I have the 3090 FTW3 Ultra paired with a EVGA 850W GA.
 
I have not experienced any shutdowns or restarts. I have not updated my bios to anything but enabled to OC switch. I've done some overclocking with a stable 120+ Core / 1000+ Mem. Highest I've seen was 453W.
 
Even with that, no issues have yet been discovered. I'll let you folks know when it does happen.

JimboBolbi
I have the 3090 FTW3 Ultra paired with a EVGA 850W GA.
 
I have not experienced any shutdowns or restarts. I have not updated my bios to anything but enabled to OC switch. I've done some overclocking with a stable 120+ Core / 1000+ Mem. Highest I've seen was 453W.
 
Even with that, no issues have yet been discovered. I'll let you folks know when it does happen.

What CPU are you running?  I had no issues with my i7 6700k but ran into shutdown issues once I upgraded to the Ryzen 9 5900x. 

dryja123

JimboBolbi
I have the 3090 FTW3 Ultra paired with a EVGA 850W GA.
 
I have not experienced any shutdowns or restarts. I have not updated my bios to anything but enabled to OC switch. I've done some overclocking with a stable 120+ Core / 1000+ Mem. Highest I've seen was 453W.
 
Even with that, no issues have yet been discovered. I'll let you folks know when it does happen.

What CPU are you running?  I had no issues with my i7 6700k but ran into shutdown issues once I upgraded to the Ryzen 9 5900x. 

I'm using the 3900X @ 4.3GHz. Since day one release of the 3090, I haven't really experienced any issues.

I have a Corsair RM1000X. I get shutdowns (and eventual restarts) unless I downclock the card slightly. My system usage during gaming minus the GPU is around 200-250 watts. While it COULD be a bad PSU, I'm wondering if something else is up here with so many people having issues. The voltages for all my connectors are in spec.
 
Looking at that graph in a previous post, it looks like the GPU has spikes that can exceed 600 watts. I am wondering if maybe there is a peak above that for certain cards. In my case, it sounds like a PSU auto shutoff trigger. I've been trying to get some solid logging going on, but with the system shutting down so abruptly it makes it impossible to see what the total power draw is when the shutdown happens.

Can I underclock my EVGA FTW3 Ultra to prevent this? Just to keep it from happening until I get a new PSU through RMA or other channel? If so, does anyone know how low we have to go?

I have a 6 or 7 year old 750W G2. No card yet since I have no luck at queues, but hopefully I don't run into the issues you guys are having. 

I'm having this problem now too. My corsair RMX 850 is about 5 years old. I get the random restarts and its making rage..... I started a support ticket with corsair and evga.. just waiting for a response. I hope corsair will rma me a newer psu.

Shrilla
I have a 6 or 7 year old 750W G2. No card yet since I have no luck at queues, but hopefully I don't run into the issues you guys are having. 

I had a 6 month old AG750w Gold and it wasn't enough, but now way to know until you try it

Im running in to similar issues with my 3090 FTW3 Ultra Hybrid, paired with an i7-7700k and a Seasonic Snowsilent 750w Platinum.
 
Timespy runs without any issues, when playing Cyberpunk the PC will shut down and restart after about 45-90min.
 
Stresstesting with OCCT causes a restart after only 1-2min, so i guess my PSU is the culprit.
 
I knew that 750w was the bare minimum, but i wanted to try first. 
 
Seasonic Prime 1300w Platinum is on the way now, will update as soon as i have it in my rig.
 

I overclocked the 3900x and the 3090 Hybrid XC3, and when I started to play Cyberpunk, shutdown! I dialed back the overclocks and it works fine now. The 750W PSU just isn't enough. Its only a year old.