Sultan.of.swing
Sounds more like a power supply issue.

The HX850i is on the known good list - though it's possible that it has aged and is not delivering the same power that it was (or the PSU is getting too hot and shutting off (bad PSU fan/fan blocked from getting air in)).
 
As to the OP - try setting the temperature slider to max. It raises the power slider too, but the temp goes to 91 instead of 83. You can always set a more aggressive fan curve as well, to keep the temps lower.

I'm overclocked to 5.1ghz on a 10900k and using an Asus tuf 3090. Autocad and extremely heavy rendering via v-ray and revit. I've been working 9 hours striaght and the weekend I ran flight sim 2020 maxed out for 6 hours and I have yet to experience any issue with the GPU. In my living room I have a 65" 4k samsung. In my office I have a 43" pg43uq driving at 144hz via displayport. My power supply is an evega 1600watt titanium. Yes I know I don't need a 1600w but it was on sale for the same price as a 1000 watt gold. If I were you I would try a different psu for testing. Also do you have custom modded cables? I have found that sometimes with custom cables the gauge is slightly smaller than stock on specific conductors and all it takes is a gauge smaller or a bad pin crimp connection and you will build resistance. It may appear power is okay but you won't see that in watts. It would be in amps. After the pc reboots shut it down and really feel the gpu cables and make sure they do not feel hot.

I swear the very first thing I did was install the latest Nvidia drivers. But somehow they didn't stick. I installed them again, and now most everything is fine, except for my embarrassment. I did an overnight test of AC:Odyssey where the camera was just spinning. Temps on the GPU were stable at 68C. PSU was level at 515W (when actively playing I've seen a peak of 560W). Corsair is fantastic and my last set lasted a decade. My HX850i is barely a year old.
 
That said, my big mistake in testing was that I kept looking at No Mans Sky. It just crashes like crazy (freezing up). Usually within a couple minutes of firing it up. So I guess there is something else going on there. (Maybe Gsync related)... or just a bug in the game code. It didn't crash at all with the 2080 Ti. It's the game I've been actively playing. 
 
At least all my firmware is updated and Windows 10 is now on winver 2004, which was a major windows update.
 

Hey all I have a 55CX with a 3080 so hopefully you all can help me out. I have been noticing some minor artifacts if I go over 100 fps. If I set a limiter for 100 fps everything is all good. I did apply the LG 3.11.25 firmware update manually and everything works fine, no flickering or black screen, GYSNC working. But for the life of me I get annoying micro vertical artifacts showing when I'm gaming over 100fps. All my setting Windows are set for refresh rate of 120 same goes for NVIDAI CONTROL PANEL. I have tried everything from having vsync on/off but I can't seem to go over 100fps without noticing those artifacts? could I have a bad card? My temps are fine within 50-60 degree, using all 3 PCIE power so power is not issue. I tried playing with OC setting plus just stock setting still the same. Games I have seen it are in Wolfenstein New Collosus, Metro Exodus and DOOM. So if anyone have these games can you  play 4k while playing at 120fps?  Could it be my hdmi cable? I play Destiny 2 and I'm getting over 120fps 4k max settings no issues, so any help is welcome thank you. Also notice if HDR is not on these 3 games work fine. But Destiny 2 has HDR and is working fine, so I'm stump. 
 
Edit:
I reseated my card made sure it was very sturdy and connected, seems to be fine now as well. False Alarm

Happy to report that I installed version 5.00.03 on my LG E9 via USB, and now it works flawlessly in 4k12hz + HDR + G sync. Very easy to update using a USB stick and the download from this link for C9 and E9 models
 
https://www.avsforum.com/.../page-52#post-60188535
 
 
EDIT: I am using this 16' cable 
https://www.amazon.com/gp...itle?ie=UTF8&psc=1

So I think I resolved my stability issues... I bought a HX1200i to replace the HX850i -- the 850 is only a year old and is likely just fine. When I took it out, instead of using a single cable to power both GPU slots, I used two separate cables. Maybe that would have fixed my original problem? I only have a couple hours of stability since the swap -- so I'll need to game some more. My biggest power spike at stock card settings is 576W paired to a 9900K. My leading theory is that the 3090 has wild mood swings and even a rated power supply might not be able to adapt fast enough. Hard to say without more testing....

In any case, the 2080 Ti never had issues being connected to the 850 with a single cable (two 6+2 pins, one cable) though it draws less power. 
 
Also these are the cables I'm using without issue: https://www.amazon.com/Cable-Matters-3-Pack-48Gbps-Support/dp/B081NXV3ZR (I nearly returned them before realizing the Instant Game Response was responsible for the black flicker -- though it's completely gone now and it's always on. So no idea what changed).

morness
Also these are the cables I'm using without issue: https://www.amazon.com/Cable-Matters-3-Pack-48Gbps-Support/dp/B081NXV3ZR (I nearly returned them before realizing the Instant Game Response was responsible for the black flicker -- though it's completely gone now and it's always on. So no idea what changed).

Fire up a game with NV control panel running to make sure that the TV keeps gsync enabled once the game is running. If so then you're good to go. :)

One more tip - I've been having issues coming out of sleep, and I believe I narrowed it down to Philips Hue Sync app causing the issues.   I discovered this while trying to watch a video with light sync and it crashed my PC one time, tried a different video and it was in a bad black flicker, tried a few more times in different apps and video content and continued to get crashes, reboots, flickers, total loss of video signal.
 
for those not familiar with this app - it uses your video & audio signal to control Hue bulbs and adds the ambient room lighting.  it injects itself in  the signal stream like an overlay.
 
I've now uninstalled Philips Hue Sync and for the first day in weeks my PC woke out of deep sleep.  I think philips is aware of issues because they rarely update this app and over the past two weeks they had 3 updates.. latest version came yesterday made things worse and that sparked my thought to test and remove it.

Update to confirm for those that may be interested: I'm using the 3m cable from Zeskit mentioned earlier in the thread with no issues at all up to 120Hz on my LG CX65 & 3090 FTW Ultra. (latest hotfix drivers, manually set the profile/resolution/refresh, latest XOC BIOS on the 3090)
 
https://www.amazon.com/gp..._s00?ie=UTF8&psc=1

I have HUE as well, but I never hooked it up to my PC -- I just use Alexa voice commands to drive it. I found that the software on HUE is pretty bad (and SLOW). Btw, my GSYNC is on all the time -- I have it set for both windowed mode and full screen mode. I like to play games in borderless window so I can multitask other things. I had a lot of issues with full screen on the LG (via HDMI)... especially when you are playing at lower resolutions which is what I was doing with the 2080 Ti before I got the 3090. Now it's less of an issue because I play at 4K in everything.