ERrOR: Improving Performance and Fault Tolerance using Early Execution

Contemporary integrated circuits are becoming increasingly susceptible to soft errors due to single-event upsets, effectively decreasing the reliability of operation. In this paper, we propose the ERrOR microarchitecture, that detects soft errors in processor operation using temporal redundancy with minimal hardware overhead. Previous proposals have explored the idea of introducing an Early Execution Unit (EXU) at the processor frontend in order to expeditiously execute dynamic instructions with short dependency chains for performance improvement. However, we observe that the functional units in the EXU are idle for a significant fraction of the program execution duration. ERrOR leverages these inactive frontend functional units to re-execute dynamic instructions for the purpose of error detection. A lightweight verifier introduced at the backend makes use of idle resources for redundant execution by interleaving program execution with re-execution for error detection. ERrOR provides exhaustive transient fault coverage while improving performance by 7.5% over an existing restricted OoO microarchitecture, Freeflow Core.