Introduction

Systems using Intel® Pentium® 4 processors all require thermal management. This document assumes a general knowledge of and experience with system operation, integration, and thermal management. Integrators who follow the recommendations presented can provide their customers with more reliable systems and will see fewer customers returning with thermal management issues. (The term "boxed Intel® Pentium® 4 processors" refers to processors packaged for use by system integrators.)

Thermal management in boxed Intel® Pentium® 4 processor-based systems can affect both the performance (Thermal Monitor feature) and noise level (variable speed fan) of the system.

The Pentium® 4 processor uses the Thermal Monitor feature (see Pentium® 4 Processor Datasheet for details) to protect the processor during times where the silicon would otherwise operate above specification. The feature is intended to help prevent long-term reliability damage to the processor and provide protection for unusual circumstances like higher than normal internal chassis temperatures (and inlet air temperature, defined as the air temperature entering the processor fan heatsink) or failure of a system thermal management component (such as a system fan). In its active state, the Thermal Monitor feature scales back processor power consumption, if the factory programmed thermal design temperature is exceeded (see Table 2 or the Pentium® 4 Processor Datasheet for complete thermal specifications.). While the Thermal Monitor feature is active, the system's performance may drop below its normal peak performance level. It is critical that systems be designed to maintain low enough internal chassis and processor inlet air temperatures to prevent the Pentium® 4 processor from entering a Thermal Monitor active state. In a properly thermal managed and designed system, the Thermal Monitor feature should never become active. It is recommended that the internal chassis temperature for boxed Intel® Pentium® 4 processor-based systems remain below the lower set point for nominal operating environments, as shown in Table 1 and Figure 1 .

In addition to the Thermal Monitor feature, the boxed Intel® Pentium® 4 processor fan heatsink uses a high quality variable speed fan which allows the processor to remain within its operating thermal specifications by running at different speeds over a short range of internal chassis temperatures. The processor fan operates at a low speed while internal chassis temperatures are low. If internal chassis temperatures increase beyond a lower set point, the fan speed will rise linearly with the internal chassis temperature until the higher set point is reached. As fan speed increases, so does the noise that the fan generates. Systems should be designed to provide air around the boxed processor fan heatsink that remains below the lower set point. These set points, represented in Table 1 and Figure 1 can vary by a few degrees from fan heatsink to fan heatsink.

Table 1.Boxed Processor Fan Heatsink Set Points

¹Set point variance is approximately ±1°C from fan heatsink to fan heatsink.

Figure 1. Internal Chassis Temperature Impact On Noise

 


Allowing processors to operate at temperatures beyond their maximum specified operating temperature may shorten the life of the processor and can cause unreliable operation. Meeting the processor's temperature specification is ultimately the responsibility of the system integrator. When building quality systems using the boxed Intel® Pentium® 4 processor, it is imperative to carefully consider the thermal management of the system and verify the system design with thermal testing. This document details specific thermal requirements of the boxed Intel Pentium® 4 processor. System integrators using the boxed Intel® Pentium® 4 processor should become familiar with this document as well as the two related documents listed below.

Related Documents

1. System Thermal Management for Boxed Intel Processor-Based Desktop PCs
   
   This document details general recommendations for improving system thermal management in desktop systems that use boxed Intel processors.
2. Thermal Testing with Thermocouples and Thermal Meters on Intel Boxed Processor-Based Desktop PCs
   
   This document describes the use of thermocouples and thermal meters for testing Intel boxed processor-based desktop systems. Thermocouples can be used to test temperatures critical to the proper operation of boxed processors. The document also discusses what software to use when performing thermal testing.

Thermal Management

Proper "thermal management" depends on two major elements: a heatsink properly mounted to the processor, and effective airflow through the system chassis. The ultimate goal of thermal management is to keep the processor at or below its maximum operating temperature.

Proper thermal management is achieved when heat is transferred from the processor to the system air, which is then vented out of the system. Boxed Intel® Pentium® 4 processors are shipped with a high-quality variable speed fan heatsink, which can effectively transfer processor heat to the system air. It is the responsibility of the system integrator to ensure adequate system airflow.

Fan Heatsink

The fan heatsink included with the boxed Intel® Pentium® 4 processor must be securely attached to the processor. Thermal interface material (either attached to the bottom of the heatsink or applied during system integration with an applicator) provides effective heat transfer from the processor to the fan heatsink. The fan cable provides power to the fan by connecting to a motherboard-mounted power header and also allows the fan to provide fan speed information to the motherboard. (Only motherboards with hardware monitoring circuitry can use the fan speed signal.) Be sure to follow the installation procedures documented in the boxed processor manual and the Integration Overview (for the boxed Intel® Pentium® 4 processor in the 423-pin package or the boxed Intel® Pentium® 4 processor in the 478-pin package ).

The fan is a high-quality ball bearing fan that provides a good local air stream. This air stream transfers heat from the heatsink to the air inside the system. However, moving heat to the system air is only half the task. Sufficient system airflow is also needed in order to exhaust the air. Without a steady stream of air through the system, the fan heatsink will re-circulate warm air, and therefore may not cool the processor adequately.

Thermal Interface Material Replacement for Fan Heatsink

• Thermal Interface Material Attached to the Heatsink
  
  Intel does not recommend the removal of the thermal interface material located on the bottom of the boxed processor fan heatsink. Removal of this material may cause damage to the processor and will void the boxed processor warranty. If you must remove and re-use the fan heatsink, it will require replacement. Also, if the thermal interface material is at all damaged, you must also replace the fan heatsink. Contact Intel Customer Support to receive a replacement fan heatsink.
  
  
• Thermal Interface Material in an Applicator
  
  Using the boxed processor without properly applying the included thermal interface material may cause damage to the processor and will void the boxed processor warranty. If you must remove and re-use the fan heatsink, a new application of thermal interface material is required. Contact Intel Customer Support to receive additional thermal interface material in an applicator.

Chassis Recommendations

Intel® Pentium® 4 Processor Thermal Specifications