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The Unabridged Pentium 4 IA32 Processor Genealogy by Bob Colwell, Tom Shanley

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The Thermal Monitoring Facilities

Introduction to Thermal Monitoring

The Pentium® 4 processor incorporates three thermal monitoring mechanisms:

  • The Catastrophic Shutdown Detector stops processor execution (by turning off all internal clocks) when the processor's core temperature rises above a preset limit. It is not programmable and is always enabled.

  • The hardware-based Automatic Thermal Monitoring facility forces the processor to decrease its performance when the core temperature rises above a preset level.

  • The Software Controlled Clock Modulation mechanism allows software to decrease processor performance to lower the core temperature.

Thermal Monitor Feature Detection

The Thermal Monitoring facilities are detected by executing a CPUID request ...

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