Intel Pentium 4 Processor in the 478-Pin Package Thermal Design Guidelines

Intel

Pentium

4 Processor in the 478-Pin Package Thermal Design Guidelines

Design Guide 51

4 Conclusion

As the complexities of today’s microprocessors increase, the power dissipation requirements

become more exacting. Care must be taken to ensure that the additional power is properly

dissipated. Heat can be dissipated using passive heatsinks, fans and/or active cooling devices.

Incorporating ducted airflow solutions into the system thermal design can yield additional margin.

The Intel

Pentium

4 processor in the 478-pin package and the Intel

Pentium

4 processor with

512 KB L2 cache on .13 micron process have thermal management logic integrated into the

processor silicon. Their circuits may be configured to automatically control the processor

temperature through the use of the Thermal Monitor feature. In the event it reaches a factory-

calibrated temperature, the processor periodically stops the internal clocks in order to reduce

power consumption and allow the processor to cool down and stay within thermal specifications.

Various registers and bus signals are available to monitor and control the processor thermal status.

A chassis cooling solution designed to the thermal design power (TDP) as specified in the

processor datasheet document can adequately cool the processor to a level where activation of the

Thermal Monitor feature is either very rare or non-existent. Various levels of performance versus

cooling capacity are available and must be understood before designing a chassis. Automatic

thermal management must be used as part of the total system thermal solution.

The size and type of the heatsink, as well as the output of the fan can be varied to balance size,

cost, and space constraints with acoustic noise. This document has presented the conditions and

requirements for designing a heatsink solution for a system based on an Intel Pentium 4 processor

in the 478-pin package. Properly designed solutions provide adequate cooling to maintain the

processor thermal specification. This is accomplished by providing a low local ambient

temperature and creating a minimal thermal resistance to that local ambient temperature. Fan

heatsinks or ducting can be used to cool the processor if proper package temperatures cannot be

maintained otherwise. By maintaining the processor case temperature at the values specified in the

processor datasheet, a system designer can be confident of proper functionality and reliability of

these processors.