen with any 3 of them.

Another problem that happened to me was when I had to restart my PC yesterday to update AVG, the Windows login screen changed from the right monitor (the monitor set to main) to the middle monitor and just got stuck. The login screen would just keep flashing on and off, over and over again. I had to do a hard reset (press power button) to get out of this cycle.

Finally, when in BIOS (the BIOS appears on the LEFT screen) the middle and right monitors try and turn on by themselves (power light goes from orange to green) and then say "no signal" and turn off again, this happened every few minutes. It is like they are trying to be detected by something.

So what is causing this? Is it the monitors? The OS? The GPU?

Many thanks