Hi all! I just bought a used RX 480 4GB (Sapphire Nitro, not Nitro+).
I installed it last Sunday by doing this: I downloaded the latest RX 480 drivers from AMD's site, rebooted into safe mode, used DDU to uninstall all graphics drivers, shut down PC, replaced my GTX 750 TI with the RX 480 and connected my PSU's 6+2 pin PCIE connector.
So I booted up my PC, everything was working great with no problems, I did some web browsing and a couple of Dota 2 games. I don't have direct access on my PC right now since I'm only home on weekends. My brother uses it on weekdays though, mostly just browsing, web development and Dota 2. So my brother told me that this Monday and Tuesday, the PC had no issues, but just this Wednesday, it had random black screens (literally, NOT "No Signal" black screens) that lasts for a second. It occurred about 5 times while playing Dota 2, and a few more afterwards while doing web development. He shut the PC down but later that night, when he played Dota 2 again, black screens occurred again about 5 times.
System Configuration:
Motherboard: Asrock H61M-DGS rev 2.0
CPU: Intel i5 3470
Memory: 8GB DDR3
PSU: Thermaltake Smart SE 530W
GPU: Sapphire Nitro RX 480 4GB (was Palit GTX 750 TI)
OS: Windows 10 x64
Some background on where I got the gpu from: A shop that sells used parts from Korea. I had the gpu shipped to me, they gave a 1 month warranty, so it can be replaced if proven faulty. It makes me wonder though why they were selling Sapphire Nitro for RX 480, and not Nitro+. I searched the net for Sapphire RX 480, and very rarely does Nitro (non plus) come up, at this point I'm starting to suspect that the gpus they are selling have been used in mining. I found out though, that the random black screens have been an issue with AMD gpus these past few years, so maybe the gpu I got isn't faulty after all and that my issue is maybe just the same as everyone else's.
Still, I'm not really sure how to diagnose the real problem, I mean how do I tell if it's because of the gpu being faulty, something software related (drivers, win10), or something else entirely. Would a stress test like Furmark help determine if its a hardware issue? I can only list down things to do before I get home on Sunday. Any help would be greatly appreciated. Thanks! 
