Intel 640 User Guide - Page 40

Intel® Thermal/Mechanical Reference Design Information

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40

Thermal/Mechanical Design Guide

5.1.2

Acoustics

To optimize acoustic emission by the fan heatsink assembly the reference design implements a

variable speed fan. A variable speed fan allows higher thermal performance at higher fan inlet

temperatures (T

A

) and lower thermal performance with improved acoustics at lower fan inlet

temperatures. The required fan speed necessary to meet thermal specifications can be controlled

by the fan inlet temperature and should comply with requirements below:

1.

Thermistor set points for fan speed in the reference thermal solution

•

High set point: T

A

= 38 °C;

Ψ

CA

= 0.29 °C/W

•

Low set point: T

A

= 30 °C;

Ψ

CA

= 0.37 °C/W

The example above uses settings for the Pentium 4 processor 5xx sequence, but would be

similar for the Pentium 4 processor 6xx sequence or Pentium 4 processor Extreme Edition.

2.

Fan heatsink assembly acoustic performance:

•

Acoustic performance is defined in terms of declared sound power (LwAd) as defined in ISO

9296 standard, and measured according to ISO 7779.

•

LwAd should not exceed 5.7 BA at the high set point temperature.

•

LwAd should not exceed 4.5 BA at the low set point temperature.

While the fan hub thermistor helps optimize acoustics at high processor workloads by adapting

the maximum fan speed to support the processor thermal profile, additional acoustic

improvements can be achieved at lower processor workload by using the T

CONTROL

specifications

described in Section 2.2.3. Intel’s recommendation is to use the

Fan Specification for 4 Wire

PWM Controlled Fans

to implement fan speed control capability based on-die thermal diode

temperature. Refer to Chapter 6 for further details.

Note:

Heatsinks providing omni-directional airflow may have to provide cooling to other components

on the board, like voltage regulator and MCH. This may impact the lowest speed at which the fan

may run, and thus impact fan low set point, usually raising the minimum fan speed based on

processor thermal specification compliance only. In any case, complying with processor thermal

profile must be met at all time.

5.1.3

Altitude

The reference heatsink solution was evaluated at sea level. However, many companies design

products that must function reliably at high altitude, typically 1,500 m [5,000 ft] or more. Air-

cooled temperature calculations and measurements at sea level must be adjusted to take into

account altitude effects like variation in air density and overall heat capacity. This often leads to

some degradation in thermal solution performance compared to what is obtained at sea level, with

lower fan performance and higher surface temperatures. The system designer needs to account for

altitude effects in the overall system thermal design to make sure that the T

C

requirement for the

processor is met at the targeted altitude.

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 40

Acoustics, Altitude

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