Abstract-Power switches are used as part of power-gating technique to reduce leakage power of a design. To the best of our knowledge, this is the first work in open-literature to show a systematic diagnosis method for accurately diagnosing power switches. The proposed diagnosis method utilizes recently proposed DFT solution for efficient testing of power switches in the presence of PVT variation. It divides power switches into segments such that any faulty power switch is detectable thereby achieving high diagnosis accuracy. The proposed diagnosis method has been validated through SPICE simulation using a number of ISCAS benchmarks synthesized with a 90-nm gate library. Simulation results show that when considering the influence of process variation, the worst case loss of accuracy is less than 4.5%; and the worst case loss of accuracy is less than 12% when considering VT (Voltage and Temperature) variations.Index Terms-Sleep transistor, diagnosis, power gating, leakage power management, design for test (DFT).
Digital circuits are currently designed to ensure timing closure. Releasing this constraint by allowing timing violations could lead to significant performance improvements, but conventional forms of computer arithmetic do not fail gracefully when pushed beyond deterministic operation. In this paper we take a fresh look at Online Arithmetic, originally proposed for digit serial operation, and synthesize unrolled digit parallel online operators to allow for graceful degradation. We quantify the impact of timing violation on key arithmetic primitives, and show that substantial performance benefits can be obtained in comparison to binary arithmetic. Since timing errors are caused by long carry chains, these result in errors in least significant digits with online arithmetic, causing less impact than conventional implementations. Using analytical models and empirical FPGA results from an image processing application, we demonstrate an error reduction over 89% and an improvement in SNR of over 20dB for the same clock rate.
Abstract-Embedded applications can often demand stringent latency requirements. While high degrees of parallelism within custom FPGA-based accelerators may help to some extent, it may also be necessary to limit the precision used in the datapath to boost the operating frequency of the implementation. However, by reducing the precision, the engineer introduces quantization error into the design. In this paper, we demonstrate that for many applications it would be preferable to simply overclock the design and accept that timing violations may arise. Since the errors introduced by timing violations occur rarely, they will cause less noise than quantization errors. Through the use of analytical models and empirical results on a Xilinx Virtex-6 FPGA, we show that a geometric mean reduction of 67.9% to 98.8% in error expectation or a geometric mean improvement of 3.1% to 27.6% in operating frequency can be obtained using this alternative design methodology.
Abstract-Relaxing constraints of 100% accuracy in datapath can provide the freedom to create designs with better performance or energy efficiency. This paper develops probabilistic models, which enable us to explore these trade-offs for key arithmetic primitives. We show that because specific input patterns are required to cause timing violations and that these patterns arise rarely, a lower expected error can be attained by allowing some timing variations to occur, instead of reducing the precision of a circuit to meet a target latency. Experiments show that a mean reduction of 5.6× ∼ 36.7× in error expectation and an improvement of 7.2 ∼ 19.7 in signal-to-noise ratio can be obtained for practical applications.
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