Where exactly is CPU temperature being measured?

As noted in the section on monitoring main sensors, the individual sensor equipment of Macintosh computers can be very different depending on model type. To ensure ease-of-use, System Monitor automatically selects a certain sensor as being typical for representing processor temperature, and this sensor can be shown in the menu bar. The following policy is used to determine this sensor:

1. A temperature sensor as close as possible to the processor chip will be selected. If Intel® Power Gadget is available and the user has granted System Monitor permission to use it, the chip package sensor monitored by Power Gadget will be used.
2. In case more than one processor chip is available, the first processor will be selected. For Macintosh models with numeric processor designations, this will be processor 0. Otherwise, the processor with designation A will be selected.
3. If available, the temperature diode of this processor will be selected, if not, a sensor at the heat sink of this processor. In case this sensor is unavailable as well, the proximity sensor of this processor will be used. For Macs with Apple Silicon, System Monitor tries to find the temperature sensor monitoring the first performance core of the chip package.