Improving the Performance of GALS-Based NoCs in the Presence of Process Variation

Abstract

Current integration scales allow designing chip multiprocessors (CMP) where cores are interconnected by means of a network-on-chip (NoC). Unfortunately, the small feature size of current integration scales cause some unpredictability in manufactured devices because of process variation. In NoCs,variability may affect links and routers causing that they do not match the parameters established at design time. In this paper we first analyze the way that manufacturing deviations affect the components of a NoC by applying a comprehensive and detailed variability model to 200 instances of an 8x8 mesh NoC synthesized using 45nm technology. A second contribution of this paper is showing that GALS-based NoCs present communication bottlenecks under process variation. To overcome this performance reduction we draft a novel approach, called performance domains, intended to reduce the negative impact of variability on application execution time. This mechanism is suitable when several applications are simultaneously running in the CMP chip.