Performing a 'make -j 5 buildkernel' with the cooling fan on and off on a GPD MicroPC.
With the fan on and hw.acpi.thermal.tz0._PSV=90C, a build takes 18:16. With
the fan off, passive cooling works well, the target temperature is not
exceeded, and the CPU frequencies are seen to drop as needed. However, the
build takes 25:51.