Fault-tolerant features in the HaL memory management unit

This paper describes fault-tolerant and error detection features in HaL's memory management unit (MMU). The proposed fault-tolerant features allow recovery from transient errors in the MMU. It is shown that these features were natural choices considering the architectural and implementation constraints in the MMU's design environment. Three concurrent error detection and correction methods employed in address translation and coherence tables in the MMU are described. Virtually-indexed and virtually-tagged cache architecture is exploited to provide an almost fault-secure hardware coherence mechanism in the MMU, with very small performance overhead (less than 0.01% in the instruction throughput). Low overhead linear polynomial codes have been chosen in these designs to minimize both the hardware and software instrumentation impact.<
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