System and method of implementing read resources to maintain cache coherency in a multiprocessor environment permitting split transactions

Claim 1

A read resource system for maintaining cache coherency in a multiprocessor environment pertaining split transactions, having a plurality of nodes coupled by a main system bus, comprising: a plurality of read resources; and a plurality of read resource controllers coupled to the main system bus, each of said plurality of read resource controllers being uniquely associated with a respective one of the plurality of nodes, each read resource controller comprising: means for storing said plurality of read resources in a plurality of storage elements wherein said read resources are numbered and stored in said storage elements according to numerical order, means for receiving a read request for data from one of the plurality of nodes uniquely associated with said read resource controller, means for comparing said read request with contents of said plurality of storage elements to determine whether a previous read request is concurrently seeking said data, means for broadcasting onto the main system bus said read request if said data is not concurrently sought by said previous read request, means for allocating one of said plurality of read resources to prevent the broadcast of a successive read request that seeks said data concurrently with a broadcasted read request, wherein said allocated read resource is a multi bit tag address corresponding to said data, and means for storing an allocated read resource in one of said plurality of read resources, wherein said plurality of read resource controllers determines the number of allocated read resources independently according to a predetermined protocol, such that said plurality of read resource controllers calculates an equivalent number.

Claim 11

A method for maintaining cache coherency in a multiprocessor environment permitting split transactions, having a plurality of nodes coupled by a main system bus, comprising the steps of: providing a plurality of read resource controllers, each of said plurality of read resource controllers being uniquely associated with a respective one of the plurality of nodes; providing a plurality of storage elements in said plurality of read resource controllers; receiving a read request for data in one of the plurality of nodes; comparing said read request with the contents of said plurality of storage elements to determine whether a previous read request is currently seeking said data; broadcasting onto the main system bus said read request if said data is not concurrently being sought by said previous read request; allocating one of said plurality of read resources to protect said read request if said read request was broadcast onto the main system bus; and storing an allocated read resource comprising a multi-tag address corresponding to said data according to a read resource number in one of said plurality of storage elements in each read resource controller, wherein said read resource number is determined independently according to a predetermined protocol, such that each node arrives at an equivalent number.

Claim 12

A method for maintaining cache coherency in a multiprocessor environment permitting split transactions, having a plurality of nodes coupled by a main system bus, comprising the steps of: providing a plurality of read resource controllers, each of said plurality of read resource controllers being uniquely associated with a respective one of the plurality of nodes; providing a plurality of storage elements in said plurality of read resource controllers; receiving a read request for data in one of the plurality of nodes; comparing said read request with the contents of said plurality of storage elements to determine whether a previous read request is currently seeking said data; broadcasting onto the main system bus said read request if said data is not concurrently being sought by said previous read request; allocating one of said plurality of read resources to protect said read request if said read request was broadcast onto the main system bus; and storing an allocated read resource comprising a multi-tag address corresponding to said data according to a read resource number in one of said plurality of storage elements in each read resource controller, wherein said read resource number is determined independently according to a predetermined protocol, such that each node arrives at an equivalent number.