Sigh, tried a backup PCI 6+2, even disconnected the breakout for an extra fan that's in the other PCI slot on the PSU, so only the 1080 was drawing power, other than my HDD and SSD, same problem, black screen on boot.
Gonna do a quick test, something I hasn't thought of before...
Oh my god it IS booting successfully, and I can login to Windows but the 1080 won't display ANYTHING On the screen! That means the 1080 is receiving power (I think), or it wouldn't boot at all? I'd try every other video output but I'm pretty sure already the same thing was happening on DVI, HDMI, and DP, I just never tried logging into windows...
Whats odd is when I booted the first time to install the drivers when the card arrived earlier this week, it was outputting to the monitors, only it was displaying horizontal green/blue lines like
this
Swapped the HDMI cable onto my other monitor, currently have the same problem, no video output, but I can boot into Windows just fine. The monitors not going to sleep either...
Did gigabyte actually have the gall to send me back a broken 1080 TWICE, even claiming to have swapped it for a new one the 2nd time?
R9 390 back in the case, fan. Breakout cable plugged into the PSU, boots up fine. Time to reinstall my driver's for the 5th time this week lol. Hopefully the CS rep actually makes sure they honor the gpu swap he promised last time, really don't wanna have to do all this again