Method and system for communicating tags of data access target and castout victim in a single data transfer

摘要

A combined address bus transaction contains the address tag for a data access operation target, the address tag for a victim to be replaced, and the address index field identifying the congruence class including both the target and the victim. Directory state information such as coherency state and/or LRU position for the cast out victim may also be appended to the index field and target and victim address tags within the bus operation. Address bus bandwidth utilization is thereby improved, eliminating duplicate transmission of the index field employed by separate data access and cast out operations in accordance with the existing practice. The victim may be prospectively selected concurrently with the determination of whether the target may be found within the storage device forming the combined address, improving overall performance for that device.