用于间歇计算系统计时的磁性隧道结
Magnetic Tunnel Junctions for Timekeeping in Intermittent Computing Systems
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中文总结 AI 辅助
研究针对无电池间歇系统停电擦除计时状态的问题，提出FLINT计时装置，利用“损坏”MTJ阵列随机保留损耗读取时间，经验证和模拟，该装置能耗低、面积小、误差小且调度错误少。
中文摘要 AI 辅助
无电池间歇系统可无人值守运行数年，但停电会擦除计时状态，影响传感、调度和协调。现有计时装置通过电容器放电推断经过时间，存在诸多问题。我们提出了FLINT计时装置，它通过“损坏”的磁性隧道结（MTJ）阵列的随机保留损耗读取经过时间。其衰减时间尺度由器件几何结构固定，读取能量与测量间隔无关且不随器件老化漂移。我们针对21个制造的MTJ验证了FLINT的阵列模型，在实际设备跟踪驱动模拟中评估了完整计时装置，结果表明它在10%误差内跟踪超过15分钟的停机时间，能耗仅1.03μJ，占用面积不到0.1mm²，在一年部署中比老化电容器时钟产生的调度错误少16 - 52倍。
英文摘要
Batteryless intermittent systems run unattended for years, but power failures erase timekeeping state, corrupting sensing, scheduling, and coordination. State-of-the-art timekeepers infer elapsed time from capacitor discharge; however, the capacitor must be sized for the longest interval measured (so range, energy, and area grow together), and repeated charge-discharge cycling lowers capacitance over time, biasing every estimate further as the deployment ages. We present FLINT, a timekeeper that reads elapsed time from the stochastic retention loss of an array of "broken" Magnetic Tunnel Junctions (MTJs)---spintronic memory cells engineered to lose state predictably. Because the decay timescale is fixed by device geometry, the energy to read it is independent of the interval measured and does not drift with device age. We validate FLINT's array model against 21 fabricated MTJs, then evaluate the full timekeeper in real-device-trace-driven simulation, showing that it tracks over 15 minutes of off-time within 10% error while consuming only 1.03 $μJ$ and occupying under 0.1 $mm^2$---$9.2\times$ the range at $11\times$ lower energy than prior work. It extends to longer intervals at no added cost, and makes $16-52\times$ fewer scheduling errors than an aging capacitor clock over a one-year deployment.
