Intel 640 User Guide - Page 12

Introduction

R

12

Thermal/Mechanical Design Guide

1.3

Definition of Terms

Term

Description

T

A

The measured ambient temperature locally surrounding the processor. The ambient

temperature should be measured just upstream of a passive heatsink or at the fan

inlet for an active heatsink.

T

C

The case temperature of the processor, measured at the geometric center of the

topside of the IHS.

T

E

The ambient air temperature external to a system chassis. This temperature is usually

measured at the chassis air inlets.

T

S

Heatsink temperature measured on the underside of the heatsink base, at a location

corresponding to

T

C

.

T

C-MAX

The maximum case temperature as specified in a component specification.

Ψ

CA

Case-to-ambient thermal characterization parameter (psi). A measure of thermal

solution performance using total package power. Defined as (T

C

– T

A

) / Total Package

Power.

Note: Heat source must be specified for

Ψ

measurements.

Ψ

CS

Case-to-sink thermal characterization parameter. A measure of thermal interface

material performance using total package power. Defined as (T

C

– T

S

) / Total Package

Power.

Note: Heat source must be specified for

Ψ

measurements.

Ψ

SA

Sink-to-ambient thermal characterization parameter. A measure of heatsink thermal

performance using total package power. Defined as (T

S

– T

A

) / Total Package Power.

Note:

Heat source must be specified for

Ψ

measurements.

TIM

Thermal Interface Material: The thermally conductive compound between the heatsink

and the processor case. This material fills the air gaps and voids, and enhances the

transfer of the heat from the processor case to the heatsink.

P

MAX

The maximum power dissipated by a semiconductor component.

TDP

Thermal Design Power: a power dissipation target based on worst-case applications.

Thermal solutions should be designed to dissipate the thermal design power.

IHS

Integrated Heat Spreader: A thermally conductive lid integrated into a processor

package to improve heat transfer to a thermal solution through heat spreading.

LGA775 Socket

The surface mount socket designed to accept the Pentium 4 processor in the 775–

land LGA package.

ACPI

Advanced Configuration and Power Interface.

Bypass

Bypass is the area between a passive heatsink and any object that can act to form a

duct. For this example, it can be expressed as a dimension away from the outside

dimension of the fins to the nearest surface.

Thermal Monitor

A feature on the Pentium 4 processor in the 775–land LGA package that attempts to

keep the processor die temperature within factory specifications.

TCC

Thermal Control Circuit: Thermal Monitor uses the TCC to reduce die temperature by

lowering effective processor frequency when the die temperature has exceeded its

operating limits.

T

DIODE

Temperature reported from the on-die thermal diode.

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 12

Definition of Terms

Page 12 highlights