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4.
Thermal Specifications
For the purposes of this design guideline, the following assumptions have been made about the
requirements for proper operation and reliability of the processor:
Considering the power dissipation levels and typical system ambient environments (T
processor's temperature cannot be maintained at or below the specified guidelines without additional
thermal enhancement to dissipate the heat generated by the processor.
The thermal characterization data described in later sections illustrates that both a thermal-cooling
device and reasonable system airflow are needed. The size and type (passive or active) of thermal
cooling device and the amount of system airflow are related and can be traded against each other to
meet specific system design constraints. In typical systems, board layout, spacing, and component
placement limit the thermal solution size. Airflow is determined by the size and number of fans,
along with their placement in relation to the components and the airflow channels within the system.
In addition, acoustic noise constraints may limit the size, number, and types of fans that can be used
in a particular design.
To develop a reliable, cost-effective thermal solution, all of the above variables must be considered.
Thermal characterization and simulation should be carried out at the entire system level accounting for
the thermal requirements of each component.
4.1.
Processor Case Temperature
The Integrated Heat Spreader (IHS) is intended to provide the common interface and attach location for
all thermal solutions for FC-PGA2 packaged processors. The IHS acts to spread the heat from the small
area of the processor die to the larger surface area of the IHS, allowing more efficient heat transfer using
heatsink thermal solutions. These solutions can be active or passive. Active solutions are those where a
fan is directly attached to the heatsink. A passive heatsink uses system airflow forced in some manner to
pass-through the heatsink fins. Considerations in heatsink design include:
Local-ambient temperature at the heatsink (T
Surface area of the heatsink
Property of materials (including thermal resistance or conductivity)
Volume and velocity of airflow over the heatsink surface area
Power being dissipated by the processor and its associated power density
Physical volumetric constraints placed by the system
Techniques for measuring case temperatures are provided in Section 7: Thermal Metrology.
249660-001
®
®
Intel
Pentium
III Processor in the FC-PGA2 Package Thermal Design Guidelines
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