MSI State Diagram for a Local Cache g Three states for a cache block in a local (private)cache similar to snooping coherence protocol CPU read hit g Requests by processor validate/ Acknowledge CPU read /Read miss message ☆B| ack arrows Invalid Shared (read only) Requests by directory CPU write ☆ Red arrows E∽E Modified (read/write CPU read hit CPU write miss/ CPU write hit Write-back, Write-miss message 2021/22 计算机体系结构MSI State Diagram for a Local Cache 2021/2/2 计算机体系结构 18