What's the 1+8 trick?. It also seems like you won't be able to claim the warranty because of the bios (you should try contacting Sapphire anyway), also probably why the previous owner sold it, the card was showing signs of a failing.

Btw, I'm running 7x RX 470 and 480 cards, and they've been awesome and stable. Just a little underclock and now all run below 68ºC.