This post help me a lot.
I was trying bring up my four MSI GTX 1080 TI Gaming X Trio (connect with riser), but it was a impossible mission, until now... I found this video
https://www.youtube.com/watch?v=4cd1qoTAHmA and this post, but the cards was not recognized. Then I restart my Windows Server 2012 about five times and, wait, WTF, the GPUs were recognized in device manager... 205 MH/s minig Ethereum ...
Sometimes, randomly, one card turn down, and I am forcing reboot the system. Anyone with this problem? o/