A memory system for reducing cache snooping overhead for a two level cache system with multiple bus masters, has a level 2 cache connected to a main memory and a level 1 cache connected to a bus master. Each bus master has one level 1 cache assigned to it. A shared level 2 cache is connected to each...http://www.google.com/patents/US5796980?utm_source=gb-gplus-sharePatent US5796980 - Reducing cache snooping overhead in a multilevel cache system with inclusion field in shared cache indicating state of data in lower level caches 
