Design for low power and power management in IBM Blue Gene/Q

In this paper, we explain the techniques used in IBM Blue Gene®/Q Compute chips to achieve high energy efficiency. Architectural techniques include the choice of a power-efficient, throughput-oriented processor core with a SIMD (single-instruction, multiple-data) floating-point unit, as well as multiple frequency domains for moving data. Design techniques include clock gating and the use of multiple threshold voltage devices. From a systems perspective, power is reduced by using a speed binning technique that characterizes the manufacturing variability of chips during wafer test, permitting similar chips to be packaged on the same board and run at the lowest voltage possible. We describe the techniques used to monitor and manage the power and performance of the various subunits of the Blue Gene/Q chip. Details include the functioning of the environmental monitor and the performance counters. Using these facilities, we describe the framework to understand how the chip's subunits contribute to the total active and leakage power consumed. A power characterization technique for the development of application-dependent power projection models is presented. Differences between estimated power before chip tape-out versus measured power are discussed.