The readings from each core come from within the silicon die, each core has a thermal sensor on the chip. I think the other reading depends on your motherboard. HWMonitor doesn't show my "CPU temp" as such, the reading that my motherboard's included app reports as CPU temp is listed as TMPIN1 on HWMonitor. I think it is a sensor mounted on the motherboard under the CPU but I could be wrong, the sensor may be on the chip itself but it is read from the motherboard's hardware monitoring chip (not the CPU directly) which is why I'm assuming it is on the board and not the chip.
