Why is my motherboard temperature a constant arbitrary number?

checked with Piriform Speccy.

checked with open hardware monitor

checked with hardware sensor monitor(this one shows different statistics)

Answer

Your motherboard is not at 123'c. The application is reading a sensor that does not exist, or is reading data in a format it doesn't understand properly.

Not all motherboards have the same number of sensors, and not all sensor chips have all inputs connected. Sensors that are not connected will often give imaginary readings, whether that be zero, 123'c, 65535'c or any other temperature. It is also not unknown for negative temperatures, e.g. -127'c to be reported as well for unconnected sensors. The actual value used as "null" or "no reading" is specific to the driver and sensor chip in question.

Try to update to the latest drivers in order to fix sensor detection issues: Intel NUC Kit D54250WYK