Updated December 2005

• Introduction
• Thermal Management
• Installing the Heatsink
• Chassis Recommendations
• Managing System Airflow
• Performing Thermal Testing
• Intel® Xeon® Processor Thermal Specifications

Introduction

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

Thermal management in boxed Intel Xeon processor-based systems can affect both the performance and noise level of the system. The Intel Xeon processor uses either the Thermal Monitor 1 or Thermal Monitor 2 feature, depending on the BIOS setting, to protect the processor during times where the silicon would otherwise operate above specification. In a properly designed system, this feature should never become active. This feature is intended to provide protection for unusual circumstances like higher than normal ambient air temperatures or failure of a system thermal management component (such as a system fan). While the Thermal Monitor 1/2 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 ambient temperatures to prevent the Intel Xeon processor from entering a Thermal Monitor 1/2 active state. Information on the Thermal Monitor 1/2 feature can be found in the Intel Xeon Processor Datasheet.

Additionally, the boxed Intel Xeon processor heatsink may make use of either an active or passive thermal solution. For the active thermal solution, the fan operates at a speed dictated by the fan speed control which relates to the CPU temperature. In systems using passive thermal solutions, ducting is required conforming to the requirements specified in the processor datasheet. When using the passive thermal solution with chassis ducting, adequate airflow will be generated across the processor heatsink as long as the ambient temperature is maintained below the maximum specification. Please refer to the Intel Xeon Processor Datasheet for more information on this topic.

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 Xeon 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 Xeon processor. System integrators using the boxed Intel Xeon processor should become familiar with this document.

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. It is the responsibility of the system integrator to select a server chassis that ensures adequate system airflow.

Installing the Heatsink
The heatsink included with the boxed Intel Xeon processor must be securely attached to the processor. Thermal interface material (pre-applied to the thermal solution) provides effective heat transfer from the processor to the fan heatsink.

Chassis Recommendations
System integrators must use an SSI chassis that has been specifically designed to support the boxed Intel Xeon processor. Chassis specifically designed to support the Intel Xeon processor will ship with proper mechanical and electrical support for the processor in addition to having improved thermal performance. Intel has tested chassis for use with boxed Intel Xeon processors using enabled third party boards. The chassis that pass this thermal testing provide system integrators with a starting place for determining which chassis to evaluate.

Managing System Airflow
The following are factors which determine system airflow:

• Chassis Design
• Chassis Size
• Location of Chassis Air Intake and Exhaust Vents
• Power Supply Fan Capacity and Venting
• Location of the Processor Slot(s)
• Placement of Add-in Cards and Cables

System integrators must ensure adequate airflow through the system to allow the heatsink to work effectively. Proper attention to airflow when selecting subassemblies and building systems is important for good thermal management and reliable system operation.

Integrators use three basic motherboard-chassis-power supply form factors for servers and workstations: SSI*, ATX variations and the older Server AT form factor. Due to cooling and voltage considerations, Intel recommends the use of SSI form factor motherboards and chassis for the boxed Intel Xeon processor.

Server AT form factor motherboards are not recommended because such designs are not standardized for effective thermal management. However, some chassis designed exclusively for Server AT form factor motherboards may yield efficient cooling.

The following is a list of guidelines to be used when integrating a system:

• Chassis vents must be functional and not excessive in quantity: Integrators should be careful not to select chassis that contain cosmetic vents only. Cosmetic vents are designed to look as if they allow air flow but little or no air flow actually exists. Chassis with excessive air vents should also be avoided. In this case, very little air flows over the processor and other components. In SSI chassis, I/O shields must be present. Otherwise, the I/O opening may provide for excessive venting.
• Vents must be properly located: Systems must have properly located intake and exhaust vents. The best locations for air intakes allow air to enter the chassis and directly flow over the processor. Exhaust vents should be situated so that air flows on a path through the system, over various components, before exiting. The specific location of vents depends upon the chassis. For SSI systems, exhaust vents should be located both in the bottom front and bottom rear of the chassis. Also, for SSI systems, I/O shields must be present to allow the chassis to vent air as designed. Lack of an I/O shield may disrupt proper airflow or circulation within the chassis.
• Power Supply Airflow Direction: It is important to choose a power supply that has a fan that exhausts air in the proper direction. Some power supplies have markings noting airflow direction.
• Power Supply Fan Strength: PC power supplies contain a fan. For some chassis where the processor is running too warm, changing to a power supply with a stronger fan can greatly improve airflow.
• Power Supply Venting: A lot of air flows through the power supply unit, which can be a significant restriction if not well vented. Choose a power supply unit with large vents. Wire finger guards for the power supply fan offer much less airflow resistance than openings stamped into the sheet metal casing of the power supply unit.
• System Fan - Should It Be Used? Some chassis may contain a system fan (in addition to the power supply fan) to facilitate airflow. A system fan is typically used with passive heatsinks. In some situations, a system fan improves system cooling. Thermal testing both with a system fan and without the fan will reveal which configuration is best for a specific chassis.
• System Fan Airflow Direction: When using a system fan, ensure that it draws air in the same direction as the overall system airflow. For example, a system fan in a SSI system should act as an exhaust fan, pulling air from within the system out through the rear or front chassis vents.
• Protect Against Hot Spots: A system may have a strong airflow, but still contain "hot spots." Hot spots are areas within the chassis that are significantly warmer than the rest of the chassis air. Improper positioning of the exhaust fan, adapter cards, cables, or chassis brackets and subassemblies blocking the airflow within the system, can create such areas. To avoid hot spots, place exhaust fans as needed, reposition full-length adapter cards or use half-length cards, re-route and tie cables, and ensure space is provided around and over the processor.

Performing Thermal Testing

Differences in motherboards, power supplies, add-in peripherals and chassis all affect the operating temperature of systems and the processors that run them. Thermal testing is highly recommended when choosing a new supplier for motherboards or chassis, or when starting to use new products. Thermal testing can determine if a specific chassis-power supply-motherboard configuration provides adequate airflow for boxed Intel Xeon processors. To begin determining the best thermal solution for your Intel Xeon processor based systems, contact your motherboard vendor for chassis and fan configuration recommendations.