Method for data bus snooping in a data processing system by selective concurrent read and invalidate cache operation

摘要

A bus snoop control method for maintaining coherency between a write-back cache and main memory during memory accesses by an alternate bus master. The method and apparatus incorporates an option to source 'dirty' or altered data from the write-back cache to the alternate bus master during a memory read operation, and simultaneously invalidate 'dirty' or altered data from the write-back cache. The method minimizes the number of cache accesses required to maintain coherency between the cache and main memory during page-out/page-in sequences initiated by the alternate bus master, thereby improving system performance.