| 摘要 |
Only a single snooper queue for global operations within a multiprocessor system is implemented within each bus snooper, controlled by a single token allowing completion of one operation. A bus snooper, upon detecting a combined token and operation request, begins speculatively processing the operation if the snooper is not already busy. The snooper then watches for a combined response acknowledging the combined request or a subsequent token request from the same processor, which indicates that the originating processor has been granted the sole token for completing global operations, before completing the operation. When processing an operation from a combined request and detecting an operation request (only) from a different processor, which indicates that another processor has been granted the token, the snooper suspends processing of the current operation and begins processing the new operation. If the snooper is busy when a combined request is received, the snooper retries the operation portion of the combined request and, upon detecting a subsequent operation request (only) for the operation, begins processing the operation at that time if not busy. Snoop logic for large multiprocessor systems is thus simplified, with conflict reduced to situations in which multiple processors are competing for the token.
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