A Simple Yet Efficient Accuracy-Configurable Adder Design

Approximate computing is a promising approach for low-power IC design and has recently received considerable research attention. To accommodate dynamic levels of approximation, a few accuracy-configurable adder (ACA) designs have been developed in the past. However, these designs tend to incur large area overheads as they rely on either redundant computing or complicated carry prediction. Some of these designs include error detection and correction circuitry, which further increase the area. In this paper, we investigate a simple ACA design that contains no redundancy or error detection/correction circuitry and uses very simple carry prediction. The simulation results show that our design dominates the latest previous work on accuracy-delay-power tradeoff while using 39% lower area. In the best case, the iso-delay power of our design is only 16% of accurate adder regardless of degradation in accuracy. One variant of this design provides finer-grained and larger tunability than that of the previous works. Moreover, we propose a delay-adaptive self-configuration technique to further improve the accuracy-delay-power tradeoff. The advantages of our method are confirmed by the applications in multiplication and discrete cosine transform computing.