H310M/M.2 Bios Reporting Incorrect CPU Temperature

The UEFI is not an operating system, the operating system is optimized and refined to utilize the system's resources in an efficient manner. The size restriction of a ROM chip prevents such optimizations. In the UEFI so there is no multi-threading or code optimization beyond the most basic. This means that everything it does is performed on a single core and all it's functions are permanently active, there is no "idle" code that turns off a process when it isn't in use. Consider the amount of functions in the UEFI and how it needs to access the system. I would be surprised if the core it uses is ever under 90% utilized.

It's a fascinating topic, sadly that is as far as my own investigation into the matter went. Much like yourself, when I was first exposed to the UEFI I had the same question about temps. It took a lot of digging to uncover the why and how. I hope that answers your question. It's always nice to see another inquisitive mind that wants more than "that's just how it works"

The BIOS does not report idle temps, the CPU is under load while in the UEFI. It is a common misconception that UEFI temp readings are idle temps, this may have been closer to the truth with the BIOS systems of the past but UEFI is a different animal. Even in old BIOS based systems the reading was not a true idle temp but the load the BIOS placed on the CPU was minuscule compared to modern UEFI.

I hope this clears things up for you