Intel Pentium D 940 HH80553PG0884M User Manual

88

Regardless of whether or not Thermal Monitor is enabled, in the event of a catastrophic 

cooling failure, the processor will automatically shut down when the silicon has reached 

an elevated temperature (refer to the THERMTRIP# definition in 

). At this 

point, the FSB signal THERMTRIP# will go active and stay active as described in 

. THERMTRIP# activation is independent of processor activity and does not 

generate any bus cycles.

T

CONTROL

 is a temperature specification based on a temperature reading from the 

thermal diode. The value for T

CONTROL

 will be calibrated in manufacturing and 

configured for each processor. When T

DIODE

 is above T

CONTROL

 then T

C

 must be at or 

below T

C-MAX

 as defined by the thermal profile in 

; otherwise, 

the processor temperature can be maintained at T

CONTROL

 (or lower) as measured by 

the thermal diode.

The purpose of this feature is to support acoustic optimization through fan speed 

control. Contact your Intel representative for further details and documentation.

The processor incorporates an on-die PNP transistor whose base emitter junction is 

used as a thermal "diode", with its collector shorted to Ground. A thermal sensor 

located on the system board may monitor the die temperature of the processor for 

thermal management and fan speed control. 

, 

provide the "diode" parameter and interface specifications. Two different sets of "diode" 

parameters are listed in 

. The Diode Model parameters (

) apply 

to traditional thermal sensors that use the Diode Equation to determine the processor 

temperature. Transistor Model parameters (

) have been added to support 

thermal sensors that use the transistor equation method. The Transistor Model may 

provide more accurate temperature measurements when the diode ideality factor is 

closer to the maximum or minimum limits. This thermal "diode" is separate from the 

Thermal Monitor's thermal sensor and cannot be used to predict the behavior of the 

Thermal Monitor. 

NOTES:
1.

Intel does not support or recommend operation of the thermal diode under reverse bias.

2.

Characterized across a range of 50 – 80 °C.

3.

Not 100% tested. Specified by design characterization.

4.

The ideality factor, n, represents the deviation from ideal diode behavior as exemplified by 
the diode equation:

I

FW

 = I

S

 * (e 

qV

D

/nkT

 –1)

where I

S

 = saturation current, q = electronic charge, V

D

 = voltage across the diode, k = Boltzmann 

Constant, and T = absolute temperature (Kelvin).

I

FW

Forward Bias Current

5

—

200

µA

1

n

Diode Ideality Factor

1.000

1.009

1.050

—

2, 3, 4

R

T

Series Resistance

2.79

4.52

6.24

Ω

2, 3, 5