My friend is running a rig with 4 RX 480 8GB Devil after market cards with the USB 3.0 and he has no issues. This tells me it's the quality of the risers you purchased are junk!
I have over 250 GPU's running and have been mining a long time. I will be happy to show you a BIG BOX of worthless USB risers. Every brand, color, manufacturer. Secondly, If your friend is running some 480's it is probably a new build - give it some time.

Kilo17 can you please provide a link to Amazon/Newegg/Ebay for the powered risers that you use and stand behind? I have done alot of research and have found quite a few that seems to work, but my mining farm is virtual... Ie it just exsists in my head since my wife thinks "Saving for vacation next summer is more important than your stupid mining hobby"...
