Computer: Ryzen 7 3700X, MSI - B450 TOMAHAWK MAX , G.SKILL,V Series, F4-3200C16D-32GVR, M2, Samsung 970 EVO Plus Series,SSD 2 TB, XFX RX590 Fatboy,EVGA PSU 650 GA, 220-GA-0650-X1 ,Windows 10 updated.
I picked up a used RX 590 about 2 months ago for a good price and installed it in my main PC. My previous GPU was a RX480 with a 8 pin power connector but the RX590 Fatboy has an 8+6 pin connector. I was using one modular cable from the PSU marked VGA1 with both an 8 pin and a 6 pin to the RX590 and it worked OK but seemed under-powered when I ran the Heaven benchmark. Saw a story about powering your GPU with two cables from the PSU for maximum performance. I got my EVG PSU box out and got the the other cable marked VGA and plugged in the VGA2 on the PSU and plugged it in to the 6 pin socket on the card. Turned the PSU back on and started up the computer and booted up fine. Went into the Heaven benchmark program and after about 3 min the computer died and won't come back on! After unhooking the EVGA PSU I tried another power supply and was able to get my PC operating again. I tried the EVGA PSU and it worked also with CPU cable,24pin and the one from VGA1 to the video card.Ran Heaven benchmark and it completed. Hooked the VGA2 cable to the 6 pin side ran the benchmark and it died again! Is there something wrong with my power supply?? (my test PSU only has one VGA/PCIE cable so I was unable to test with two cables to the card)

ty_ger07
Sounds like you need a power supply with a higher capacity.

I would have to agree. Right now EVGA has some great sales on PSUs

You said earlier that your card felt underpowered. What do you mean "no issues"?
You gave it better power for the card to work properly, then the power supply shut off.
It sounds to me like the card needs more power, but your power supply is being overloaded because it isn't able to provide enough.
I would buy a power supply with a higher power rating. Good sales have been going on.

Wally84
Turns out for it to work you have to use the 6+2 pin in the 8 Pin socket and 8 Pin to dual 8-6 pin in the 6 pin socket.

I disagree.
Sounds like a defect or an indication of another issue.

All I know is that when I use the 6+2 pin in the 8 Pin GPU socket and 8 Pin to dual 8-6 pin in the 6 pin GPU  socket it runs fine on every stress test I have tried. Only other thing I can think of is the cables might have been wired different at the factory. All cables came out of the original Box.

Wally84
Do you think it needs a bigger PSU?

Yes

I would agree that a higher wattage PSU would be what I would be doing. I also always use two different PSU cables to the video card instead of using two connectors that split off of the same cable.

Ended up being the card, XFX Fatboy rx590 failing, must have developed a partial short then a complete short because I tried it in another computer and it wouldn't allow it to come on at all! Now it is just a big paperweight!

I replaced the RX 590 fat-boy with a RX480 that I had in it before. I did some research and found the RX6600XT is a viable upgrade in my price range. The performance of the RX590 wasn't much different than the RX480. Waiting to see if the RX 6600XT will come down in price a little more!  I found quite a bit of online complaints  about the XFX RX590 Fat-boy failing with other people!