Cooling fans are an important part of thermal management for high-power chips (such as CPUs, FPGAs, and GPUs) and systems. Unfortunately, their use can sometimes raise a system's acoustic noise level to the point where it iobjectionable to the user. By measuring temperature and adjusting fan speed accordingly, the fan's speed (and noise level) can be minimized when temperature is low, but increased under worst-case conditions to prevent damage. This article describes two techniques for automatically controlling a cooling fan's speed. ……