Reevaluating fast dual-voltage power rail switching circuitry


Several recent papers have been published proposing the use of dual-voltage rails and fast switching circuitry to address bottlenecks or overcome process variation in near- threshold computing systems. The published results yield boosting transition times of 7-10ns, which, in some cases, is needed for the architectural contributions to be justified. However, the analysis of these circuits assumed incorrect core models, ideal off-chip power supplies, and non-worst case scenarios. When realistic bonding capacitance and inductance are included, proper core models are used, and worst-case simulation is performed these transitions times can be off by 3x, adversly impacting the potential gains in the system.In this paper we analyze the previously proposed de- signs, and propose a new design in order to achieve the de- sired transition time. By using a third internal power rail and some additional on-chip capacitors the supply voltage noise can be isolated from the main external power sup- plies. Ultimately the new circuit achieves the desired 10ns transition time, allowing the architectural contributions of the previous studies to still be attainable.

2012 Workshop on Duplicating, Decontructing and Debunking (WDDD)