SSD: an affordable fault tolerant architecture for superscalar processors

The paper proposes an integrity checking architecture for superscalar processors that can achieve fault tolerance capability of a duplex system at much less cost than the traditional duplication approach. The pipeline of the CPU core (P-pipeline) is combined in series with another pipeline (V-pipeline), which re-executes instructions processed in the P-pipeline. Operations in the two pipelines are compared and any mismatch triggers the recovery process. The V-pipeline design is based on replication of the P-pipeline, and minimized in size and functionality by taking advantage of control flow and data dependency resolved in the P-pipeline. Idle cycles propagated from the P-pipeline become extra time for the V-pipeline to keep up with program re-execution. For a large-scale superscalar processor, the proposed architecture can bring up to 61.4% reduction in die area and the average-execution time increase is 0.3%