Quote from: sang on June 21, 2017, 07:34:12 PM

Update:

Switching to Windows 10 Pro from the previous Server 2012R2 has mostly fixed this. 8 gpus work no problem now on both my Asus Z270-A and Asus Z-270-P boards. 9 GPUs on the Z270-A (using two M.2 adapters) still refuses to work though, it will boot into windows and then instantly lock up completely (cant move mouse or interact).

That's a limitation of Windows. In Windows 10 you can run up to eight cards using the same drivers, so you can eight AMD cards + eight Nvidia cards. Either add a different card for the 9th GPU or switch to ethOS, smOS which are based on Linux.