Variability Expeditions: A Retrospective

Expeditions in Computing are among the largest and most ambitious projects sponsored by the National Science Foundation that seek to explore far out ideas in computing with potential for significant impact on computing and its industry. In 2009, we conceived of an Expeditions project in response to an alarming trend in the semiconductor industry: the manufactured chips were demonstrating significant variation in their performance and power consumption that was increasing at a rapid pace, leading designers to overdesign circuits with margins (e.g., margins on speed and voltage, also referred to as guard bands) that often exceeded 40% of the nominal target specifications. This overdesign threatened to make new process nodes ineffective by causing significant loss of yield, effectively wiping out gains due to scaling geometries. In addition to manufacturing, computing machines were experiencing increasing variation in operating conditions due to the proliferating use of these devices in mobile and wireless applications.