Premise that the Udoox86 Ultra board's architecture limits heat production and the large heat sink supplied is cooling properly I have to say that UdooX86 official fan is really excellent because it has a low noise in decibels and a very intelligent BIOS management. During normal activity I have a 42 to 57 degree Celsius. I have copied 97 GB of data from a SSD SATA connected to the USB 3.0 port to the internal SSD M2 and the temperature ha gone up to 80° C (according to applet of Debian 9 Strecth, a plugin of xfce4). At this temperature, the fan has switched on for ONLY 5 or 7 seconds and then reactivated some time later. In this way the fan was very discreet. The fan was able to avoid the block of the UdooX86 for overheating without to annoy for the noise. The buzzing of my old notebook fan gave me a great deal of annoyance, indeed I have to say that this fan is very nice to me.
