Intel 640 User Guide - Page 53

Acoustic Fan Speed Control

R

Thermal/Mechanical Design Guide

53

6


6.1


As processor power has increased, the required thermal solutions have generated increasingly

more noise. Intel has added an option to the processor thermal specifications that allows the

system integrators to have a quieter system under typical usage. T

CONTROL

and the on-die thermal

diode provide the system integrator the means to implement a quieter system design.

Acoustic fan control implementations consist of the following items

•

A motherboard designed with a fan speed controller with the following functionality:

⎯

PWM fan control output

⎯

Remote thermal diode measurement capability

•

A motherboard with a 4-pin fan header for the processor heatsink fan.

•

Processor heatsink with 4–wire PWM controlled Fan.

A thermistor in the fan hub is recommended, but not a requirement. The reference solution

and the Boxed Pentium 4 Processor in 775–land LGA package have implemented a

thermistor into the design.

The following sections will discuss the necessary steps to implement Acoustic Fan Speed Control.

6.2

Thermal Solution Design

6.2.1

Compliance to Thermal Profile

The first step is to select or design a processor thermal solution that meets the thermal profile for

the Pentium 4 Processor in the 775–land LGA Package. See Section 2.2.2 for the definition of the

thermal profile then consult the processor datasheet.

The designer needs to ensure that when the heat sink fan is operating at full speed the thermal

solution will meet the T

C-MAX

limits at TDP. The slope of the thermal profile allows the designer

to make tradeoffs in thermal performance versus the inlet temperature to the processor fan

heatsink.

6.2.2

Determine Thermistor Set Points

A thermistor implemented in the hub of a fan is a first level of fan speed control. It provides an

easy and cost effective means to begin acoustic noise reduction. It will, by design, run the fan at

an appropriate speed based on the ambient conditions.

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 53

Acoustic Fan Speed Control

Page 53 highlights