Hello! I have seen this kind of problem for everyone out there who owns RX 480. When I am gaming or doing some graphics intensive works, after a few minutes, the whole PC gets weird Grey/Green/Black screens and gets hard freeze! I have to force reboot my PC. I'm a new consumer for this card, purchased an 'ASUS STRIX RX 480 8GB'. I have tried working with the very old Driver (16.20) which came along with the Graphics Card CD, and I found it's okay, not freezing like in the latest drivers (experienced both in 16.12.2 and 17.1.1). So, it is of course maybe the driver issue. I've also tried playing with the Driver's 'Global WattMan' settings a lot but, didn't help at all. I mostly observed this issue when playing on Ultra Settings and when temperatures are around 78-85 degrees Celsius. I'm kind of disappointed as this is my first ever Graphics Card. But, I know you can fix-off the issues anyway.
There are also some YouTube videos - MSI RX-480 Gaming X 8G Freezes on every game - YouTube; XFX RS RX480 Crash (Unigine Heaven 4.0 Benchmark) - YouTube
I really really request you to kindly fix this issue in the next Driver Update. Thank you!