CACHE COHERENCY PROTOCOLS WITH GLOBAL AND LOCAL POSTED OPERATIONS

A method of avoiding deadlocks in cache coherency protocol for a multi-processor computer system, by loading a memory value into a plurality of cache blocks, assigning a first coherency state having a higher collision priority to only one of the cache blocks, and assigning one or more additional coherency states having lower collision priorities to all of the remaining cache blocks. Different system bus codes can be used to indicate the priority of conflicting requests (e.g., DClaim operations) to modify the memory value. The invention also allows folding or elimination of redundant DClaim operations, and can be applied in a global versus local manner within a multi-processor computer system having processing units grouped into at least two clusters.