This text constitutes the thoroughly refereed post-proceedings of the First International Workshop on Power-Aware Computer Systems, PACS 2000, held in Cambridge, Massachusetts, USA, in November 2000. The 11 revised full papers presented were carefully reviewed, selected and revised for inclusion in the book. This book addresses power/energy-awareness at all levels of computer systems. The papers are organized in sections on power-aware microarchitectural/circuit techniques, application/compiler optimization, exploiting IPC/memory slack, and power/performance models and tools.