Area-Efficient Error Protection for Caches

Due to increasing concern about various errors, current processors adopt error protection mechanisms. Especially, protecting L2/L3 caches incur as much as 12.5% area overhead due to error correcting codes. Considering large L2/L3 caches of current processors, the area overhead is very high. This paper proposes an area-efficient error protection scheme for L2/L3 caches. First, it selectively applies ECC (error correcting code) to only dirty cache lines and other clean cache lines are protected using simple parity check codes. Second, the dirty cache lines are periodically cleaned by exploiting the generational behavior of cache lines. Experimental results show that the cleaning technique effectively reduces the number of dirty cache lines per cycle. The ECCs of this reduced number of dirty cache lines can be maintained in a small storage. Our proposed scheme is shown to reduce the area overhead of a 1MB L2 cache for error protection by 59% for SPEC2000 benchmarks running on a typical four-issue superscalar processor