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This paper explores voltage scaling techniques for significant power reduction while maintaining performance. Detailed survey, IBM Blue Gene case study, and enablement strategies are covered to achieve up to 8x power efficiency improvement without performance loss.
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Practical Strategies forPower-Efficient ComputingTechnologies Karim Al-Sheraidah December 8th 2011
Overview • Survey of Power reduction techniques • ~8x improvement in power efficiency • No performance lose • Voltage Scaling • Optimum VDD = 0.5V • IBM Blue Gene system
Introduction • The Regime of interest
Introduction cont… Pactive = Ceff V2 ƒ + Ileak V Ceff is V dependent Ceff V2 ∞ V2.5 ƒ is linearly V dependent ƒ = α(V – V0) V0 ≈ 0.25V Pactive = αCeff V2 (V – V0) + Ileak V ∞ V3
The Case for Voltage Scaling Departing from scaling theory
The Case for Voltage Scaling Optimum VDD = 0.5v
The Case for Voltage Scaling cont… Optimum VDD = 0.5v
Enablement (1) Operating Margin improvement
Enablement (2) Low variability devices ET-SOI Fin-FET
Enablement (3) Digital Noise Resistive: dVR/VDD = IR/VDD ∞ ( VDD – VT)1.5/VDD Capacitive: dVC/VDD = [CaggVDD/(Cagg + Cvic)]/VDD = Cagg/(Cagg + Cvic) Inductive: dVL/VDD = [ L ∂I/∂t ]/VDD ∞ (L I)/(VDDҭ) ∞ (VDD – V0)( VDD – VT)1.5/VDD
Enablement (4) On-Chip Power System
Case study (IBM Blue Gene) • Top500 HPC from 2004 to 2007 • Operating at 850MHz • Performance of up to 13.9Tflop • 4096 parallel processor cores • - Three chip voltage bins
Conclusion • Power efficiency through voltage scaling. • Optimum VDD = 0.5v. • lowering of variability. • Increasing margin. • Massive parallelism. • High integration.