The recent paradigm shift to multi-core systems results in high system throughput within a specified power budget. However, future systems still require good single thread performance--no longer the predominant design priority--to mitigate sequential bottlenecks and/or to guarantee service-level agreements. Unfortunately, near saturation in voltage scaling necessitates a long-term alternative to dynamic voltage and frequency scaling. We propose an energy-proportional computing infrastructure, called WiDGET, that decouples thread context management from a sea of simple execution units (EUs). WiDGET's decoupled design provides flexibility to alter resource allocation for a particular power-performance target while turning off unallocated resources. In other words, WiDGET enables dynamic customization of different combinations of small and/or powerful cores on a single chip, consuming power in proportion to the delivered performance. Over all SPEC CPU2006 benchmarks, WiDGET provides average per-thread performance that is 26% better than a Xeon-like processor while using 8% less power. WiDGET can also scale down to a level comparable to an Atom-like processor, turning off resources to reduce average power by 58%. WiDGET achieves high power efficiency (BIPS3/W), exceeding Xeon-like and Atom-like processors by up to 2x and 21x, respectively.