Two-Dimensional Protection Code for Virtual Page Information in Translation Lookaside Buffers

Abstract

Severe conditions such as high-energy particle strikes may induce soft errors in on-chip memory, like cache and translation lookaside buffers (TLBs). As the key component of virtual-to-physical address translation, TLB directly affects processor performance. To protect the virtual page information stored in TLB, several studies have introduced error detection or correction codes. However, most schemes proposed for data TLB cannot support the detection of multi-bit upsets, which is reported as a serious issue in modern fault-tolerant processors due to the downscaling of CMOS process technology. In this paper, we propose a new two-dimensional protection technique, called the matrix protection tag (MaP-Tag), to provide stronger error detection and correction capability to TLB virtual page information. Our proposal reorganizes virtual page information into a matrix and employs adjacent check bits and interleaved check bits for error detection. The two-dimensional design offers one-bit error detection, burst multi-bit error detection, and even multi-bit error correction in some cases. The simulation results show that our proposal can detect almost all error patterns when injected with up to eight bit-flips. Furthermore, the technique provides a better error correction rate than conventional single error correction (SEC) codes. The reliability calculation shows that our proposal is powerful in both error detection and correction with affordable storage overhead.