Method and apparatus for maintaining cache coherency in a computer system with a highly pipelined bus and multiple conflicting snoop requests

Claim 1

In a computer system including a plurality of caching agents and a bus coupling one or more of the plurality of caching agents to one another, a method of maintaining cache coherence, the method comprising the steps of: (a) monitoring the bus for a snoopable request, the snoopable request having an address associated with it, and responsive to finding the snoopable request; (i) allocating an entry in a snoop queue, the snoop queue having one or more entries, (ii) comparing the address of the snoopable request with one or more pending addresses stored in the snoop queue corresponding to one or more pending bus operations, (iii) setting a first block condition if there is a match between the address of the snoopable request and the one or more pending addresses stored in the snoop queue, and (iv) setting one or more history bits indicating a chronological ordering of the entry in the snoop queue; and (b) preventing one or more subsequent snoop operations from starting until the first block condition set in the step (a)(iii) is cleared.