75C is fine, the CPU will throttle in order to avoid max temps. This isn't something that should cause instability.
It's POSSIBLE that this is a bug that's fixed with a microcode update, see here for installing it: https://wiki.archlinux.org/title/Microcode
TL;DR:
- Install
amd-ucode
- Edit
/etc/mkinitcpio.conf
, addmicrocode
afterautodetect
sudo mkinitcpio -P
reboot
If that doesn't fix it, and it crashes in Windows too, it may be a hardware problem. There isn't much you need to do in order to get a CPU working.
Yup, just reboot to apply it.
It'll show up in dmesg: "microcode updated early to Rev. ###' etc