A cache protocol for error detection and recovery in fault-tolerant computing systems

We propose an error detection and recovery protocol for redundant processor systems employing caches. The protocol allows cache-based systems to vote more often and thereby reduce the chance of losing synchronization. The scheme is based on cache data broadcasting of a dirty line after modification. The scheme effectively exploits the redundancy of a fault-tolerant system using hardware voting. It recovers from erroneous data written by a processor and this remedies the insufficiency of error-correcting codes. The protocol can also be used to speed-up resynchronization process for a temporarily failed processor in a redundant system. More than 60% of cache lines are fully covered for recovery due to errors originated from the cache itself, including unrecoverable ECC errors. The performance overhead is to broadcast only 2-3% of the total memory references.<>