Intel TAT / CoreTemp / IDCC all different temperatures....

[unclewebb]

there is only one correct temperature reading on intel core technology processors: relative temperature (dts reading) as introduced incoretemp 0.95 everything else, besides mobile processors as discussed above, is speculation!

I agree with the above statement 100% but.......

I still think that CoreTemp 0.95 which uses either a fixed 85C or 100C Tjunction value in its calculation results in a pretty accurate absolute temperature for the desktop processors.

I decided to come up with a simple test so users can determine if the absolute temperatures reported by CoreTemp are valid or not.

On my E6400, revision B2, CoreTemp 0.94, CoreTemp 0.95 and SpeedFan 4.32 all report the same temps. For this test I used SpeedFan for its graphing capabilities.

The goal is to run your processor as cool as possible. Start by opening your case. Next lower the FSB to 200 MHz, lock the cpu multiplier in the bios at 6 and reduce the core voltage. Setting core voltage to 1.200 volts or less is adequate. With my P5B Deluxe I was able to get the core down to 1.104 volts as reported by CPUz.

You can do this with any Core2Duo so this test is consistent no matter what processor you have.

I believe that when you run an air cooled processor at reduced speed and voltage in an open case, the core temperature will start to approach the ambient temperature. I used SpeedFan to keep the cpu fan at its maximum.

With a room temperature of 18C as measured with a consumer grade digital house thermometer, I ended up with a reported core temperature of 17C during this test.



In theory with air cooling you shouldn't be able to get lower than ambient temperature but if you keep in mind that both values are integer values and are at best only accurate to +/- 0.5 degrees and that my $20 Radio Shack thermometer is far from perfect then I think my results confirm that:

An air cooled C2D at 1200 MHz and 1.1 volts will put out so little heat at idle that the core temperature and the ambient temperature will be very close to equal.

For my E6400, the CoreTemp / SpeedFan assumed Tjunction value of 85C, seems to produce a very accurate absolute temperature value.

This test can be used by anyone with any Core2Duo processor to at least give them an idea if their temperature monitoring software is in the ball park or if it's totally out to lunch.