This paper describes a novel strategy for generating accurate black-box models of datapath power consumption at the architecture level. This is achieved by recognizing that power consumption in digital circuits is affected by activity, as well as physical capacitance. Since existing strategies characterize modules for purely random inputs, they fail to account for the effect of signal statistics on switching activity. The Dual Bit Type (DBT) model, however, accounts not only for the random activity of the least significant bits (LSB's), but also for the correlated activity of the most significant bits (MSB's), which contain two's-complement sign information. The resulting model is parameterizable in terms of complexity factors such as word length and can be applied to a wide variety of modules ranging from adders, shifters, and multipliers to register files and memories. Since the model operates at the register transfer level (RTL), it is orders of magnitude faster than gate-or circuitlevel tools, but while other architecture-level techniques often err by 50-100% or more, the DBT method offers error rates on the order of 10-15%. Index Terms-High-level design tools, library characterization, low power, power estimation, statistical modeling.

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The growing demand for portable electronic devices has led to an increased emphasis on power consumption within the semiconducror industry. As a result, designers are now encouraged to consider the impact of their decisions not only on speed and area, but also on power throughout the entire design process. In order to evaluate how well a particular design variant meets power constraints, engineers often rely on CAD tools for power estimation. While tools have long existed for analyzing power consumption at the lower levels of abstraction -e.g. SPICE and PowerMillonly recently have efforts been directed towards developing a high-level power estimation capability. This paper surveys the state of the art in high-level power estimation, addressing techniques that operate at the architecture, behaviol; instruction, and system levels of abstraction.

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