Recently many imprecise circuit design techniques have been proposed for implementation of error-tolerant applications, such as multimedia and communications. These algorithms do not mandate absolute correctness of their results, and imprecise circuit components can therefore leverage this relaxed fidelity requirement to provide performance and energy benefits. In this paper, several imprecise adder design techniques are classified and compared in terms of their error characteristics and power-delay efficiency. A general methodology for fidelity-efficiency design space exploration is presented and is applied to a case study implementing the CORDIC algorithm in 130nm technology. The case study reveals that simple precision scaling often provides better power-delay efficiency for a given fidelity than more complex imprecise adders, but different choice of algorithm and fidelity can influence the outcome.
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