6. System Interface Operations

6.7 Cluster Bus


In a multiprocessor system using the cluster bus, the cluster coordinator performs the cluster bus arbitration and data flow management. The arbitration scheme assures that either one of the processors or the cluster coordinator is master at any given time, while the remaining devices are slave.

A processor request issued by the master processor is observed as an external request by all slave R10000 processors, as shown in Figure 6-1. Similarly, a processor coherency data response issued by a master processor is observed as an external data response by the slave processors.



Figure 6-1 Processor Request Master/Slave Status

In a multiprocessor system using the cluster bus, a mode bit specifies whether processor coherent requests are to target the external agent only, or all processors and the external agent. This allows systems with efficient snoopy, duplicate tag, or directory-based coherency protocols to be created.




Copyright 1995, MIPS Technologies, Inc. -- 29 JAN 96


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