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Thermal-Aware Reliability for Real-Time Systems (inspired by title of concurrent talk in Workshop on Low Power System on Chip -- “Reliability/Wear out-Aware Design” by Mircea Stan). Nathan Fisher Wayne State University. Reliability Model : Electromigration (EM).
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Thermal-Aware Reliability for Real-Time Systems(inspired by title of concurrent talk in Workshop on Low Power System on Chip -- “Reliability/Wear out-Aware Design” by Mircea Stan) Nathan Fisher Wayne State University
Reliability Model:Electromigration (EM) “[EM] is the aging process in metal interconnects caused by the exchange of momentum between electrons” -Z. Lu, J. Lach, M. Stan, and K. Skadron, IEEE Micro 2005 • Effect: • Atoms aggregation; • Voids form (open-circuit failure!)
Reliability Model:Electromigration (EM) • Mathematical Model of Void Growth Rate: Where s(t) – speed function; I(s,t) – current density (e.g., speed-scaled: I(t) = σs2 (t) ) kT(s,t) – thermal energy (e.g., Fourier’s Law : dT/dt = aP(t) – bT(t) ). Q – activation energy.
Lifetime Analysis:Single Processor (Interconnect) • L = lifetime of processor. • Objective: Determine a speed schedule s that maximizes Ls.t. and schedules real-time jobs {Ji = (ai, wi, di)}i where F – Void Threshold ai – Arrival Time wi– Work Requirement di -- Deadline
Issues/Questions • How is reliability-aware different than temperature-aware? • Potential Answer: It might be better to run at a higher temp for short periods of time. • Feasibility Algorithms: • Exact? • Approximation algorithms w/ ratio c that guarantee a lifetime Lopt/c? • Online Algorithms