Hey guys, I have been fighting this for the last 5 hours and I finally had to throw in the towel and post here hoping for some suggestions. Here's the hardware: MSI X99S GAMING 9 ACK (latest BIOS installed) 6850K CPU 2 x G.SKILL Trident Z 3200-14-14-14 4 x MSI 1080Ti Sea Hawk EK X 1 x Samsung 950 PRO M.2 512GB Here's a pic of the rig: As you can see, there are only 4 cards installed in slots E1, E2, E4 and E5. However, a run down of what BIOS believes is installed in the slots shows the following: PCI_E1 running at x8: PCI_E2 running at x8: PCI_E3 running at x8: WFT, there is nothing in this slot! PCI_E4 running at x16: Why? This should be running at x8 PCI_E5 running at x8: PCI settings as follows (believe, my have tried everything under the sun here, but nothing changes the above readings): Oh yeah, and the 950 PRO does not show up here: (nor did it show up in the board explorer pics above) But it does show up here: Integrated Peripherals settings are all left at default: Setting this made booting into the Win10 install already on the 950 not work: So, with WHQL support disabled, I'm able to boot into Windows, but within a few minutes, things get unstable and I'm not able to save anything to the 950 in the M.2 slot. Also, I'm completely unable to boot into Ubuntu from a USB stick. Stick works just fine in just about every other rig I have. So wtf is going on? Defective X99 mobo? Should I rip out 3 of the 1080Ti's? Really don't want to as everything has been leak tested at this point.