Processors
Intel® Pentium® 4 Processors
Thermal Management for boxed LGA775-based Intel® Pentium® 4 Processors


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 Intel® Pentium® 4 Processor uses the Thermal Monitor feature 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) 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 Intel® 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 (38C) for nominal operating environments, as shown in Table 1.

In addition to the Thermal Monitor feature, the Boxed Intel® Pentium® 4 Processor fan heatsink uses a newly designed, 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 and processor power consumption levels.

As processor power has increased, required thermal solutions have generated more noise. Intel has added an option to the boxed processor that allows system integrators to have a quieter system in the most common usage.

Previous generation boxed Intel fan heatsinks contain built in circuitry to control fan speed. They have a thermistor in the fan hub which measures the chassis ambient air temperature. The fan circuitry then adjusts the fan speed to properly cool the processor at the slowest speed allowable. If the chassis ambient temperature is cool then the processor will run slower and quieter. If the ambient temperature is hot, then the fan will run faster.

This fan was designed to work in a variety of operating conditions so it had to be designed in such a way that it would cool the processor when running at its maximum power at any given ambient temperature (up to 38C). In normal operating environments the processor is running at its maximum power only a fraction of the time.

Under most conditions the fan is spinning faster and louder than necessary. (The fan heatsink is required to work this way so that it will properly cool the CPU in all specified operating environments.)

Intel has been aware of customer concerns over increasing fan noise. Intel has now designed a new fan speed control technology to take advantage of the fact that the processor is not always running at its maximum power. This was done by basing the fan speed control on actual CPU temperature and power usage.

The speed of the new fan heatsink is controlled by the additional 4th wire of the fan cable. (The new technology is sometimes referred to as “4-wire fan speed control.”)

The additional 4th wire sends a signal from the motherboard to the fan heatsink to control its speed. There is a thermal diode in the processor which measures actual CPU temperature. The processor sends information to the motherboard about its specific thermal requirements and the actual processor temperature. The motherboard then uses this information to optimally control the speed of the processor fan.

Figure 1 shows the current fan speed curve (Red) of a 3-wire, fan heatsink-thermistor based fan speed control. The additional curves in blue represent fan operations at lower CPU temperature and power consumption levels based on the 4-wire fan speed control fan heatsink.

The, “Max Temp,” in figure 1 represents the upper set point or worse case ambient temperature of 38C. The, Min Temp,” represents the lower set point or the slowest possible fan speed at an ambient temperature of 30C. (Also see Table 1)

The acoustic benefits of the 4-wire based fan speed control may vary depending on the specific motherboard implementation. (The acoustic benefits are reliant on the motherboard design.)

If the new 4-pin active fan heat sink solution is connected to an older 3-pin motherboard
CPU fan header it will default back to a fan heatsink thermistor controlled mode, allowing compatibility with existing 3-pin motherboard designs. The fan heatsink has onboard circuitry that will control the fan speed based on internal chassis ambient temperature.

A 4-wire fan does not guarantee a quieter system. If the processor is being used in a hot environment and under heavy loads the fan will have to run fast enough to properly cool the processor. The internal chassis temperature is required to be maintained at 38°C (or lower). See the Integration Overview for Systems Based on the Boxed Intel® Pentium® 4 Processor in the LGA775 Package.

Table 1. Boxed Processor Variable Fan Heatsink Set Points

For Boxed Intel® Pentium® 4 Processors in the 775-land package
Internal Chassis Temperature (°C) Boxed Processor Fan Heatsink Set Points
X <= 301 Lower Set Point: Fan speed constant at lowest fan speed. Recommended temperature for nominal operating environment.
Y = 34 Recommended maximum internal chassis temperature for boxed Intel Pentium 4 Processor-based systems.
Z >= 381 Higher Set Point: Fan speed constant at highest fan speed.
1 Set 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.

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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.

Do not, under any circumstances, place a sticker or any other material on top of the processor Integrated Heat Spreader (IHS). Only Thermal Interface Material (TIM) should be used between the processor IHS and the heatsink. Using any other material will degrade the thermal transfer characteristics and could potentially damage the processor (causing the warranty to be voided).

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Fan heat sink

The fan heatsink included with the Boxed Intel® Pentium® 4 Processor must be securely attached to the processor. Thermal interface material (pre-applied, attached to the bottom of the heatsink) 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 transfer of information to and from the fan with the motherboard. (Only motherboards with hardware monitoring circuitry can use the fan speed signal. Additional circuitry is required for motherboard based fan speed control) Be sure to follow the installation procedures documented in the boxed processor manual.

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 recirculate warm air, and therefore may not cool the processor adequately.

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Thermal interface material replacement for fan heatsink

Thermal interface material is required for proper heat transfer from the processor to the fan heatsink. The boxed Intel Pentium 4 Processor will have thermal interface material attached to the bottom of the 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 reuse 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.

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Chassis recommendations

Intel recommends system integrators using ATX form factor motherboards to choose a chassis that complies with the ATX 2.01 (or later) specification. System integrators using microATX form factor motherboards should choose a chassis that complies with the microATX 1.0 (or later) specification.

A properly cooled system can help the processor run more reliably and minimize the acoustic noise levels generated from running the cooling fan at higher speeds. .

It is recommended to use a chassis that features good airflow to ensure proper chassis airflow, electrical support (ATX12V or SFX12V power supply), and compatibility with boxed Intel Pentium 4 Processors using an Intel® Desktop Board. Chassis that pass this thermal testing provide system integrators with a starting place for determining which chassis to evaluate.

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Intel® Pentium® 4 Processor thermal specifications

The Intel® Pentium® 4 Processor datasheet (also listed in Table 2 ) lists the power dissipation of Intel® Pentium® 4 Processors at various processor numbers. For Intel® Pentium® 4 Processors in the 775-land package, processors with different Platform Compatibility Guides have dissipated different amounts of heat. Typically, the highest speed processor in a given Platform Compatibility Guide will dissipate the most power. (The highest speed processor will be closest to the maximum specification.) When building systems that will feature many operating frequencies, testing should be performed using the highest frequency processor supported at the highest Platform Compatibility Guide supported, because it dissipates the most power. System integrators can perform thermal testing using thermocouples to determine the temperature of the processor's integrated heat spreader (see Intel® Pentium® processor in the 775-land Package Thermal Design Guidelines, for details) or the temperature of the air entering the boxed processor fan heatsink inlet.

A simple evaluation of the temperature of the air entering the fan heatsink can provide confidence in the system's thermal management. For Boxed Intel® Pentium® 4 Processors, the testing point is at the center of the fan hub, approximately 0.3 inches above the fan. Evaluation of test data makes it possible to determine if a system has sufficient thermal management for the boxed processor. Systems based on Intel Pentium 4 Processors in the 775-land package should have a maximum expected temperature of 38°C in the maximum expected external ambient (which is typically 35°C).

Table 2. Boxed Intel Pentium 4 Processor Thermal Specifications

Processor Number Processor Core Frequency(GHz) Platform Compatibility Guide Processor Package Maximum Case Temperature (°C) Maximum Recommended Fan Inlet Temperature (°C) Processor Thermal Design Power (W) Notes
661 3.60 05A 775-land (FC-LGA4) 69.2 38 86 1,8
651 3.40 05A 775-land (FC-LGA4) 69.2 38 86 1,8
641 3.20 05A 775-land (FC-LGA4) 69.2 38 86 1,8
631 3.00 05A 775-land (FC-LGA4) 69.2 38 86 1,8
N/A 3.73 04B 775-land (FC-LGA4) 70.8 38 115 2,7
660 3.60 04B 775-land (FC-LGA4) 70.8 38 115 2,7
650 3.40 04A 775-land (FC-LGA4) 66.6 38 84 2,7
640 3.20 04A 775-land (FC-LGA4) 66.6 38 84 2,7
630 3.00 04A 775-land (FC-LGA4) 66.6 38 84 2,7
N/A 3.46 N/A 775-land (FC-LGA4) 66 38 110.7 2,4
560J 3.60 04B 775-land (FC-LGA4) 70.8 38 115 1,6
560 3.60 04B 775-land (FC-LGA4) 70.8 38 115 1
N/A 3.60 04B 775-land (FC-LGA4) 70.8 38 115 1,5
550J 3.40 04A 775-land (FC-LGA4) 66.6 38 84 1,6
N/A 3.40 N/A 775-land (FC-LGA4) 66 38 109.6 2,4
550 3.40 04B 775-land (FC-LGA4) 70.8 38 115 1
N/A 3.40 04B 775-land (FC-LGA4) 70.8 38 115 1,5
540J 3.20 04A 775-land (FC-LGA4) 66.6 38 84 1,6
540 3.20 04A 775-land (FC-LGA4) 66.6 38 84 1
N/A 3.20 04A 775-land (FC-LGA4) 66.6 38 84 1,5
530 3.0 04A 775-land (FC-LGA4) 66.6 38 84 1
520J 2.80 04A 775-land (FC-LGA4) 66.6 38 84 1,6
520 2.80 04A 775-land (FC-LGA4) 66.6 38 84 1
Note
  1. These specifications are from the Intel® Pentium® 4 Processor in the 775-land Package Datasheet
  2. These specifications are from the Intel® Pentium® 4 Processor Extreme Edition in the 775-land Package Datasheet
  3. The maximum case temperature is defined over a range depending on current processor power consumption. See "Thermal Specifications and Design Considerations," section of the Intel® Pentium® 4 Processor in the 775-land Package Datasheet
  4. This is a Boxed Intel® Pentium® 4 Processor with HT Technology Extreme Edition processor
  5. This processor supports Intel® 64 Architecture
  6. This is an E step processor
  7. This processor is based on Intel 90 nanometer process technology
  8. This processor is based on Intel 65 nanometer process technology

This applies to:

Intel® Pentium® 4 Processors



Solution ID: CS-031422
Last Modified: 23-Jan-2014
Date Created: 22-Feb-2010
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