The Unabridged Pentium 4 IA32 Processor Genealogy

FSB Agents

Agent Types

All devices that reside on the processor's FSB are referred to as agents. Basically, there are three type of agents:

• The Request Agent is the device that initiates a transaction by issuing a transaction request (e.g., a memory read or write, an IO read or write, etc.). It is also referred to as the transaction initiator.

• The Response Agent is the target of the transaction (e.g., an IO target or a memory target).

• The Snoop Agents (aka the snoopers) are any devices on the FSB that have memory caches (usually processors, but, as an example, in addition to the processors there could be an external cache that resides on the FSB). Whenever any initiator starts a transaction, the transaction request is latched by all FSB agents ...