Question Still got it. Troubleshooting Powercolor Hellhound 7900XT

[Paratus]

Thought I would share this issue and solution I found installing a brand new Powercolor Hellhound Radeon 7900XT

After installing the new card and fighting with Win10 to install the correct drivers I checked out some games.

It would launch and run games fine, (briefly checked Skyrim, Doom Eternal, Baldurs Gate 3). However it would repeatedly hard crash the PC when trying to run a 3DMark Timespy benchmark at the same point, about 10 seconds in.

Specs
CPU: Threadripper 2950X
MOBO: MSI x399 Gaming Pro Carbon
RAM: 32GB G-Skill DDR4-3200mhz
PSU: Corsair RM850i 850w Gold

By hard crash, I mean the PC shut down and only cycling the power supply would let it boot. That gave me the clue that it was probably power delivery related. Most likely the GPU was dragging down the voltage and triggering undervoltage protection when the benchmark highly loaded the GPU. I tried using the “Quiet” lower power GPU BIOS but still a hard crash.

Was I overloading my PSU?

Powercolor recommends a 750W PSU. A 2950x pulls about 180W and the 7900XT pulls 300-350W leaving me over 300W for my SSDs and case fans. So I should have been good with an 850W PSU.

What I wasn’t good with was the RM850i can be set to either single rail or multiple rail modes. It defaults to multiple rail. In multiple rail mode it limits the amperage available to each PCIe power connector. So unless specifically using 2 8pin PCI power connectors from two separate cables from separate rails the PSU can only supply a portion of the available amperage to the GPU.

The way I had it setup I was only using a single power cable since it provides 2 8pin connectors. That single cable only pulls from the one rail. In multiple rail mode that was enough amps for my old Red Devil Vega 56 but not the 7900XT.

Using the included Corsair power supply utility I was able to set it to single rail mode. Now the entire 70A is available through the single PCIe cable . 3dmark can complete a run successfully now.

 

[biostud]

My 6800XT also crashes in Timespy 10 secs in, just a throws an error though.
Otherwise it works fine.

 

[Paratus]

My 6800XT also crashes in Timespy 10 secs in, just a throws an error though.
Otherwise it works fine.

Might be power related. Just sayin.

 

[DAPUNISHER]

It is recommended to use separate cables. But I won't give you any grief about it -

 

[Paratus]

It is recommended to use separate cables. But I won't give you any grief about it -

It’s a good idea. Now I have to remember where I kept all the spare modular cables….

 

[Brainonska511]

It is recommended to use separate cables. But I won't give you any grief about it -

I have my Hellhound 7800 XT on a single cable running from my Corsair RM750e. It has had no problems so far, but that's also likely thanks to Corsair using properly gauged cables for cables with pigtails connectors. (Also helps that this supply is single rail, so I wouldn't have an issue the OP noted).

 

[Shmee]

Good that you figured it out. A while back, when I had a 1250W Seasonic in a system with CF R9 Fury cards, the system would randomly shut off during games. Turned out there was a bulged capacitor in the PSU that I could see, so I RMA'd it. Seasonic support was pretty good.