SHLEEM

Ok, so I'm starting to lean towards a PSU problem. Tried to do a ram test with the HD 6850 inside and the system like the fellas above suggested and it just wouldn't boot (everything runs fine without a gpu). My first thought was that PCIE slot was screwed, even tho the pins don't look damaged at all. So I threw together a reallly old system from spare parts I have laying around and tried the HD 6850 there and ,so far , it's working great. I also tried running my current computer with an ancient Radeon X1800 gto in it and after clearing CMOS it booted and is running fine. So, considering that the only GPU that appears to run stable on my system is the Radeon X1800 GTO, which besides being ancient also happens to have a much lower power consumption compare to RX480 and HD6850, can I conclude that the fault is with the PSU and not the PCIE slot/Motherboard or the GPU?

Ok, running memtest right now. BTW, if I check the PSU with a Multimeter, will it be enough to determine if it's faulty or could it be something that only occurs at random intervals?

Yeah, sorry, just edited in the system specs. And no, since the system is completely stable without a GPU I assumed that the ram could be ruled out.

Here hoping for some help from the great and faceless internet crowd, so here's my problem: Two days ago my year old build froze during basic web surfing. After a few restart attempts with no video signal I tried switch to the integrated GPU and found out that the computer was actually booting just fine but not detecting the RX 480 (neither in bois nor in windows). So I tried clearing cmos, reflashing MB's bios, reinstalling the RX 480 into the second PCIE, and using other power connectors on it to no avail (the led lights always lighted up but not much else). Finally, I tried replacing the RX with my old Asus Radeon HD6850 and it worked fine, i even did a few stress test and everything went well. So I RMA'd the RX 480 today and was ready to wait for the retailer to get back to me. Buuut then I come back from work today only to find my PC (currently with the HD6850 in it) frozen. After a few restarts I found out that the computer would freeze (with sound continuing working fine but a frozen screen and no input reaction) after a short and random period of time, like 1-5 min, even in bios which I reset to default settings just in case. Those freezes persisted until I removed the HD 6850 and switched back to the internal GPU, then it became completely stable again. So, my question is, do you think that my original assessment that the RX 480 was faulty is wrong and maybe the problems originated from a faulty PSU or motherboard/PCIE slot, rather than the GPU? PC specs: Motherboard: Asus H170 PRO GAMING GPU: SAPPHIRE NITRO+ Radeon™ RX 480 8G D5 OC CPU: Intel I7 6700 3.4ghz RAM: Corsair Vengeance LPX 2x8GB DDR4 2400MHz SSD: Sandisk Plus 2.5 240GB PSU: Antec Basiq 700w VP700p