Of course, the cooling solution is one of the most important parts of any SFF PC. First of all, because the components inside the SFF case are packed really closely to one another, which hinders proper air circulation and prevents regular coolers from doing their job well. Besides, since a SFF system looks similar to a consumer electronics device it is expected to be pretty quiet (or absolutely quiet). So as you see, designing cooling solutions for small form-factor systems is a pretty sophisticated task. Let’s find out how well Shuttle engineers managed to cope with it.
The cooling system of SN85G4 doesn’t offer anything brand new: a similar cooling solution has been used in other barebone systems by Shuttle. There is an 80mm fan with a heatsink at the rear side of the case. It blows the air inside the system case this way cooling down the heatsink, which receives the heat from the system CPU. The mechanism of heat transfer from the CPU to this heatsink is very simple and efficient: it is based on Heat Pipe technology, which we have already discussed in our Shuttle XPC Review in great detail. I will not repeat everything here, because you can always check the previous review for more details. I would like just to point out once again that Heat Pipes are considered to be one of the most efficient heat conductive solutions nowadays used for contemporary cooling systems.
The CPU cooler of SN85G4 consists of three parts: a heatsink cooled down by the airflow from the fan, a smaller heatsink with nickel-plated footing covering the CPU, and four heat pipes connecting these two heatsinks with each other. This system works in a very simple manner: when the CPU heatsink warms up, the heat pipes transfer the heat to the other heatsink, which is cooled down by the fan, so that the heat dissipates there. And that’s it.
SN85G4 uses an 80mm fan from Sunon with a variable rotation speed. Of course, the fan rotation speed is determined by the temperature inside the system case. However, the mainboard BIOS Setup allows adjusting the temperature limits, beyond which the fan rotation speed should increase. The maximum fan rotation speed is 3,700-3,800rpm and at this speed it produces quite a bit of noise. Here I have to point out it is really hard to make the fan work at the maximum of its rotation speed. But, I’d better not get too far ahead of time, this is a topic for one of our next review chapters today :)