High cpu temps on custom water cooling

If you are hitting your thermal limit during R20, it is either a contact problem or a voltage issue. There isn't another possibility. The MT run takes 15-30 seconds. It isn't enough time for coolant temperature or that aspect of the system to come into play. I would get the same temps on my 10900K with a 120mm cooler as the triple 360mm I have in place. The longer you run a load, the more heat management (the cooling system) matters.

 

If you have a contact problem, CPU temps should be out of line all over. Idle, browsing, applications, testing. Usually you will see dramatic temperature shifts as the voltage is applied or drops off (if using those settings). The trickier one is where your contact is almost perfect -- not enough to be clearly noticeable, but heavy loads can push you over the edge. You would still see a small shift across all loads. Typically you need to take off the block and examine the spread to see if this is the case.

 

I can't counsel you on the voltage for AMD 3000 series, but presumably nothing has changed. Do verify the load voltage during R20. Motherboards and BIOS versions are getting complicated with fairly elaborate behavior controls. It may be adding on voltage for that specific type of load. R20 is also hot. MT produces the highest temperatures of anything I have done on a 10900K.

Voltage is perfectly stable and never changing from 1.319v as I have a good motherboard. Idle temps are all over the place pretty much between 39c-55c or so, rapidly jumping up and down all the time. Gaming temps stay between 60c-75c or so at 10%-60% loads.

A Ryzen 3000 CPU will begin thermal throttling at 85C and hard shutdown at 105C

If your CPU doesn't even reach the 85C threshold, it's 100% related to your OC.

Also, it's absolutely normal that CPU temps jump around. 75C on a continuous gaming load is a little on the high side, but totally fine. What messes you up is most likely AVX instructions from R20 that your OC cannot handle so it promptly crashes.