Access Regulation to Hot-Modules in Wormhole NoCs

Network on chip (NoC) may be the primary interconnect mechanism for future systems-on-chip (SoC). Real-life SoCs typically include hot-modules such as DRAM controller or floating point unit, which are bandwidth limited and in high demand by other units. In this paper we demonstrate that the mere existence of one or more hot-modules in a wormhole-based NoC dramatically reduces network efficiency and causes an unfair allocation of system resources. We demonstrate that a single hot-module destroys the performance of the entire SoC, even if network resources are over-provisioned. In order to resolve the hot-module effect, we introduce a novel low-cost credit based distributed access regulation technique that fairly allocates access rights to the hot-module. Unlike other methods, this technique directly addresses the root cause of network buffer congestion phenomena. Using simulation, we show the effectiveness of the suggested mechanism in various NoC scenarios