Fudzilla posted AMD RX 480 successfully flashed to RX 580
A quote from the article:
Several AMD Radeon RX 480 graphics cards have been successfully BIOS flashed to Radeon RX 580, allowing them to run at higher GPU clock speeds.AMD RX 480 successfully flashed to RX 580 @ Fudzilla
Originally published by Techpowerup.com, one of the users at its forums has managed to flash its XFX RX 480 8GB graphics card to RX 580 by using the Sapphire RX 580 BIOS. This allowed the card to hit 1411MHz clock without any problems and the card appears to be stable in both The Witcher 3 and Furmark.