TLDR: XFX Rx 480, 17.8.1 driver: Had 4 displays working: 21" TV, 24" Monitor, 21" Monitor, 4K TV. Tried to make the TV the primary/only active display and now if I have all 4 even plugged in the machine boots to black login and will go to a boot cycle.
So I have the setup mentioned above, the small (#1)TV and (#2, #3)2 monitors are on my desk, and the (#4)4K is next to it. My card has 3 DisplayPorts and 1 HDMI Port (small TV plugged into HDMI.) I've been using this setup since March. Yesterday I decided to do some gaming on the big TV, done this plenty of times before but this time I decided to make the (#4)TV the only display (so I wouldn't have the others glowing off to the side). In windows display manager, I disabled #1, then #3, no ill effects, I changed #4 to be the primary display, then I went to #2 and said "Disable this display" at that point #2 and #4 went dark for a few seconds (I think the Windows 'Confirm you want to keep these setting' might have been on the screen, then the back light on #2 came on but no image... Then Windows rebooted. After that the Windows boot up screen would show on #2 and #3 (this is normal, the #1 doesn't show anything until Windows logs in) but once the login screen was supposed to show it would go to black (the back lighting on #2 would cycle on a couple of times and then, the boot cycle would start.
I think I've narrowed it down to:
1) I can have #1, #2 and #4 plugged in and things work
2) I can have #1, #3 and #4 plugged in and things work
3) I can uninstall Radeon and all 4 work.
If I start with option 1 or 2, and try to add the fourth, all screens go black (with back lighting on #2) then will crash into a boot cycle.
I've tried clean uninstalling the drivers, (even tried the amdcleanup utility, though I assume it's outdated and just used to handle what the clean driver uninstall does)
I tried uninstalling the drivers, then starting with only one display plugged in, adding the others one at a time, and noticed that something (Windows or Radeon) is remembering past configurations (when I have #1 and #2 plugged init places #1 to the left of #2 and slightly lower, since I set it up this way a while back, then when I add #4 it remembers I prefer it to be to the far left, so in display settings it goes #4,#1,#2)
So what I'm assuming is happening is somewhere it's stored that when #2 and #3 are plugged in to switch to some invalid resolution/refresh or something and crashing out.
Does anyone have any idea of anything else I can try? #2 and #3 are what I use most for work and they seem to be the only ones I can't use together. I'm hoping I don't have to go to a backup image (for just trying to disable a display... urgh) and if that doesn't fix it, I may be spending a weekend reinstalling from scratch... Please save me from that...