cluster request buffer. This buffer maintains the status of the eight possible outstanding requests on the System interface. When the System interface is in master state, and it issues the address cycle of processor read or upgrade request, the processor places an entry into the cluster request buffer. When the System interface is in slave state, and an external agent issues an external coherency or allocate request number request, it places an entry into the cluster request buffer.
Once an entry is placed into the cluster request buffer, the associated request number transitions from free to busy. An entry remains busy until the processor receives an external completion response. Processor requests that are ready to be issued to the System interface bus probe the cluster request buffer to detect conflict conditions.
