TJ Max is an inherently unreliable and inaccurate method of measuring idle/low temperatures. Due to the way it was designed, the readings are so inaccurate under 50C that Intel says they can only be read as a number temperature above 50C. As the temperature approaches TJ Max, the precision increases and at TJ Max the temperature is considered to be 100% accurate

TJ Max is the value that activates cpu throttling and auto shuts down the pc when Thermal Monitoring is enabled to prevent overheating of the processor... usually the distance between TJMax is measured and converted into C, lets say distance to tjmax is 50, and the tjmax of this processor is 100c, then the temp is considered 50c...

for youliang's case, he'd just have to adjust the tjmax of the processor , and if not mistaken bios only give CPU temp, not CORE temp... coretemp application reads CORE temp, based on the tjmax u set ... coretemp reads the distance between tjmax and converts to Celsius

edit: CPU temp is measured by placing a sensor on the middle of the integrated heatsink of the processor, while CORE temp is measured via digital thermal sensor, placed on each core of the processor

the only way to know the temp 100% accurate is to place a sensor directly on the processor itself , but reading CORE temp should suffice as they give u an indication when will the throttling activate, and they only activate when the processor is being overheated to its limit