Thermal Management for the Boxed Intel® Celeron® Processor

Introduction

Systems using Intel® Celeron® 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® Celeron® processors" refers to processors packaged for use by system integrators.)

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

The Celeron processor uses the Thermal Monitor feature (see Celeron 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 Celeron 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 Celeron 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 Celeron processor-based systems remain below the lower set point of 38C for nominal operating environments, as shown in Table 1.

In addition to the Thermal Monitor feature, the boxed Intel Celeron 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 and processor power consumption levels.

The 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. Thus, it is was designed in such a way that it would cool the processor when running under stressfull application loads at any given ambient temperature (up to 38C). See figure1 for a graphical represntation of the typical fan speed opertion under given internal chassis temperatures.

Point Z in figure 1 represents the upper set point or worse case ambient temperature of 38C. Point X represents the lower set point or the slowest possible fan speed at an ambient temperature of 30C. (Also see Table 1)

The internal chassis temperature is required to be maintained at 38°C (or lower).

Table 1. Boxed Processor Variable Fan Heatsink Set Points

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 Celeron processor, it is imperative to carefully consider the thermal management of the system and verify the system design with 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 Celeron 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 Celeron processor must be securely attached to the processor. Thermal interface material (preapplied 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.) Be sure to follow the installation procedures documented in the Integration Overview For the boxed Intel® Celeron processor .

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

Chassis Recommendations

Systems based on the Intel® Celeron® Processor must use a chassis that comply with the ATX specification (revision 2.2 or later) or microATX specification (revision 1.0 or later), depending on the motherboard form factor. Intel recommends system integrators using ATX form factor motherboards to choose a chassis that complies with the ATX specification (revision 2.2 or later). Likewise, system integrators using microATX form factor motherboards should choose a chassis that complies with the microATX specification (1.0 or later).

The chassis must also support a lower internal ambient temperature than many standard ATX and microATX desktop chassis. The internal chassis temperature for systems based on Celeronprocessors should not exceed 38°C when the chassis is used in a maximum expected room temperature of 35°C. Most chassis designed for the Celeron processor use extra internal chassis fans to improve airflow and many include ducting to bring cool air directly to the processor fan heatsink. A 38°C internal chassis temperature is best acieved by using a Thermally Advantaged Chassis (TAC) version 1.1.

It is recommended to use a Thermally Advantaged Chassis on the Tested Chassis List to ensure proper chassis airflow, electrical support (ATX12V or SFX12V power supply), and compatibility with boxed Intel Celeron processors. Chassis that pass this thermal testing provide system integrators with a starting place for determining which chassis to evaluate. It is strongly recommended that system integrators perform thermal testing on the chassis selected for each configuration of Celeron processor-based systems, even when using a chassis on the tested chassis list.

Intel® Celeron® Processor Thermal Specifications

The Intel® Celeron® processor datasheet (also listed in Table 2 ) lists the power dissipation of Intel Celeron processors at various processor numbers. System integrators can perform thermal testing using thermocouples to determine the temperature of the processor's integrated heat spreader (see Intel® Celeron® Duo processor 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 Core2 Duo 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 the Intel Celeron processor should have a maximum expected temperature of 38°C in the maximum expected external ambient (which is typically 35°C). This is best achieved by using a Thermally Advantaged Chassis.

Table 2. Boxed Intel® Celeron® Processor Thermal Specifications

Notes:

1. These specifications are from theIntel® Celeron® Processor Datasheet