COMPUTER CACHE SYSTEM WITH DEFERRED INVALIDATION

A lower level cache detects when a line of memory has been evicted from a higher level cache. The lower level cache stores the address of the evicted line. When the system bus is idle, the lower level cache initiates a transaction causing all higher level caches to invalidate the line. The lower level cache then places the line into a special state. If a line in the special state is evicted from the lower level cache, the lower level cache knows that the line is not cached at a higher level, and therefore a back-invalidate transaction is not needed.