Question Stress Test shutdowns issue

[naptin]

First of all I am sorry for my lame English. Here is the system specs:
GIGABYTE Z390I AORUS PRO WIFI ° 16 GB DDR4 3000Mhz ° Intel i5-9600K ° WD 500 GB Blue M2VM SSD ° Intel HD 630 IGPU

During a heavy work the Pc was shutting down and clear (reset) CMOS. After that I have to wait some time to turn on again. It sounds like a cpu heat issue I know but when I check manually (with hand) or from BIOS everything seems cool. (BIOS says 45 C only)

but resetting the CMOS values are really weird.

any idea?

 

[popatim]

Power supply issue with a dead/weak cmos battery would do that too. PSU's aren't really off anymore so you don't spot a cmos battery issue right away like in the old days.

 

[naptin]

I changed power supply with a really strong one but it is still same.