Reliability and performance tunable architecture: the partially asynchronous R-Fold modular redundancy (pA-RMR)

Abstract

The R-fold modular redundancy (RMR) is a widely known fault-tolerant architecture based on hardware redundancy. It improves the system reliability by replicating the basic computing element and combining all the results with a majority criterion. In this analytic study, we extend this conventional approach by introducing the time dimension in the RMR design. Indeed, the asynchronous nature of future nanoelectronic computing systems is taken into account by introducing the partially asynchronous RMR (pA-RMR) structure whose main feature is to detect the arrival of each input signal from the replicas based on the use of tokens. The voter behavior is modified in such a way that it sets the output result after a determined number of token arrivals. By doing this, we are adding a second degree of freedom to the RMR structure, which not only has a configurable size (R replicas), but also allows modifying the number of tokens it waits before giving an output. As a consequence of this seemingly simple change, we are able to exploit new possibilities of this redundant structure. This second degree of freedom allows choosing between system reliability and performance during operation. The number of available replicas in the pA-RMR architecture determines the maximum reliability achievable, while the voting policy allows us to adapt the structure to different design requirements and achieve the desired balance between reliability and performance.