In Simultaneous Multi-Threading (SMT) chip multiprocessors (CMPs), thread placement is performed today in a largely power-unaware manner. For example, consolidation of active threads into fewer cores exposes opportunities for power savings that have not been addressed in prior work. The savings opportunity is especially high in the emerging context where percore power gating (PCPG) is becoming viable. The use of the optimum combination of core-wise SMT level and number of active cores to achieve a desired power-performance efficiency is a knob which has not been explored in prior work nor implemented as part of the operating system task scheduler. © 2013 IEEE.