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Abstract

A multiprocessor computer system which provides fault tolerance includes a number of processing sets. At least one of the processing sets is operable asynchronously of a second processing set. A monitor is connected to receive I/O operations output from the processing sets for identifying faulty operation of those units. The monitor is also operable to synchronize operation of the processing sets by signalling the processing sets on receipt of outputs from those units indicative of a plurality of them being at an equivalent stage of processing. The common monitor can be operable to determine not only faulty operation of the processing sets, but also to synchronize those units by monitoring the I/O operations output from the units. The monitor provides for buffering of I/O operations output from the processing sets and for selective forwarding of those I/O operations to an external I/O bus. A processing set may be formed from a single processor, or may be formed from multiple symmetric processors. A mutex ordering scheme can be provided to ensure deterministic access by the individual processors of the processing sets to local resources.

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First Claim