How to run 4 GPU cards when the MSI Z270 SLI Plus only has 3 slots? 
Hi,
You have to use risers: http://mylifegadgets.com/USB30RISERS for the small slots.
Ok thanks for explaining. My mobo has:
-2x PCI-e 3.0 x1
-PCI-e 3.0 x4
-PCI-e 3.0 x16
How many 1080Ti can I connect?