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Thermal Metrology R ΨCS is strongly dependent on the thermal conductivity and thickness of the TIM between the heatsink and IHS. ΨSA is a measure of the thermal characterization parameter from the bottom of the heatsink to the local ambient air. ΨSA is dependent on the heatsink material, thermal conductivity, and geometry. It is also strongly dependent on the air velocity through the fins of the heatsink. Figure 4 illustrates the combination of the different thermal characterization parameters. Figure 4. Processor Thermal Characterization Parameter Relationships TA Heatsink TIM IHS Processor ΨCA TS TC LGA775 Socket 3.1.1 System Board Example The cooling performance, ΨCA, is then defined using the principle of thermal characterization parameter described above: • The case temperature TC-MAX and thermal design power TDP given in the processor datasheet. • Define a target local ambient temperature at the processor, TA. Since the processor thermal profile applies to all processor frequencies, it is important to identify the worst case (lowest ΨCA) for a targeted chassis characterized by TA to establish a design strategy such that a given heatsink can cover a given range of processor frequencies. The following provides an illustration of how one might determine the appropriate performance targets. The example power and temperature numbers used here are not related to any Intel processor thermal specifications, and are for illustrative purposes only. Assume the TDP, as listed in the processor datasheet, is 100 W and the maximum case temperature from the thermal profile for 100 W is 67 °C. Assume as well that the system airflow 26 Thermal/Mechanical Design Guide

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

Match case Limit results 1 per page

Thermal Metrology

Thermal/Mechanical Design Guide

is strongly dependent on the thermal conductivity and thickness of the TIM between the

heatsink and IHS.

is a measure of the thermal characterization parameter from the bottom of the heatsink to the

local ambient air.

is dependent on the heatsink material, thermal conductivity, and geometry.

It is also strongly dependent on the air velocity through the fins of the heatsink.

Figure 4 illustrates the combination of the different thermal characterization parameters.

Figure 4. Processor Thermal Characterization Parameter Relationships

TIM

LGA775 Socket

Processor

IHS

System Board

Heatsink

TIM

LGA775 Socket

Processor

IHS

System Board

Heatsink

3.1.1

Example

The cooling performance,

CA,

is then defined using the principle of thermal characterization

parameter described above:

•

The case temperature T

C-MAX

and thermal design power TDP given in the processor

datasheet

•

Define a target local ambient temperature at the processor, T

Since the processor thermal profile applies to all processor frequencies, it is important to identify

the worst case (lowest

) for a targeted chassis characterized by T

to establish a design

strategy such that a given heatsink can cover a given range of processor frequencies.

The following provides an illustration of how one might determine the appropriate performance

targets. The example power and temperature numbers used here are not related to any Intel

processor thermal specifications, and are for illustrative purposes only.

Assume the TDP, as listed in the processor datasheet, is 100 W and the maximum case

temperature from the thermal profile for 100 W is 67 °C. Assume as well that the system airflow