A Dynamically Adjusting Gracefully Degrading Link-level Fault-tolerant Mechanism for NoCs
File(s)
Journal
IEEE Transactions on Computer-Aided Design of Integrated Circuits and Systems
Date Issued
August 2012
Abstract
The rapid scaling of silicon technology has enabled massive transistor integration densities. Nanometer feature sizes, however, are marred by increasing variability and susceptibility to wear-out. Billion-transistor designs, such as chip multiprocessors (CMPs), are especially vulnerable to defects. CMPs rely on a network-on-chip for all their communication needs. A single link failure within this on-chip fabric can impede, halt, or even deadlock, intertile communication, which can render the entire chip multiprocessor useless. In this paper, we present a technique capable of handling very large numbers of permanent wire failures that occur in parallel links either at manufacture-time or at runtime (dynamically). As opposed to marking an entire parallel link as faulty, whenever some wires fail, the proposed methodology employs these partially-faulty links (PFLs) to continue the transfer of information-albeit at a gracefully degraded mode-in order to maintain network connectivity. Furthermore, the presented technique can designate PFLs as fully-faulty when several wires fail, by utilizing appropriate routing algorithms that bypass nonoperational links, while still maintaining load-balance in the vicinity of PFLs. The proposed scheme employs architectural support within the on-chip routers to detect link failures and enable reconfiguration at the granularity of individual wires. Hardware synthesis confirms the low-cost nature of the proposed architecture, and full-system simulations using both synthetic network traffic and real workloads demonstrate its efficacy