Intel 2 Duo T8300 EC80577GG0563M User Manual

Datasheet

73

The processor requires a thermal solution to maintain temperatures within operating 

limits as set forth in 

Operating the processor outside these operating limits may result in permanent 

damage to the processor and potentially other components in the system.

The processor incorporates three methods of monitoring die temperature: 

• Thermal  diode
• Intel Thermal Monitor
• Digital thermal sensor

The Intel Thermal Monitor (detailed in 

) must be used to determine when 

the maximum specified processor junction temperature has been reached.

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, in principle one can use these parameters to calculate silicon 

temperature values. For older silicon process technologies it was 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.

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

to this new, highly-advanced processor technology, it is no longer possible to model the 

substrate transistor as a simple diode. To accurately calculate silicon temperature one 

must 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 on Santa Rosa platforms 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 taken 

into account 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).

 provide the diode interface and transistor model specifications.

THERMDA

A24

Thermal diode anode

THERMDC

B25

Thermal diode cathode