Intel 640 User Guide - Page 27

Thermal Metrology

R

Thermal/Mechanical Design Guide

27

has been designed such that the local ambient temperature is 38 °C. Then the following could be

calculated using Equation 1 from above:

Ψ

CA

= (T

C

– T

A

) / TDP = (67 – 38) / 100 = 0.29 °C/W

To determine the required heatsink performance, a heatsink solution provider would need to

determine

Ψ

CS

performance for the selected TIM and mechanical load configuration. If the

heatsink solution were designed to work with a TIM material performing at

Ψ

CS

≤

0.10 °C/W,

solving for Equation 2 from above, the performance of the heatsink would be:

Ψ

SA

=

Ψ

CA

−

Ψ

CS

= 0.29

−

0.10 = 0.19 °C/W

3.2

Processor Thermal Solution Performance

Assessment

Thermal performance of a heatsink should be assessed using a thermal test vehicle (TTV)

provided by Intel. The TTV is a stable heat source from which the user can take accurate power

measurements, whereas actual processors can introduce additional factors that can impact test

results. In particular, the power level from actual processors varies significantly due to variances

in the manufacturing process. The TTV provides consistent power and power density for thermal

solution characterization and results can be easily translated to real processor performance.

Once the thermal solution is designed and validated, it is strongly recommended to verify

functionality of the thermal solution on real processors and on fully integrated systems.

Contact your Intel field sales representative for further information on TTV or regarding accurate

measurement of the power dissipated by an actual processor.

3.3

Local Ambient Temperature Measurement

Guidelines

The local ambient temperature T

A

is the temperature of the ambient air surrounding the processor.

For a passive heatsink, T

A

is defined as the heatsink approaches air temperature; for an actively

cooled heatsink, it is the temperature of inlet air to the active cooling fan.

It is worthwhile to determine the local ambient temperature in the chassis around the processor to

understand the effect it may have on the case temperature.

T

A

is best measured by averaging temperature measurements at multiple locations in the heatsink

inlet airflow. This method helps reduce error and eliminate minor spatial variations in

temperature. The following guidelines are meant to enable accurate determination of the localized

air temperature around the processor during system thermal testing.

For

active heatsinks

, it is important to avoid taking measurement in the dead flow zone that

usually develops above the fan hub and hub spokes. Measurements should be taken at four

different locations uniformly placed at the center of the annulus formed by the fan hub and the fan

housing to evaluate the uniformity of the air temperature at the fan inlet. The thermocouples

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 27

Processor Thermal Solution Performance, Assessment, Local Ambient Temperature Measurement,

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