This is the CPU fan controller. This is pretty essential because the fan is as noisy as usual at full speed (the default out of the box) and this features slows it down to the minimum necessary for a cool CPU. It's then pretty quiet. It blows directly outside the case through holes in the case, avoiding heating the inside of the case, which probably allows for the quiet PSU fan. Good news: this is a hardware or BIOS controlled feature, so once enabled in the BIOS it works fine with Linux.