Reduction of power dissipation in microprocessor design is becoming a key design constraint. This is motivated not only by portable electronics, in which battery weight and size is critical, but by heat dissipation issues in larger desktop and parallel machines as well. By identifying the major modes of computation of these processors and by proposing figures of merit for each of these modes, a power analysis methodology is developed. It allows the energy efficiency of various architectures to be quantified, and provides techniques for either individually optimizing or trading off throughput and energy consumption. The methodology is then used to qualify three important design principles for energy-efficient microprocessor design.