Extremely Low Cost Error Protection with Correctable Parity Protected Cache

Due to shrinking feature sizes, processors are becoming more vulnerable to soft errors. One of the most vulnerable components of a processor is its write-back cache. This paper proposes a new reliable write-back cache called Correctable Parity Protected Cache (CPPC), which adds correction capability to parity protection. In CPPC, parity bits detect faults and the XOR of all data written into the cache is kept to recover from detected faults. The added correction scheme provides a high degree of reliability and corrects both single and spatial multi-bit faults in exchange for very small performance and power overheads. CPPC is compared to competitive schemes. Our simulation data show that CPPC improves reliability significantly while its overheads are very small, especially in the L2 cache.