I have used these mobos with rxOC; when using more than 6x GPUs the driver and x stop working together and you will need to follow the process in this post for now:

https://bitcointalk.org/index.php?topic=1984302.msg21875302#msg21875302 (https://bitcointalk.org/index.php?topic=1984302.msg21875302#msg21875302)