The highest representable temperature is the processor's Maximum Junction Temperature (Tjmax). You can determine your processor's Tjmax by reading the IA32 Temperature Target Model-Specific Register (MSR). The Tjmax temperature (in degrees Celsius) is found in bits 16-23 of the value returned.
If the temperature of the processor goes above Tjmax, the reading will continue to be Tjmax. That is, if you processor's Tjmax is, for example, 100c and the processor's current temperature is actually 105c, then the readings returned will still be 100c. At any temperature above Tjmax, the performance of the processor will be throttled to protect the processor from thermal overrun. If the temperature should continue to rise, however, it will eventually hit the ThermTrip threshold and the processor will be powered off. Intel does not publish what the ThermTrip threshold actually is, however, so I cannot give you a number.
In Desktop and Server processors, there is an additional threshold, called the Control Temperature (Tcontrol), that is also provided in the IA32 Temperature Target MSR data (in bits 8-15, as an offset below Tjmax). This is the temperature level that, if maintained (kept at or below), guarantees that your processor will never suffer any thermals-related silicon degradation. By definition, in the absence of full knowledge of your processor's Thermal Load Line, your fan speed control programming is required to ensure that the processor cooling fan (or blower or pump) is running at 100% duty cycle (i.e. full speed) if the temperature is above the Tcontrol threshold. If your processor's Tcontrol was, say, 85c, then you could run the processor at 85c constantly, for its entire warranted lifetime, without suffering any thermals-related silicon degradation.
In most Mobile and Embedded processors, no Tcontrol value is provided (i.e. the offset in the MSR is set to zero). This is unfortunate. It means that the only value you have to work with is Tjmax. I suggest that you use a non-zero Tcontrol value. In the 4th generation WY NUCs, which also used an Embedded processor (Core i5-4250u), we did a lot of testing and eventually concluded that we would use a Tcontrol offset of 17 in our default fan speed control programming. That is, if your processor's Tjmax was 100c, we used a Tcontrol of 83c. You don't have to be this conservative, but I don't recommend that you use zero (i.e. allow the temperature to rise to Tjmax all the time).
Hope this helps,
Hi, I have the same processor and as I've already mentioned here my CPU downclocks to base frequency 2.49 GHz when it reaches 80°C while gaming. I wonder if your processor does the same? You could test it with Intel XTU and we could compare the results.
Otherwise the temperature on my i5-7200U is around 45°C when idle.