I’m not 100% sure on the 850. I had an OC’d 3080ti and a 5950 with PBO enabled randomly rebooting on a Seasonic 750w Plat. I jumped up to a 1000w PS, so I can’t directly say if 850 would have been enough, but the line was somewhere between 750 and 1000.
We had a similar issue with a 10900K and a RX5700XT - at full (power virus) tilt, the system would reboot with a Seasonic-built Phanteks 750W unit. This was while respec'ing the case review rig, and the load was designed to test case cooling.
I briefly used a refurb Corsair 850W TX unit (not fully modular, basically entry-level) without issue, before upgrading to the final Seasonic 1000W Gold unit. A second example is my own; with a 12700K and a 3080 12GB FTW3 (EVGA's 450W board for that GPU SKU), I was able to get an 850W Corsair RX Gold unit to start complaining but did not experience instability.
That's personal experience with 750W, 850W, and 1000W units with power virus loads, but I'll say that the math also adds up: once you pull 300W through the CPU socket and 450W through the GPU, well, you're at 750W, and you still have the motherboard, storage, RAM, fans, RGB lighting, USB peripherals, and whatever else loading the PSU.
So that's how I get to the '850W is enough' determination, since your average user shouldn't be running simultaneous power virus loads, and how I get to '1000W and be done' for folks that are a little too adventurous for their own good
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(and that assuming that they're using top-shelf parts - a recent upgrade I did for a buddy who had a ~5 year old system didn't even consider the PSU used, since power draw went down!)