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

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Assignment of IDs to the Processor

Introduction

At power-up time, each of the processors on the FSB must be assigned a unique ID that is output in any transaction initiated by the processor. This is referred to as its Agent ID. In addition, each processor contains a Local APIC module. This module must be assigned two addresses at startup time: a Cluster ID and a Local APIC ID.

The Cluster ID

The Purpose of the Cluster ID

In the Pentium® 4 processor family, interrupt messages are transferred over the FSB (the 3-wire APIC bus was eliminated). An interrupt message contains a destination address and one of the forms it can take is that of a Cluster ID and the ID of a Local APIC within a processor in the target cluster. For this reason, a Cluster ...

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