Intel 640 User Guide - Page 22

Processor Thermal/Mechanical Information

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Thermal/Mechanical Design Guide

2.3.1

Heatsink Size

The size of the heatsink is dictated by height restrictions for installation in a system and by the

amount of space available on the motherboard and other considerations for component height and

placement in the area potentially impacted by the processor heatsink. The height of the heatsink

must comply with the requirements and recommendations published for the motherboard form

factor of interest. Designing a heatsink to the recommendations may preclude using it in systems

adhering strictly to the form factor requirements, while still in compliance with the form factor

documentation.

For the ATX/microATX form factor, it is recommended to use:

•

The ATX motherboard keep-out footprint definition and height restrictions for enabling

components, defined for the platforms designed with the LGA775 socket in Appendix G of

this design guide.

•

The motherboard primary side height constraints defined in the

ATX Specification V2.1

and

the

microATX Motherboard Interface Specification V1.1

found at

http://www.formfactors.org/

.

The resulting space available above the motherboard is generally not entirely available for the

heatsink. The target height of the heatsink must take into account airflow considerations (for fan

performance for example) as well as other design considerations (air duct, etc.).

2.3.2

Heatsink Mass

With the need for pushing air cooling to better performance, heatsink solutions tend to grow

larger (increase in fin surface) resulting in increased mass. The insertion of highly thermally

conductive materials like copper to increase heatsink thermal conduction performance results in

even heavier solutions. As mentioned in Section 2.1, the heatsink mass must take into

consideration the package and socket load limits, the heatsink attach mechanical capabilities, and

the mechanical shock and vibration profile targets. Beyond a certain heatsink mass, the cost of

developing and implementing a heatsink attach mechanism that can ensure the system integrity

under the mechanical shock and vibration profile targets may become prohibitive.

The recommended maximum heatsink mass for the Pentium 4 processor in the 775–land LGA

package is

450g

. This mass includes the fan and the heatsink only. The attach mechanism (clip,

fasteners, etc.) is not included.

2.3.3

Package IHS Flatness

The package IHS flatness for the product is specified in the processor datasheet and can be used

as a baseline to predict heatsink performance during the design phase.

Intel recommends testing and validating heatsink performance in full mechanical enabling

configuration to capture any impact of IHS flatness change due to combined socket and heatsink

loading. While socket loading alone may increase the IHS warpage, the heatsink preload

redistributes the load on the package and improves the resulting IHS flatness in the enabled state.

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 22

Heatsink Size, Heatsink Mass, Package IHS Flatness

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