What's my real CPU temperature?

In the screenshot, you will see the CPU temps from 3 app.'s - HWMonitor, HWInfo32, RealTemp. This is on my Ideapad netbook (see sig below). All 3 applications show different temperature readings for the CPU. Whats happening here? which one is the real reading?

Any help pls?

Cheers.

 

I would say HWMonitor is the right temp, as the others I don't think have the right TJ max set. The TJ max should be set at 100C.

 

Thanks.
Although i had to set the TJMax to 105 in RealTemp to get the same value as Monitor.

 

Check w/ RealTemp.

 

And you could add CoreTemp to the mix and see what numbers you get from that

 

I'd say neither of them is correct
And the reason is the implementation of the DTS CPU sensor - on many CPUs (prior to Nehalem family) they provide accurate reading only at highest temps around Tj,max. Those sensors have been obviously designed only to catch the hottest temp to engage throttling. When the temp is lower there's a large inaccuracy of +-15 degrees C (by design). There are certain CPU families (like your Atom) where when the temperature reaches 50 C (saturates) or lower the inaccuracy is sooo big, that you can't use the reading as a real value ! Intel says: " A value below 50 C means that the temperature is < 50 C only and not a specific temperature". It simply will never help to get/set any Tj,max since the sensor device is unreliable at lower ranges.
Even for some post-Nehalem CPUs (like Gulftown) the DTS sensors might be very unreliable (by design/implementation).
According to several documents I studied, the best accuracy with DTS you can get is about +- 5 C (uniform).
This is a fact that ! I'd like spread this information to as many users as possible, since most of them don't realize this fact (and play with unreliable numbers) !

 

In my experience, RealTemp has a higher chance of being accurate.
It automatically compensates for TJ values whereas HWMonitor has a fixed one.
The latter showed 10 deg C higher temps on my cpu because it failed to take into account my TJ was 90 and not 100 where RealTemp was fine.

 

How do i find out what the TJ for my netbook is?

Oh, and whats the difference between RealTemp & RealTempGT?

 

Depends on CPU. Nehalem and later ones have the Tj,max written in a MSR register (0x1A2). That's fine..
However, for CPUs prior to Nehalem (Core 2, etc) it's almost impossible to determine the true Tj,max. Although Intel has published some numbers for certain families, it has been proven that many of them are not correct. Various ppl have performed extensive experiments to determine more accurate values. However those CPUs can have different Tj,max set even for same models (depends during manufacturing). So in many cases for pre-Nehalem CPUs it's a pure guessing..

 

My understanding is that 0x1A2 is the minimum temperature at which DTS will be 0. This would mean a CPU with a target temperature of 90°C and an accuracy of -10°C +5°C, the junction temperature could be anywhere from 90°C to 105°C with 100°C being the average when DTS = 0.

This would mean in the above case that the best to worst chip could have a 15°C difference at TDP. It might also explain why they don't calibrate individual values into 0x1A2.

 

Most Nehalem family chips have an uniform accuracy of +-5 C across the whole temperature range. Of course there are some exceptions like the Gulftown which has a quite bad DTS.