Real-Time Minimum Energy Point Tracking Using a Predetermined Optimal Voltage Setting Strategy

Minimizing the energy consumption of processors for a given computational workload is highly desired for matured and energy efficient, information oriented society. In this paper, we refer to a pair of the supply voltage (VDD) and threshold voltage (VTH), which minimizes the energy consumption of the processor under a given computational workload, as a minimum energy point (MEP in short). Since always running at the MEP largely reduces the energy consumption of processors without fundamental degradation of the performance, a lot of methods for tracking the MEP at runtime have been investigated over the past several years. However, to the best of our knowledge, all the previous methods are based on time-consuming power measurement to identify the MEP at runtime, which prevents the real-time tracking of the MEP. This paper proposes a real-time MEP tracking method based on a predetermined MEP-curve which is characterized as a linear model for each chip at a boot phase. Experimental results obtained using a 50-stage fanout-4 inverter chain designed to reflect the behavior of a microprocessor pipeline demonstrate that the energy loss introduced by the linear approximation MEP model is only 3.1% at the worst case.