one advice for making 6+ gpu rigs: first of all make sure that one single cards shows picture on monitor stabbed in EVERY single PCIe and M.2 or PCIe splitter or whatever else you use, until than you have to play with those GEN1,2,3 settings. Mine board (h270 plus) is working with everything set to GEN2. Also not to mention that 4g decoding ON is must option. For 8+ GPU you have to use win10 (dont know about win 8.1), 7 gpu works fine on win7. Also have in mind that m.2 adapters are shitty quality and half of them doesnt work, so picture test is must option