AMD R9 390 - Gray screen of death or?

[Temuka]

I've been refraining from giving a technical opinion since most of my experience with graphics cards is with regard to low/medium range cards (the r9 380x is the highest end card I've owned relative to its time, which is what I have now). Admittedly it sounds to me like the card is at fault and you've tried everything I can think of.

Contacting the manufacturer even if it's not in warranty may result in more useful suggestions as well.

Running at stock - if you run it for a few minutes with heavy load, what temps do you get?

I ran furmark for 10 minutes,max was 74c

 

[LTC8K6]

I haven't changed thermal paste on gpu for 2,5 years if you mean that,but what about RAM ?

Didn't know whether the ram also had heatsinks with TIM.

 

[Shmee]

Sounds like the hardware is unstable at the stock clocks, as it is fine when underclocking. You can try the following: if you can get it repaired under warranty from sapphire, or as a cheap enough out of warranty repair, do that.

If unable to repair or replace from sapphire, you could underclock, as already tried, or try a different VDDC or memory voltage to try to stabilize stock clocks.

If none of these suit you, it is not a bad time to get a new card. Both AMD and Nvidia offerings are dropping in price outside of the new released RTX 2k series.