I did some more experimenting with this tonight and it turns out my choice of fans is pretty sub optimal. The principle cause of noise in this system in the CPU cooler and case fan. Getting these fans to run slower when they’re not needed is the key to making the system quieter.
Fan configuration rethink
Turns out the CPU cooler is a three pin not a four pin cooler. I picked this particular cooler because I was concerned about the amount of space in the AeroCool’s two layer case design. The case actually has about 11cm of clearance which would have been enough for a four pin PWM cooler like the Arctic Cooling Alpine 64 PWM which is 9cm high and uses a larger quieter fan and is four pin PWM compatible. The 12cm fan I bought for the front of the case is odd in that it only blows outward and isn’t reversible (a feature of some Arctic Cooling fans). Cases are designed to flow air front to back and this is a rear case fan (blowing outwards) although the documentation doesn’t mention this.
While this is a tad annoying I’m not overly concerned about air flow given the low power consumption and heat output of the system cooling isn’t an issue. If you decide to build your own you might want to rethink the fans somewhat and get two PWM compatible fans for the CPU and a 12cm fan that’s designed for the front of the case so air flows front to back.
Optimizing the existing fans
However, all is not lost. Some further messing about with the BIOS and fans configuration has resulting in a much quieter system. So quiet in fact that I had to double check that the fans were running at all.
I’ve changed the fan configuration and now have the fans daisy chained off the CPU FAN connector and nothing connected to SYS FAN. The final connector from the fans goes to the front of the case. The next step is to reconfigure the BIOS to run the fans as slow as reasonable possible.
To setup the BIOS make sure that the smart fan option is enabled and then set the smart fan options. Because there are a mixture of three and four pin fans I ended up going with the 3-pin setting in the BIOS and after running the calibration I tweaked the values somewhat (see picture). The end result is a slow running CPU fan and a case fan that is actually off when the case is cool and kicks in if and when things heat up. Just to make sure I had things covered I also set the shutdown temperature option to 60C/ 140F. If the CPU core starts to overheat even slightly the server will shut down.
I tested this by running some CPU performance benchmarks and heating up the case by placing a hair dryer next to the case’s rear vents. Sure enough as the temperatures rise the CPU fan speeds up and the case fan kicks in. For the most part though the server is next to silent as the CPU fan isn’t running at high speed.
These settings will vary depending on your exact system configuration and the ambient temperature and airflow within the room. You may need to modify the settings given here to get the right behavior.