Flexible on-chip power delivery for energy efficient heterogeneous systems

Heterogeneous systems-on-chip pose a challenge for power delivery given the variety of needs for different components. In this paper, we describe recent work that leverages power switches and conventional EDA toolflows to implement a set of power delivery schemes that provide a flexible, adaptable range of options for power management of SoCs for which energy efficiency is important. We first present an enhanced dynamic voltage scaling (DVS) scheme that uses power switches to provide rapid changes in the energy-speed operating point to match workloads at a component level. To demonstrate this approach, we describe a data flow processor chip in 90nm CMOS that supports flexible operation from 0.25V with super high energy efficiency up to GHz speeds at 1.2V. This chip shows that our low overhead method to scale energy consumption with the performance requirement supports both high performance and ultra low energy (>10X reduction in energy per operation) in the same circuit. We discuss power switch design for this scheme and investigate strategies for optimizing power switches for different operating modes. Finally, we show how segmented power switches offer several advantages for flexibly managing leakage and for modulating local voltages with low overhead.