It is important to mention that is considered as overheating when the processor temperature reaches 95C or more. After the 100C the processor will turn off the system as a security feature.
The normal load of the processor will have the processor between the 40 and 65C and when running a task it can reach the 77C.
Based on your description, it seems that the temperature your system is getting Is normal. However, I would recommend you the following:
- Make sure there is enough air flow inside the case.
- Renew the processor thermal paste.
- Take the board outside of the chassis for testing purposes.
- Update the bios in your system.
- Make sure the CPU fan is connected to the CPU header and not the rear header.
All that you mention i've already done. But if you say that temperatures are normal, I think it can be use the computer a little bit more rude to see if can handle the heavy work.
Thank you for answering.