Sixer: A low-overhead, fully-distributed test scheme with guaranteed delivery of packets in networks-on-chip

Abstract

The guaranteed delivery of application packets from source to destination in a network-on-chip (NoC) is increasingly becoming an essential design issue. Channel faults may cause a significant amount of packet loss and subsequently degrade the system’s performance. In particular, open-channel defects threaten the loss of reliability, yield, and service quality. Hence, their detection and localization during the system’s runtime are highly needed. However, coexistent short-channel faults might mitigate the threats to a certain extent. This paper presents a low-cost test method that detects open-channel faults to preserve the connectivity between a source and destination pair in NoCs. The procedure is extended to address the channel’s self-repairing mode by covering the short-channel defects via fault masking. Further, a fully distributed test-scheduling technique named “Sixer” is presented to reduce the test cost and make the scheme scalable with NoCs. Experimental results show hardware synthesis incurs nearly 6.72% and 21.85% area overhead while single and multiple channel-fault models are assumed, respectively. The test method takes 8 and 38 clocks for the same fault models. Also, fault simulation shows full and (nearly 95%) fault coverage for these models. Online evaluation of the “Sixer” reveals various performance metrics. A detailed comparison study shows the proposed scheme improves hardware area and test-time overhead up to 66.12% and 97%, respectively. Simultaneously, performance overhead is improved by 43.78%, 54.75%, and 62.97% concerning packet loss, latency, and energy consumption, respectively.