The Unabridged Pentium 4 IA32 Processor Genealogy

The Snoop Phase Has Two Purposes

In the Snoop Phase, the Request Agent samples the snoop result signals to determine two things:

1. If the currently-addressed Response Agent (i.e., the target) intends to complete the transaction now or it intends to issue a Retry or a Deferred response when the transaction reaches its Response Phase.

2. If the transaction is a memory read or write that the Response Agent will complete now (i.e., it doesn't intend to defer its completion), does any other cache have a copy of the line and, if so, in what state will its line be at the completion of the transaction (clean or modified)?

The reader should also remember that the snoop signals are being sampled by all FSB agents so as to remain synchronized with the state of ...