Out-of-order execution significantly increases the performanceof superscalar processors. The out-of-order execution mechanismis, however, energy-inefficient,which inhibits scaling superscalar processorsto high issue widths and large instruction windows.\\\\%In this paper, we build on the observation that between 19% and 36%of the instructions are immediately ready for execution,even before entering the issue queue.Yet, these instructions proceed to the energy-consuming steps ofinstruction wake-up and select and they needlessly occupy space in theissue queue.To save energy, we propose for these instructions to by-pass theout-of-order execution core. Instead, we execute them on an energy-efficientsingle-issue in-order by-pass pipeline.The by-pass pipeline executes a significant fraction of all instructions,allowing performance-energy trade-offs with respect to the issue widthof the out-of-order pipeline and to the issue queue size.By making these trade-offs, we show energy reductions of53% for the issue queue, 33% for the register file and 31% in thewrite-back and wake-up logic.Performance remains almost unaffected.