Intel 2 Duo T6500 AW80577GG0452MA User Manual

108

Datasheet

The processor incorporates three methods of monitoring die temperature: 

• Thermal  Diode
• Intel® Thermal Monitor
• Digital Thermal Sensor

Intel’s processors utilize an SMBus thermal sensor to read back the voltage/current 

characteristics of a substrate PNP transistor. Since these characteristics are a function 

of temperature, these parameters can be used to calculate silicon temperature values. 

For older silicon process technologies, it is possible to simplify the voltage/current and 

temperature relationships by treating the substrate transistor as though it were a 

simple diffusion diode. In this case, the assumption is that the beta of the transistor 

does not impact the calculated temperature values. The resultant “diode” model 

essentially predicts a quasi linear relationship between the base/emitter voltage 

differential of the PNP transistor and the applied temperature (one of the 

proportionality constants in this relationship is processor specific, and is known as the 

diode ideality factor). Realization of this relationship is accomplished with the SMBus 

thermal sensor that is connected to the transistor.

The processor, however, is built on Intel’s advanced 45-nm processor technology. Due 

to this new processor technology, it is no longer possible to model the substrate 

transistor as a simple diode. To accurately calculate silicon temperature use a full bi-

polar junction transistor-type model. In this model, the voltage/current and 

temperature characteristics include an additional process dependant parameter which 

is known as the transistor “beta”. System designers should be aware that the current 

thermal sensors may not be configured to account for “beta” and should work with their 

SMB thermal sensor vendors to ensure they have a part capable of reading the thermal 

diode in BJT model.

Offset between the thermal diode-based temperature reading and the Intel Thermal 

Monitor reading may be characterized using the Intel Thermal Monitor’s Automatic 

mode activation of the thermal control circuit. This temperature offset must be 

considered when using the processor thermal diode to implement power management 

events. This offset is different than the diode Toffset value programmed into the 

processor Model-Specific Register (MSR).

 and 

 provide the diode interface and transistor model specifications.

THERMDA

A24

Thermal diode anode

THERMDC

A25

Thermal diode cathode