Intel 640 User Guide - Page 28

Thermal Metrology

R

28

Thermal/Mechanical Design Guide

should be placed approximately 3 mm to 8 mm [0.1 to 0.3 in] above the fan hub vertically and

halfway between the fan hub and the fan housing horizontally as shown in Figure 5 (avoiding the

hub spokes). Using an open bench to characterize an active heatsink can be useful, and usually

ensures more uniform temperatures at the fan inlet. However, additional tests that include a solid

barrier above the test motherboard surface can help evaluate the potential impact of the chassis.

This barrier is typically clear Plexiglas*, extending at least 100 mm [4 in] in all directions beyond

the edge of the thermal solution. Typical distance from the motherboard to the barrier is 81 mm

[3.2 in]. For even more realistic airflow, the motherboard should be populated with significant

elements like memory cards, graphic card, and chipset heatsink. If a barrier is used, the

thermocouple can be taped directly to the barrier with a clear tape at the horizontal location as

previously described, half way between the fan hub and the fan housing. If a variable speed fan is

used, it may be useful to add a thermocouple taped to the barrier above the location of the

temperature sensor used by the fan to check its speed setting against air temperature. When

measuring T

A

in a chassis with a live motherboard, add-in cards, and other system components, it

is likely that the T

A

measurements will reveal a highly non-uniform temperature distribution

across the inlet fan section.

For

passive

heatsinks

, thermocouples should be placed approximately 13 mm to 25 mm

[0.5 to 1.0 in] away from processor and heatsink as shown in Figure 6. The thermocouples should

be placed approximately 51 mm [2.0 in] above the baseboard. This placement guideline is meant

to minimize the effect of localized hot spots from baseboard components.

Note:

Testing an active heatsink with a variable speed fan can be done in a thermal chamber to capture

the worst-case thermal environment scenarios. Otherwise, when doing a bench top test at room

temperature, the fan regulation prevents the heatsink from operating at its maximum capability.

To characterize the heatsink capability in the worst-case environment in these conditions, it is

then necessary to disable the fan regulation and power the fan directly, based on guidance from

the fan supplier.

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 28

Apassive Aheatsinks - graphics

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