@
Rykane
i have seen a lot complains about random restarts lately but never i have seen an in-depth troubleshooting process like what you are doing and most importantly detailed reporting of everything you do and the results you get back here, you have my thanks, respect, and sympathy, and above all my best wishes that you get this issue resolved ASAP!
i myself are having this random restart thing, granted to a lesser extent than what you are facing, its just so rarely happens with me that it has not yet affected my gaming or pc usage negatively (but still so annoying and unacceptable nevertheless), it happened about maybe 5-6 times in 1 month but only happened after my last upgrade which involved new RAM kits, an RTX 3090 and a Ryzen 7 5800x.
at first i though its an RTX 30 thing as seemingly people with RTX 30 are the ones complaining the most, but when my cousin whom have a 6800 XT are suffering having a lot more random restarts than i am then that might not be the case, i have tested my ram kits with memtest86, prime95, aida64 overnight and they are 100% stable ZERO errors so no i dont think its the rams.
i then thought maybe its my ryzen 7 5800X (as my cousin has a ryzen 5950x) specially since i have used the curve optimizer to overclock it so i thought maybe its not stable and its causing the restarts or maybe its a ryzen 5000 thing but hey you have an intel 9900k and having the same issue! beside my 5800X have been extensively tested with every possible stress test app possible including 15 hours of prime95 blend, 8 hours of asus realbench and 6 hours of aida64 and many other tests (including some heavy AVX), it passed all of them with flying colors!
im outta ideas right now and the problem is that i can not reproduce the random restart to try to figure out whats causing it and specially in my case that it is very rare to happen.
nevertheless im having a guess which i will try and report back if it helps and i suggest you do specially that your random restarts are much more often, is your psu ocp (over current protection) single rail or multi rail? or maybe its switchable like mine is, i have heard (not sure its true but thats the idea that makes most sense at least atm) that the new RTX 30 and radeon 6800 XT/6900 XT have crazy power spikes that might trip the multi rail ocp of your psu (no matter how high wattage it is) and then the random restart happens, my guess is if we use a single rail ocp this might help with the random restarts? i do not know and im not sure its just a guess, i will switch my psu to single rail ocp and report back in a week or 2 if i do not get any random restarts, and of course will report immediately if i get one.
do us a favor @
Rykane and keep reporting back your findings and every one else help us, lets work together on reaching the bottom of this hopefully soon.