Intel 640 User Guide - Page 35

Thermal Management Logic and Thermal Monitor Feature

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Thermal/Mechanical Design Guide

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For information regarding THERMTRIP#, refer to the processor datasheet and to Section 4.2.8 of

this Thermal Design Guidelines.

4.2.6

Operating System and Application Software

Considerations

The Thermal Monitor feature and its thermal control circuit work seamlessly with ACPI

compliant operating systems. The Thermal Monitor feature is transparent to application software

since the processor bus snooping, ACPI timer, and interrupts are active at all times.

4.2.7

On-Die Thermal Diode

There are two independent thermal sensing devices in the Pentium 4 processor in the 775–land

LGA package. One is the on-die thermal diode and the other is in the temperature sensor used for

the Thermal Monitor and for THERMTRIP#. The Thermal Monitor’s temperature sensor and the

on-die thermal diode are independent and physically isolated devices. Circuit constraints and

performance requirements prevent the Thermal Monitor’s temperature sensor and the on-die

thermal diode from being located at the same place on the silicon. The temperature distribution

across the die may result in significant temperature differences between the on-die thermal diode

and the Thermal Monitor’s temperature sensor. This temperature variability across the die is

highly dependent on the application being run. As a result, it is not possible to predict the

activation of the thermal control circuit by monitoring the on-die thermal diode.

System integrators should note that there is no defined correlation between the on-die thermal

diode and the processor case temperature. The temperature distribution across the die is affected

by the power being dissipated, type of activity the processor is performing (e.g., integer or

floating point intensive), and the leakage current. The dynamic and independent nature of these

effects makes it difficult to provide a meaningful correlation for the processor population.

System integrators that plan on using the thermal diode for system or component level fan control

to optimize acoustics need to refer to Acoustic Fan Control, Section 6.1.

4.2.7.1

Reading the On-Die Thermal Diode Interface

The on-die thermal diode is accessible from a pair of pins on the processor. The fan speed

controller remote thermal sense signals should be connected to these pins per the vendor’s

recommended layout guidelines.

Table 1. Thermal Diode Interface

Pin Name

Pin Number

Pin Description

THERMDA

AL1

Diode anode

THERMDC

AK1

Diode anode

Section	Page
Contents	3
Figures	6
Tables	7
Revision History	8
1 Introduction	9
1.1 Document Goals and Scope	9
1.1.1 Importance of Thermal Management	9
1.1.2 Document Goals	9
1.1.3 Document Scope	10
1.2 References	11
1.3 Definition of Terms	12
2 Processor Thermal/Mechanical Information	15
2.1 Mechanical Requirements	15
2.1.1 Processor Package	15
2.1.2 Heatsink Attach	17
2.1.2.1 General Guidelines	17
2.1.2.2 Heatsink Clip Load Requirement	17
2.1.2.3 Additional Guidelines	18
2.2 Thermal Requirements	18
2.2.1 Processor Case Temperature	18
2.2.2 Thermal Profile	19
2.2.3 TCONTROL	20
2.3 Heatsink Design Considerations	21
2.3.1 Heatsink Size	22
2.3.2 Heatsink Mass	22
2.3.3 Package IHS Flatness	22
2.3.4 Thermal Interface Material	23
2.4 System Thermal Solution Considerations	23
2.4.1 Chassis Thermal Design Capabilities	23
2.4.2 Improving Chassis Thermal Performance	23
2.4.3 Summary	24
2.5 System Integration Considerations	24
3 Thermal Metrology	25
3.1 Characterizing Cooling Performance Requirements	25
3.1.1 Example	26
3.2 Processor Thermal Solution Performance Assessment	27
3.3 Local Ambient Temperature Measurement Guidelines	27
3.4 Processor Case Temperature Measurement Guidelines	30
4 Thermal Management Logic and Thermal Monitor Feature	31
4.1 Processor Power Dissipation	31
4.2 Thermal Monitor Implementation	31
4.2.1 PROCHOT# Signal	32
4.2.2 Thermal Control Circuit	32
4.2.3 Operation and Configuration	33
4.2.4 On-Demand Mode	34
4.2.5 System Considerations	34
4.2.6 Operating System and Application Software Considerations	35
4.2.7 On-Die Thermal Diode	35
4.2.7.1 Reading the On-Die Thermal Diode Interface	35
4.2.7.2 Correction Factors for the On-Die Thermal Diode	36
4.2.8 THERMTRIP# Signal	37
4.2.8.1 Cooling System Failure Warning	37
5 Intel® Thermal/Mechanical Reference Design Information	39
5.1 Intel Validation Criteria for the Reference Design	39
5.1.1 Heatsink Performance Target	39
5.1.2 Acoustics	40
5.1.3 Altitude	40
5.1.4 Reference Heatsink Thermal Validation	41
5.1.5 Fan Performance for Active Heatsink Thermal Solution	41
5.2 Environmental Reliability Testing	42
5.2.1 Structural Reliability Testing	42
5.2.1.1 Random Vibration Test Procedure	42
5.2.1.2 Shock Test Procedure	42
5.2.2 Power Cycling	44
5.2.3 Recommended BIOS/Processor/Memory Test Procedures	44
5.3 Material and Recycling Requirements	44
5.4 Safety Requirements	45
5.5 Geometric Envelope for ATX Intel® Reference Thermal Mechanical Design	45
5.6 ATX Reference Thermal Mechanical Solution for the Intel® Pentium® 4 Processor in the 775–Land LGA Package	46
5.7 Reference Attach Mechanism	48
5.7.1 Structural Design Strategy	48
5.7.2 Mechanical Interface to the Reference Attach Mechanism	49
6 Acoustic Fan Speed Control	53
6.1 Acoustic Fan Speed Control	53
6.2 Thermal Solution Design	53
6.2.1 Compliance to Thermal Profile	53
6.2.2 Determine Thermistor Set Points	53
6.2.3 Minimum Fan Speed Set Point	54
6.3 Board and System Implementation	55
6.3.1 Choosing Fan Speed Control Settings	55
6.3.1.1 Temperature to begin Fan Acceleration	56
6.3.1.2 Minimum PWM Duty Cycle	58
6.4 Combining Thermistor and Thermal Diode Control	59

Intel 640 User Guide - Page 35

Operating System and Application Software, Considerations, On-Die Thermal Diode

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