Near/Sub-Threshold Circuits and Approximate Computing: The Perfect Combination for Ultra-Low-Power Systems
Near/Sub-Threshold Circuits and Approximate Computing: The Perfect Combination for Ultra-Low-Power Systems
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近/亚阈值电路和近似计算：超低功耗系统的完美组合
DOI：
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发表时间：
2015
期刊：
影响因子：
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通讯作者：
C. Enz
中科院分区：
文献类型：
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作者：
Jeremy Schlachter;Vincent Camus;C. Enz
虽然亚/近阈值设计提供了最小的功率和能量消耗，但这种方法严重恶化了电路性能和对PVT（工艺/电压/温度）变化的鲁棒性，导致巨大的速度损失和大的硅面积。不精确和近似的电路设计可以通过牺牲计算精度来获得更好的硅面积、电路速度甚至更好的功耗来解决这些问题。本文综述了两种适用于算术电路的近似计算技术：门级剪枝和进位推测，并提出了改进意见。一个关键的研究，然后进行考虑几个错误的度量，并为第一次，这些技术相结合，以产生近似加法器，在类似的错误水平，甚至更高的增益。然后表明，这些技术可以应用于亚阈值库，以减轻大的可变性。
While sub/near-threshold design offers the minimal power and energy consumption, such approach strongly deteriorates circuit performances and robustness against PVT (process/voltage/temperature) variations, leading to gigantic speed penalties and large silicon areas. Inexact and approximate circuit design can address these issues by trading calculation accuracy for better silicon area, circuit speed and even better power consumption. This paper reviews and proposes improvements for two approximate computing techniques applicable to arithmetic circuits: gate-level pruning and carry speculation. A critical study is then carried out considering several error metrics, and for the first time, those techniques are combined to produce approximate adders showing even higher gains at similar error levels. It is then shown that those techniques can be applied to a sub-threshold library to mitigate the large variability.