How Does a Motherboard Measure CPU Temp? (E8400)


Does a modern motherboard (BIOS) measure CPU temps off the CPU itself or from a sensor underneath the CPU that acutally measures heat like a case temp gauge? I've seen the sensor before but not now on newer motherboards.

My problem is gauging the temps on my E8400. Coretemp reads the same temp at any speed when idle 59/63 and over 90c at 1.45v and 4.3Ghz. The CPU never throttles or shuts down. When I grab and feel around the heatsink it's barely warm--nothing even close to my Q6600 or E6400. Coretemp always starts off at 59/63. The temps match each other once I prime and they rise passed 63c. That would be 30 degrees more on a overclock (not like my other CPUs where it's 20c).

I've read that other people are having similar issues while some are not. So basically, is it better to watch the motherboard CPU temp sensor because it has its own sensor. Or is it too reading from the CPU diodes? EasyTune (Gigabyte) CPU temps seems a bit off too, around 75-80c on load. To me, I simply can't feel 176F in my case.
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  1. That's odd. My coretemp measures 35C idle, 55C under 100% load.

    While PC Probe (By Asus) measures 5C lower than coretemp at all times.

    Have you tried updating the Bios to see if that fixes the temp issues? I highly doubt your chip is running that hot unless your heatsink is literally falling off......

    Try finding a few other programs to see what they measure. Speedfan often measures lower than normal, but maybe try it?
  2. As I research, it seems the temp reading problem is within the E8400 itself. People are having similar problems with different boards. One had an identical problem as mine too.

    I have updated my P35-DQ6 BIOS, but the newest one makes my CPU fan spin at full blast, 2500RPM. Anyone have this problem with F7d? I'm on F7c for now.
  3. There are 2 temperature sensors in the Core 2 Duo processors. One is an analog device called the thermal Diode. The new one is the Digital Diode that works with the new PECI interface. If the board is trying to work with the Thermal diode for the Wolfdale processor ie(E8500, E8400) then there will be a problem. Intel states that they must work with the PECI interface to work with the Digital diode. The Diode does work correctly. The motherboard/bios/software is the one at fault.
  4. beurling said:

    Speedfan often measures lower than normal, but maybe try it?

    It does??!?!?! My laptop runs 180F + on even 80% load. And it measures low? My god my laptop could ctach on fire somday
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