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

[fgw]

So why I have still 2-3 C to Tjunction but CPU started already?

first of all, on desktop and server processors the reference point used is not tjunction but tcc (thermal control circuit) activation temperature instead! tjunction is used on mobile processors only.
i know coretemp is calling this reference temperature tjunction on all processors. tat does the same, but as tat is designed for mobile processors only it is naming this reference temperature correct. guess thats the reason many people call this reference point tjcunction.
anyway, this does not change anything in the resulting temperatures ...

so why have you seen throttling starting at a coretemp reading of 83C? coretemp uses a sample rate of 1 second by default. the last time coretemp read the dts value coretemp might have read 2C and thus calculated 83C absolute temperature, but as dts and tcc reacts very fast it started throttling even before coretemp was able to read the next dts value a second later.
you can try to set the temperature read interval in coretemp to a lower value and you might see different temperatures where throttling starts.

besides that, the temperature where tcc gets activated is calibrated during manufacturing on a per part basis and thus might differ from processor to processor. regardless of coretemp, which will read anything near 85C or near 100C (depending on the assumed reference temperature), your processor might start throttling at 83C, 84C or even 87C. you simply cant tell, cause its impossible to convert dts readings into an absolute temperature.

thats the reason i requested the display of plain dts values through coretemp. which was implemented in coretemp095. instead of trying to keep your processor below a certain temperature you should try to keep dts readings ABOVE a certain value which means staying away from tcc activation by this value.

Who says that the real Tjuncton isn't at 75C ?(at this temp +- (i don't remember for sure)reported from Tcase diode.)

there is no tcase diode in c2d processors! the td (thermal diode) you are referring is like the dts (digital thermal sensor) located on the die itself and thus reports processor temperature directly from the die. the dts has a smaller foot print than the td and thus can be located closer to hotspots on the die. also dts reacts very fast and dts temperatures can be read directly as a 7bit value from a register. in contrast td needs two pins on the processor socket where an electric signal can be measured which needs to be calibrated and converted into a temperature! thus accuracy of temperature readings via td rely on calibration ond conversion. as this is done in bios, its up to the bios what temperatures are read via td. the bios might calibrate this temp to simulate a temperature similar to tcase definitions by intel or it might be calibrated to simulate a temperature which is close to core temperatures. you simply don't know what the bios writer had in mind.

regarding tcase:
intel defines tcase as the temperature measured at the geometric center of the ihs on top of the ihs surface! there is no temperature sensor nor a diode reporting this temperatur. it's just a place outside the processor where temperatures may be measured ...

CoreTemp still calculates with report point 85C which isn't the real Tjunction.

And if..

DTS readings (from CoreTemp)in my case are wrong.
I tested.
Its just the reverse

as dts temperatures are an offset to tcc activation, coretemp as all other software using dts has to calculate absolute temperatures by subtracting dts readings from tcc activation temperature. the problem here is this tcc activation temperature, as mentioned above, is different from part to part and once configured during manufacturing can't be changed nor read out by any software! this tcc activation temperature simply has to be assumed somehow!
on mobile processors a bit in a register exists which tells if tjunction (which is used on mobile processors only) is at 85C or at 100C.
this bit is NOT valid on desktop and server processors. depending on the content of this single bit, temp monitoring software assumes if 85C or 100C has to be used in subsequent calculations. this assumption might be close to reality on many processors, but definitely is about 15C off on some other processors.

DTS readings are always 99% percent accurate and should not be questioned

yes, DTS readings are correct! the problem is in the conversion into absolute temperature values as explained above. here comes inaccuracy into play ...