I just got an asrock H110 btc pro mainboard and boy is it particular about the card order with RX480s, took me hours to get all the cards online. I also got some powercolor RX460 mining OEM cards with the board, they won't even work on the H110 and I can only get a max of 4 cards to work together on an old gigabyte 990 ud3. This is all under Ubuntu 16.04 and windows has a gpu limit so that won't work. I think I'm SOL on these 460s until I get a new mainboard.

Getting all the GPUs in a multi-GPU system to play together can definaty be a challenge.