1. Low Power Design: An Introduction

Through most of the evolution of the electronics and computer industry in the twentieth century, technological progress was defined in terms of the inexorable march of density and speed. Increasing density resulted from process improvements that led to smaller and smaller geometries of semiconductor devices, so the number of transistors packed into a given area kept increasing. Increasing processing speed indirectly resulted from the same causes: more processing power on the same chip meant more computation resources and more data storage on-chip, leading to higher levels of parallelism and hence, more computations completed per unit time. Circuit and architectural innovations were also responsible for the increased speed. In the case of processors, deeper pipelines and expanding parallelism available led to improvements in the effective execution speed. In the case of memories, density continued to make remarkable improvements; performance improvements were not commensurate, but nevertheless, architectural innovations led to increased bandwidth at the memory interface.