Pipe that heat
Rather than stick with a low-profile heatsink/fan combo like they used for the SS50, Shuttle went with what they refer to as a "heatpipe" design for the SS40G. We can talk about such a thing conceptually all day long, but perhaps the best way to understand how it works is to just get a good look at the thing:

Looking at it from this angle, you can get a pretty good idea of how the thing works. Like most heatsinks, the "bottom" portion of the SS40G heatsink has a metal plate (copper in this case) that interfaces with the processor core and absorbs heat. However, directly above this copper plate is the copper tubing. The heat is transferred to this copper tubing and is conducted through it. The passive portion of the heatsink helps to disperse any heat that isn't absorbed by the copper tubing.

It seems that the classic definition of a heatpipe means that the tubing contains some sort of fluid that evaporates and condenses as it absorbs and releases the heat. I'm honestly not sure if this is the design used on the SS40G heatsink, or if it relies on the copper tubing itself for heat transfer.

Regardless, once the copper tubing absorbs the heat, it has to go somewhere or the tubing would very quickly heat up to the point where it was ineffective at cooling the processor. This is where the other half of the heatpipe comes in, and its purpose will become clear as soon as we look at things from a different angle:

As you might imagine, this block of fins acts as a radiator, absorbing the heat from the copper tubing and providing lots of surface area to disperse it. As you saw from the picture of the back of the cube, the fins sit right up against the vent on the back of the case. The main cooling fan is mounted on a metal shroud that goes over the fin assembly and ensures that all of the airflow produced by the fan is directed through the fins.

So how effective is this bizarre contraption? Very. One of Damage's few complaints about the SS50 was how hot it would get during operation. He noted that the top of the case would be very warm to the touch during extended periods of high CPU activity, and he was concerned enough about the heat levels inside the case to conduct tests to make sure the Pentium 4 wasn't heating up to the point of clock throttling.

When I first saw the unusual heatsink design of the SS40G, I thought it looked nifty enough, but could it handle the job? My first test for the SS40G after installing the OS was to fire up a Folding client and leave it on overnight. For those of you who aren't familiar with Folding, it's a distributed computing effort that will peg your processor at 100% utilization for hours on end. I figured that if the SS40G's heatsink solution wasn't up to the task, nothing would reveal it more quickly than an extended Folding session.

Well, as it turns out, the SS40G's heatsink not only did its job, it laughed at my pathetic efforts to overheat the system. I came in to check on the machine after a day or so of Folding hell, and the top of the box was cool to the touch. I quickly took the top off the case and touched various components with my fingers to see how hot they were. The heatsink was warm, but not so warm that I couldn't touch it for an extended period of time (I can't say the same about some active heatsinks I've used). The hard drive was also warm, but in my opinion, no more so than it would be in a full size case.

To sum up, the SS40G heatsink works fantastically well. Not only does it effectively cool a very hot processor, it does so in a way that keeps the heat from the CPU from cooking the rest of the components, and for a computer with such tight confines, that's an accomplishment that's extremely important.

Now that we've poked around the SS40G's insides, let's move on to the benchmarks.