Question HUGE problem with RX Vega 64

[Niels_7]

Hey guys,
alright so I'm super frustrated. I just bought a used Rx Vega 64, guy said it was working fine, and indeed it seemed to be okay when I first used it. However, I had to reset my PC entirely, and after reinstalling everything, including the latest drivers and whatnot,
I attempted to play Apex legends. Even before the reset, when I would play apex, I'd get only 130 fps while uncapped, and this confused me, cuz it should be as good as a 1080, and here I am with worse performance than my old 1060 gave me.
But wait, it gets better.
I tried launching fortnite today, and the GPU goes straight to 100% and sticks there, overheats and crashes. Even before playing the game, just on the loading screen. All the 8 led's go on, and the gpu makes a weird rasping noise, and overheats super fast. EVEN BEFORE BEING IN THE GAME!
After this I launched apex, where the same thing happened. I then capped my FPS, and sure enough this stopped the instant max punch out of the performance, but when in game, the GOU was at 70% usage and I was still getting only 90 fps. ON LOWEST SETTINGS.
This is just a completely shattering experience for me, could someone please help.

Edit: tried out fortnite again, only getting 100-120 fps with everything low, and the GPU utilization is steady over 70%. What could this mean?

My specs are:
Ryzen 5 2600x
Vega 64 sapphire limited limited edition (reference)
16gb ddr4

 

[COLGeek]

What make/model power supply (a.k.a., PSU) are you using?

 

[Niels_7]

It's a Circle 750 W modular PSU.

 

[COLGeek]

Assuming the Vega 64 is working properly, I suspect that your PSU (questionable quality) is not providing sufficient power to the GPU.

https://www.amd.com/en/products/graphics/radeon-rx-vega-64

Are you overclocking anything (CPU, GPU, memory)? If so, stop and revert to stock settings.

Are the fans on your Vega 64 free from all dust and debris?

 

[Niels_7]

I undervolted the GPU, so yes, it is overclocked. The ans are completely clean and run smoothly. Ill revert to stock settings and try again now. Perhaps it is the PSU, but shouldn't 750 watts be more than enough? Anyway, wouldn't insufficient power result in different problems such as shutdowns and the like?

 

[COLGeek]

750w should be enough, if the PSU is actually producing that much power. Lower quality PSUs often produce less power than advertised and your Vega 64 is certainly putting a load on the model you have.

Others have had similar issues as you describe when they changed Wattman settings with the Vega. Run stock and see if it stabilizes.

 

[Niels_7]

750w should be enough, if the PSU is actually producing that much power. Lower quality PSUs often produce less power than advertised and your Vega 64 is certainly putting a load on the model you have.

Others have had similar issues as you describe when they changed Wattman settings with the Vega. Run stock and see if it stabilizes.

Stabilsation is not my issue. I get slightly better performance when manually undervolting, but still nothing compared to what I should be getting. Both settings are stable though, my only worry is why it's under performing so badly. I will try and plug it into a friend's PC, see if that makes a difference, if not, oh well. Thanks for all the help!