Developers of Small Form-Factor PCs have to take special care of proper cooling. The problem of cooling is more vitally urgent in mini-systems as they use ordinary computer components dissipating quite a lot of heat packed into a smaller case. So, if the air doesn’t warm up that fast in large system cases, then in a small form-factor PC efficient cooling is much more important.
Shuttle ST61G4 uses a traditional cooling system designed on heat pipes: we have seen it in other Shuttle barebones. The 80mm fan installed on the back panel drives air through the case, and also through the thin ribs of the CPU heatsink. The heat pipes serve as a mechanism for fast heat transfer from the CPU and the heatsink, which is located at the back panel of the case, too.
So, Shuttle ST61G4 takes air in through the vent holes at the sides and front panel of the system case and exhausts it out through the back panel. Thus, the cool outside air blows around the HDD and the graphics card (if you installed it into your system). The result is quite satisfying: even the most powerful graphics cards and fast hard disk drives do not threaten to overheat inside Shuttle ST61G4.
Besides the big 80mm fan at the back panel, Shuttle ST61G4 also has two small fans. One is in the PSU, and the other is mounted on the heatsink, which is glued to the RADEON 9100 IGP chipset North Bridge. Theoretically, three fans may generate a lot of noise, which is unacceptable for a SFF PC. That’s why Shuttle equipped its barebone with a special intellectual technology intended to reduce the noise level.
The technology just drops down the rotation speed of the big 80mm fan when the system doesn’t need maximum cooling. You can configure the technology in the BIOS Setup where you choose the method for controlling the fan speed: SmartFan, Ultra-Low, Low, Mid or Full.
The algorithm is simple in Ultra-Low, Low and Mid modes: when the CPU temperature is below 80°C, the fan rotates with a fixed speed (2000, 2500 and 3000rpm). When the temperature exceeds 80°C, the fan will speed up to its full. As for the SmartFan mode, it implies step-by-step control over the fan speed: the rotation speed flexibly varies from 2000rpm to 3500rpm depending on the current CPU temperature.
This technology contributes a lot to making your system less noisy, since the 80mm fan is really loud at its full speed. Regrettably, this technology works only for the main system fan, while the two other fans are rather noisy, in spite of their smaller diameter.
Another cooling-related problem with Shuttle ST61G4 is that you don’t receive any utilities for hardware overclocking – you have to run third-party programs to track the temperatures from Windows.