Real Temp - New temp program for Intel Core processors

[unclewebb]

Leeghoofd: The difference between CoreTemp and RealTemp for the Q6600 GO is only 5C. CoreTemp assumes TjMax=100C and RealTemp assumes TjMax=95C which is based on the testing of my Q6600 G0 with an IR thermometer.

Reported Temp = TjMax - Digital Thermal Sensor Reading

I think everyone assumed TjMax=100C because that gave believable readings at idle. Before RealTemp came along, every program blindly assumed that the temperature curve from these sensors was totally linear but none of them are. Since the first 65nm processor left the factory, the sensors have not been 100% accurate from idle to TjMax. I've seen only one mention of this by Intel in an interview at Anandtech which surfaced soon after RealTemp was released.

Intel designs and calibrates these sensors to accurately trigger thermal throttling and thermal shut down but they were never meant to be used to accurately report idle temperatures.



What I discovered was that if a user took 5 minutes to calibrate his CPU then these sensors could also be used to provide fairly accurate idle temperatures. Using the correct TjMax results in extremely accurate load temperatures. Using the wrong TjMax will help cover up the problems these sensors have at idle but by 60C, your load temperatures will be off by 5C in the case of the Q6600 G0.

On most Q6600 G0 processors, doing things the correct way or the CoreTemp way doesn't make a huge amount of difference. It seems that most of the 65nm chips read about 5C too low at idle so boosting TjMax by 5C made everything look great. On 45nm chips like my E8400 which read too high at idle, using the wrong TjMax combined with ignoring the sensor issues at idle results in reported core temperatures that are a long way off from reality.

Edit: I believe that thermal throttling starts to happen just before TjMax is reached. I've tested a few different processors and throttling has started each time at DTS=2 or 3 as reported by PROCHOT# being set in the processor. It seems to be designed by Intel to kick in at this point to help prevent the CPU from ever reaching TjMax.