Parameter variation in scaled technologies beyond 90nm will pose a major challenge for design of future high performance microprocessors. In this paper, we discuss process, voltage and temperature variations; and their impact on circuit and microarchitecture. Possible solutions to reduce the impact of parameter variations and to achieve higher frequency bins are also presented. Categories and Subject Descriptors B.7.1 Microprocessors and microcomputers, VLSI. General Terms: Design, Performance, Reliability.