Intel 640 User Guide - Page 59

Acoustic Fan Speed Control

R

Thermal/Mechanical Design Guide

59

6.4

Combining Thermistor and Thermal Diode Control

There is no closed loop control between the FSC and the thermistor, but they work in tandem to

provide the maximum fan speed reduction. As discussed in Section 6.2.2, the thermistor

establishes the VSF curve. This curve will determine the maximum fan speed as a function of the

ambient temperature and by design provides a

Ψ

CA

sufficient to meet the thermal profile. The

FSC, by measuring the processor on-die thermal diode will command the fan to reduce speed

below the VSF curve in response to processor workload. Conversely if the processor workload

increases the FSC will command the fan via the PWM duty cycle to accelerate the fan up to the

limit imposed by the VSF curve.

Figure 21. Diode and Thermistor

Fan Speed

(RPM)

Inlet Temperature (°C)

Full

Speed

30

38

Min.

Operating

Variable Speed Fan

(VSF) Curve

Fan Speed

Operating Range

with FSC

34

Min %

Fan Speed

(% PWM Duty Cycle)

100 %

Fan Speed

(RPM)

Inlet Temperature (°C)

Full

Speed

30

38

Min.

Operating

Variable Speed Fan

(VSF) Curve

Fan Speed

Operating Range

with FSC

34

Min %

Fan Speed

(% PWM Duty Cycle)

100 %

6.5

Interaction of Thermal Profile and T

CONTROL

The Pentium 4 processor in the 775–land LGA packaged thermal specification is comprised of the

two parameters, T

CONTROL

and the maximum case temperature defined by the Thermal Profile.

The minimum requirement for thermal compliance is to ensure the thermal solution, by design,

meets the thermal profile.

If the system design will incorporate variable speed fan control, Intel requires monitoring the on-

die thermal diode to implement acoustic fan speed control. The value of the on-die thermal diode

temperature determines which specification must be met.

•

On-die Thermal Diode less than T

CONTROL

⎯

When the thermal solution can maintain the thermal diode temperature to less than

T

CONTROL

then the fan speed can be reduced.

•

On-die Thermal Diode equal to T

CONTROL

⎯

The PWM duty cycle must be = 100%

•

On-die Thermal Diode greater than T

CONTROL

⎯

The T

C

must be maintained at or below the Thermal Profile for the measured power

dissipation.

§

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 59

Combining Thermistor and Thermal Diode Control, Interaction of Thermal Profile and T

Page 59 highlights