Had a VERY VERY similar problem with my system , although I have older hardware , but a close enough equivalent to possibly help your situation : My current :5900x heavy oc'd on water w/two rads w/ Sapphire 7900xtx Nitro+ , MSI x570S Tomahawk Max WiFi , 64gig 3600/16 . (Evga/Super Flower G3 850/Gold = replaced with) Seasonic Vertex 1200 watt gold
Ok , with the same above hardware (using the 850 wat), I was getting almost identical shut downs ( once in awhile just a black screen reboot) , which started to show up shortly after installing the 7900xtx . ~ Never had a problem at all with gaming or any type till some time LATER even with 7900xtx used for months . ~ Problem got progressively worse . Checked every thing (software/hardware/etc) and all that was fine and max power usage was 705 watts still leaving me some headroom , but the hard boot shut downs still happened and more frequent .~ So , I figured easiest thing to do was up the power supply and if not the problem , eh I could use the upgrade . Was going for a 1000 watt , then said go big or go home so I donrt have worry about it for my next AMD system upgrade , so I went 1200 watt , and a PSU with the newer specs . ~ BINGO ! Problem fixed with the new Seasonic ( always luved Seasonic psu's) and things have been rock solid ever since .~ My only dismay was I wanted the platinum Vertex vs the gold version , but was never available at the time of purchasing . However , the Gold version has been perfect , nice solid rails , super quite , and no problems ever since ; system has been rock solid with the Vertex .
I know the first things many go to as an easy fix and they say " its your psu" , but in this case I'd say the 1000 watt , with your 4090 and newer chipset etc is not cutting it for some reason (that 4090 draws alot and has pretty good spikes like most newer gpu's do and you know it does) .~ So I'd say go Seasonic Vertex 1200 watt Platinum (or even gold , but with a 4090 = Platinum .~ I know , the old psu gig replacement to cure all , but remember even with my current system with the 850 watt G3 , my TOP power USAGE hit barely over 700 watt (710/715)) with room to spare , but the psu ,even though a very good and solid one , just was not enough to quench the thirst of the 7900xtx Nitro+ .
Sorry for the long explanation ..........
Oh and btw , I game at 10030 x1400 with three 34" Ultrawides in EyeInfinity , no problem (NO black screens , shut downs or reboots!!! )
All the best to you , and how is that beautiful 7950x3D doing ??? Its next on my list !!!!
