Read Operation
Local Cluster : allocated RAC entry, send Read-req message to home cluster
Home Cluster: Assume directory entry in dirty state, forward to Read-Req to ‘owning’ remote cluster
Remote Cluster : Read data from owning processor
Remote Cluster: Send data to local cluster, send status of Sharing-Writeback to home cluster
Local Cluster: RAC entry updated, CPU arbitration released; CPU retries read and gets data
Home Cluster: Update directory entry to Shared state.