Intel 640 User Guide - Page 18

Processor Thermal/Mechanical Information

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18

Thermal/Mechanical Design Guide

2.1.2.3

Additional Guidelines

In addition to the general guidelines given above, the heatsink attach mechanism for the Pentium

4 processor in the 775–land LGA package should be designed to the following guidelines:

•

Holds the heatsink in place under mechanical shock and vibration events and applies force to

the heatsink base to maintain desired pressure on the thermal interface material

. Note that

the load applied by the heatsink attach mechanism must comply with the package

specifications described in the processor datasheet. One of the key design parameters is the

height of the top surface of the processor IHS above the motherboard. The IHS height from

the top of board is expected to vary from 7.517 mm to 8.167 mm. This data is provided for

information only, and should be derived from:

⎯

The height of the socket seating plane above the motherboard after reflow, given in the

LGA775 Socket Mechanical Design Guide

with its tolerances

⎯

The height of the package, from the package seating plane to the top of the IHS, and

accounting for its nominal variation and tolerances that are given in the corresponding

processor datasheet.

•

Engages easily, and if possible, without the use of special tools

. In general, the heatsink is

assumed to be installed after the motherboard has been installed into the chassis.

•

Minimizes contact with the motherboard surface during installation

and actuation to avoid

scratching the motherboard.

2.2

Thermal Requirements

Refer to the datasheet for the processor thermal specifications. The majority of processor power is

dissipated through the IHS. There are no additional components (e.g., BSRAMs) that generate

heat in this package. The amount of power that can be dissipated as heat through the processor

package substrate and into the socket is usually minimal.

Intel has introduced a new method for specifying the thermal limits for the Pentium 4 Processor in

the 775–land LGA package. The new parameters are the Thermal Profile and T

CONTROL

. The

Thermal Profile defines the maximum case temperature as a function of power being dissipated.

T

CONTROL

is a specification used in conjunction with the temperature reported by the on-die

thermal diode. Designing to these specifications allows optimization of thermal designs for

processor performance and acoustic noise reduction.

2.2.1

Processor Case Temperature

For the Pentium 4 processor in the 775–land LGA package, the case temperature is defined as the

temperature measured at the geometric center of the package on the surface of the IHS. For

illustration, Figure 2 shows the measurement location for a 37.5 mm x 37.5 mm

[1.474 in x 1.474 in] FCLGA4 package. Techniques for measuring the case temperature are

detailed in Section 3.4.

Note:

In case of conflict, the package dimensions in the processor datasheet supersedes dimensions

provided in this document.

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 18

Thermal Requirements

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