Fault-tolerant Last Level Cache Architecture Design at Near-threshold Voltage
LIU Wei①② WEI Zhigang① DU Wei①② CAO Guangyi① WANG Wei③
①(College of Computer Science and Technology, Wuhan University of Technology, Wuhan 430070, China) ②(Hubei Key Laboratory of Transportation Internet of Things, Wuhan 430070, China) ③(Department of Computer Science and Technology, Tongji University, Shanghai 200092, China)
Abstract：Near-threshold voltage computing enables transistor voltage scaling to continue with Moore’s Law projection and dramatically improves power and energy efficiency. However, a great number of bit-cell errors occur in large SRAM structures, such as Last-Level Cache (LLC). A Fault-Tolerant LLC (FTLLC) design with conventional 6T SRAM cells is proposed to deal with a higher failure rate which is more than 1% at near-threshold voltage. FTLLC improves the reliability of data stored in Cache by correcting the single-error and compressing multi-errors in Cache entry. To validate the efficiency of FTLLC, FTLLC and prior works are implemented in gem5, and are simulated with SPEC CPU2006. The experiment shows that compared with Concertina at 650 mV, the performance of a 65 nm FTLLC with 4-Byte subblock size improves by 7.2% and the Cache capacity increases by 24.9%. Besides, the miss rate decreases by 58.2%, and there are little increases on area overhead and power consumption.
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