Intel 640 User Guide - Page 25

Thermal Metrology

R

Thermal/Mechanical Design Guide

25

3

Thermal Metrology

This chapter discusses guidelines for testing thermal solutions, including measuring processor

temperatures. In all cases, the thermal engineer must measure power dissipation and temperature

to validate a thermal solution. To define the performance of a thermal solution the “thermal

characterization parameter”,

Ψ

(“psi”) will be used.

3.1

Characterizing Cooling Performance Requirements

The idea of a “thermal characterization parameter”,

Ψ

(“psi”), is a convenient way to characterize

the performance needed for the thermal solution and to compare thermal solutions in identical

situations (same heat source and local ambient conditions). The thermal characterization

parameter is calculated using total package power.

Note:

Heat transfer is a three-dimensional phenomenon that can rarely be accurately and easily modeled

by a single resistance parameter like

Ψ

.

The case-to-local ambient thermal characterization parameter value (

Ψ

CA

) is used as a measure of

the thermal performance of the overall thermal solution that is attached to the processor package.

It is defined by the following equation, and measured in units of °C/W:

Ψ

CA

= (T

C

- T

A

) / P

D

(Equation

1)

Where:

Ψ

CA

=

Case-to-local ambient thermal characterization parameter (°C/W)

T

C

=

Processor case temperature (°C)

T

A

=

Local ambient temperature in chassis at processor (°C)

P

D

=

Processor total power dissipation (W) (assumes all power dissipates through the

IHS)

The case-to-local ambient thermal characterization parameter of the processor,

Ψ

CA

, is comprised

of

Ψ

CS

, the thermal interface material thermal characterization parameter, and of

Ψ

SA

, the sink-to-

local ambient thermal characterization parameter:

Ψ

CA

=

Ψ

CS

+

Ψ

SA

(Equation 2)

Where:

Ψ

CS

= Thermal characterization parameter of the thermal interface material (°C/W)

Ψ

SA

= Thermal characterization parameter from heatsink-to-local ambient (°C/W)

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 25

Thermal Metrology

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