ACM Transactions on Architecture and Code Optimization (TACO), 8(3):17:1~17:29, October 2011.
Advances in deep submicron technology call for a careful review of existing cache designs and design practices in terms of yield, area, and performance. This paper presents a Design and Evaluation Framework for defect-tolerant CAche Memories (DEFCAM), which enables processor architects to consider yield, area, and performance together in a unified framework. Since there is a complex, changing trade-off between these metrics depending on the technology, the cache organization, and the yield enhancement scheme employed, such a design flow is invaluable to processor architects when they assess a design and explore the design space quickly at an early stage. We develop a complete framework supporting the proposed DEFCAM design flow, from injecting defects into a wafer to evaluating program performance of individual processors on the wafer. Using DEFCAM, interesting interactions between architectural, organizational, and layout/defect related parameters can be easily evaluated. Moreover, we propose practical set remapping schemes to contain hard faults in cache memory. In a set remapping scheme, accesses that would go to an unusable faulty set are directed to a sound set. Case studies are presented to demonstrate the effectiveness of the proposed design flow and developed tools. Experimental results show that a set remapping is the most efficient fault covering method among prevailing strategies.