Elevated on-chip temperatures significantly degrade performance, energy-efficiency, and lifetime of processors. The cooling system for a chip is typically designed to remove the worst-case heat generated per unit area. Cooling demand, however, spatially and temporally varies across a chip as hot spots occur on different locations with different intensities. Thus, designing a homogeneous cooling system for a chip can be inefficient. Recently, hybrid cooling strategies, such as integrating thermoelectric coolers (TECs) with microchannel liquid cooling, have been explored for hot spot mitigation. The efficiency of such a cooling system strongly depends on the operating point of each cooling method, as well as the locations and intensities of the hot spots. To this end, we first devise a compact thermal modeling method for the design and evaluation of hybrid cooling systems in a fast and accurate way. The proposed model provides up to four orders of magnitude speedup in simulation time compared to COMSOL multiphysics simulations with less than 2.9 °C average temperature error. Leveraging our fast model, we develop LoCool, a hybrid cooling optimization method, which jointly determines the most energy-efficient cooling settings for a given chip power distribution and temperature constraint. LoCool determines the liquid flow rate and the input current for each TEC depending on the cooling requirements for individual hot spots as well as for the background heat. Experimental evaluation shows up to 40% cooling energy savings compared to designing homogeneous cooling systems under the same thermal constraints.

中文翻译：

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LoCool：在本地对抗热点以提高系统能效

升高的片上温度会显着降低处理器的性能、能效和使用寿命。芯片的冷却系统通常旨在消除单位面积产生的最坏情况下的热量。然而，由于热点出现在不同位置且强度不同，因此芯片上的冷却需求会在空间和时间上发生变化。因此，为芯片设计均匀的冷却系统可能效率低下。最近，已经探索了混合冷却策略，例如将热电冷却器 (TEC) 与微通道液体冷却集成在一起，以减轻热点。这种冷却系统的效率在很大程度上取决于每种冷却方法的工作点，以及热点的位置和强度。为此，我们首先设计了一种紧凑的热建模方法，用于以快速准确的方式设计和评估混合冷却系统。与 COMSOL 多物理场仿真相比，所提出的模型在仿真时间方面提供了多达四个数量级的加速，平均温度误差小于 2.9 °C。利用我们的快速模型，我们开发了 LoCool，这是一种混合冷却优化方法，可针对给定的芯片功率分布和温度限制共同确定最节能的冷却设置。LoCool 根据各个热点和背景热量的冷却要求确定每个 TEC 的液体流速和输入电流。实验评估表明，与在相同热约束下设计均质冷却系统相比，冷却能量节省高达 40%。