Cache block replacement scheme based on directory control bit set/reset

Abstract

A cache controller for a multithreading multiprocessor system which starts an execution of another thread by suspending an ongoing execution of a thread when a cache miss happens. The cache controller comprises a cache directory unit for storing cache managing data including a footprint bit to indicate a mapping relation between at least one cache block in a main memory block, an access control unit for searching the directory unit based on an access requesting message inputted thereto through its input/output port connected to a processor to return one of a cache hit notice and a cache miss notice, as well as transferring messages with the main memory through its input/output port connected to a network, and a footprint bit changing device for setting the footprint bit in the cache managing data corresponding to a cache block at a cache hit, while resetting the footprint bit upon input of a positive responding message through the input/output port connected to the network to a fetch requesting message which has been sent therethrough at a cache miss.