SimTag: Exploiting tag bits similarity to improve the reliability of the data caches

Abstract

Though tag bits in the data caches are vulnerable to transient errors, few effort has been made to reduce their vulnerability. In this paper, we propose to exploit prevalent same tag bits to improve error protection capability of the tag bits in the data caches. When data are fetched from the main memory, it is checked if adjacent cache lines have the same tag bits as those of the data fetched. This similarity information is stored in the data caches as extra bits to be used later. When an error is detected in the tag bits, the similarity information is used to recover from the error in the tag bits. The proposed scheme has small area, energy, and performance overheads with error protection coverage of 97.9% on average. In contrast, the previously proposed InCache Replication scheme is shown to incur large performance and energy overheads.