I got a nice new NUC6i5SYH and have noticed erratic fan control behavior. The first thing I did before setting up the OS was update to BIOS 033, so I already have the latest version. I usually use Arch Linux (currently kernel 4.3.3), but also have a Windows 10 partition for gaming. I noticed that sometimes after power on or reboot (i.e. during BIOS initialization) the fan would stop completely and would remain in that state, no matter what happens to the temperatures. This is very dangerous as the CPU (and memory, PCH, mainboard) gets extremely hot. I only noticed this because I started a game and the game suddenly was very sluggish. This means thermal protection kicked in and throttled the CPU. I then noticed the fan was not moving at all. A reboot brought it back and because of the high temperatures it started with a very high RPM and noise. After that I noticed it several times already. This happens sometimes after reboot or after powering on from S5 and already happens during BIOS initialization, i.e. even if stuck in the grub boot menu (e.g.) the fan is not running at all (even though minimum duty cycle is configured to 35%).
At one other time (so far) the fan was initialized to a very high (max?) speed during BIOS initialization following a reboot and remained there until the next reboot.
Also, why does the firmware not notice that the fan is not moving at all and display warnings, beeps etc.? Why isn't there at least a thermal shutdown initiated once the CPU reached Tjunction (which it did!)?
Finally, I hope that these fanless episodes didn't harm the board or CPU. PCH, memory, CPU all got extremely hot (CPU > 100C, memory >70C).
Note that the fan never stopped (if it was running initially) once the OS was booted. So this seems to be an error in fan control initialization during POST. If this is done correctly, the fan behaves normal during the whole OS usage. But if it fails, the fan runs either at some very high (max?) speed or not at all, independent of any temperature readings and does not return to normal operation until the next boot.