Mips Tech Limited

Julian Bailey

Philip Day

Hardware structures for check pointing a main shift register one or more times which include a circular buffer used to store the data elements most recently shifted onto the main shift register which has an extra data position for each check point and an extra data position for each restorable point in time; an update history shift register which has a data position for each check point which is used to store information indicating whether the circular buffer was updated in a particular clock cycle; a pointer that identifies a subset of the data positions of the circular buffer as active data positions; and check point generation logic that derives each check point by selecting a subset of the active data positions based on the information stored in the update history shift register.

Check pointing a shift register with a circular buffer

A fault tolerant multi-threaded processor uses the temporal and/or spatial separation of instructions running in two or more different threads. An instruction is fetched, decoded and executed by each of two or more threads to generate a result for each of the two or more threads. These results are then compared using comparison hardware logic and if there is a mismatch between the results obtained, then an error or event is raised. The comparison is performed on an instruction by instruction basis so that errors are identified (and hence can be resolved) quickly.

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Julian Bailey