Transiently powered computers (TPCs) form the foundation of the battery-less Internet of Things, using energy harvesting and small capacitors to power their operation. This kind of power supply is characterized by extreme variations in supply voltage, as capacitors charge when harvesting energy and discharge when computing. We experimentally find that these variations cause marked fluctuations in clock speed and power consumption . Such a deceptively minor observation is overlooked in existing literature. Systems are thus designed and parameterized in overly conservative ways, missing on a number of optimizations. We rather demonstrate that it is possible to accurately model and concretely capitalize on these fluctuations. We derive an energy model as a function of supply voltage and prove its use in two settings. First, we develop EPIC, a compile-time energy analysis tool. We use it to substitute for the constant power assumption in existing analysis techniques, giving programmers accurate information on worst-case energy consumption of programs. When using EPIC with existing TPC system support, run-time energy efficiency drastically improves, eventually leading up to a 350% speedup in the time to complete a fixed workload. Further, when using EPIC with existing debugging tools, it avoids unnecessary program changes that hurt energy efficiency. Next, we extend the MSPsim emulator and explore its use in parameterizing a different TPC system support. The improvements in energy efficiency yield up to more than 1000% time speedup to complete a fixed workload.

中文翻译：

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揭秘瞬态供电计算机的能耗动态

瞬态供电计算机 (TPC) 构成了无电池物联网的基础，使用能量收集和小型电容器为其运行供电。这种电源的特点是电源电压变化很大，因为电容器在收集能量时充电，在计算时放电。我们通过实验发现这些变化会导致显着的波动时钟速度和能量消耗. 这种看似微不足道的观察在现有文献中被忽视了。因此，系统的设计和参数化方式过于保守，缺少许多优化。我们宁愿证明有可能的准确地建模并具体利用这些波动。我们推导出作为电源电压函数的能量模型，并证明了它在两种设置中的用途。首先，我们开发了 EPIC，一种编译时能量分析工具。我们用它来代替现有分析技术中的恒定功率假设，为程序员提供有关程序最坏情况能耗的准确信息。将 EPIC 与现有的 TPC 系统支持一起使用时，运行时能效显着提高，最终导致完成固定工作负载的时间提高 350%。此外，在将 EPIC 与现有调试工具一起使用时，它可以避免不必要的程序更改，这些更改会损害能源效率。接下来，我们扩展 MSPsim 仿真器并探索它在参数化不同的 TPC 系统支持中的用途。