X99-A wont post after NVMe install - Q code 95

[AlexiTQ]

Earlier today I installed an NVMe drive in the M.2 slot. At first it seemed to work fine. The drive was found in both Windows and MacOS, I formatted it and installed MacOS High Sierra on it. Then, for no apparent reason, after a reboot I was greeted by a black screen. No display input and no peripherals working.

Tried disconnecting everything but the NVMe drive plus keyboard and mouse. I tried with only one SATA SSD. I reset CMOS and it posted once, but no keyboard working so I could not enter BIOS. After that it was dead again, even after a second CMOS reset. I guess I only managed to lose my saved BIOS settings?

It’s all the same no matter what. Q code 95 - PCI resource acquisition.

I have checked *the graphics card and tried different display port connectors. It’s seated properly and the power connectors won’t go anywhere.

So, well... what the heck? And, help please?

My setup:

X99-A motherboard
I7 5820K
16Gb Corsair Vengance
Samsung 850 EVO 250Gb
Samsung 850 EVO 500Gb
Samsung 970 EVO 500Gb
Asus STRIX 1080Ti*

[AlexiTQ]

Since posting I have tried removing the graphics card. That got it to recognize the keyboard and mouse. Once. After that it failed again. I’ve also tried different PCI-E slots.

Tried unplugging the water pump, remembering that I’ve had similar issues once with a broken pump. I guess a broken pump on a fan header can make the motherboard go nuts, but that wasn’t the case this time.*