Cooling System

The most interesting technological solution in the barebones from Shuttle is the cooling system, of course. The small size of a SFF PC does not allow putting several fans into it. That's why most manufacturers try to do with one fan only. Moreover, with a not very fast one, so that the system could be quiet.

Both reviewed XPC from Shuttle follow this design. They both have only one 80mm fan mounted at the inside of the case back panel. This fan blows the air throughout the entire case and also takes heat off the CPU. Under the fan there is an additional heatsink that receives heat from the CPU. The heat comes to this heatsink in a simple and effective way: the Shuttle system uses heat pipes technology.

In order to understand the way the CPU is cooled in this system, let's get acquainted with the construction of the CPU cooler that was created with the help of I.C.E. (Integrated Cooling Engine) brand name technology.

Cooler from Shuttle SK41G (left); Cooler from Shuttle SB51G (right)

The CPU cooler itself consists of three parts: the heatsink, through which the fan blows the air, a small heatsink with aluminum or copper sole mounted right onto the CPU and four heat-conducting pipes that connect the heatsinks. The system works this way: after the heatsink mounted on the CPU is heated up, the heat is taken via the pipes to the first heatsink. The hot air is blown off it by the fan. This rather simple description conceals a witty technology of heat-conducting pipes functioning.

George Grover, an engineer, invented the first heat-conducting pipe as we know it in 1963, although the concept was borrowed from contraptions used by English bakers for over a hundred years. The heat-conducting pipe is a soldered-up pipe with some liquid inside: actuating fluid. For example, the pipes used in Shuttle I.C.E. are filled with a solution, 95% of which is water. The pressure inside the pipe is much lower than the atmospheric pressure, so that the boiling-point of the liquid is about 30-35^oC. After the "hot" end of the pipe, which is built into the CPU heatsink, is heated to this temperature, the water inside the pipe begins to boil and the hot vapor ascends up the pipe. Here it meets the upper heatsink, cools down and gets condensed. The condensate drops down onto the pipe walls and flows down to repeat the cycle once again. So it becomes possible to effectively transfer heat from the CPU to a remote heatsink. For example, some estimates show that heat-conducting pipes are twice as effective as an ordinary copper shaft. Thanks to that, the CPUs feel all right in Shuttle XPC systems, although there is just a small heatsink without any fan over it.

One more thing to mention is that the company equips Shuttle SK41G and SB51G with fans changing their rotation speed depending on the temperature. This helps to reduce the noise. Thus, the fan in Shuttle SB51G can rotate in three different speeds depending on the current CPU temperature. In the "noiseless" mode, the cooler rotation speed is 2000rpm, in the "normal" mode - 3000rpm. If the CPU temperature is above 80^oC, the fan rotation speed reaches 3500rpm.

Shuttle SK41G can boast a similar system. But since the external thermal diode is less accurate, the critical value is lowered to 65^oC. If this value is reached, the fan speeds up to 4500rpm. We should acknowledge that at regular work the XPC from Shuttle does produce less noise than ordinary cases. But this holds true only until the cooler switches to the "fail-safe" mode. After the rotation speed grows up to 3500rpm or 4500 rpm, the noise produced is not that low. Fortunately, the fan in XPC rarely works in this mode.

The cooler in Shuttle SK41G has no copper sole, although AMD recommends using it in cooling systems for new Thoroughbred based processors. This shouldn't be considered a drawback as Shuttle engineers took another material instead of copper with no worse thermal conduction. As for the cooling system of the other XPC, the CPU cooler for Pentium 4 has a copper sole.

Cooler from Shuttle SK41G (left); Cooler from Shuttle SB51G (right)

Both coolers (for Pentium 4 and Athlon XP) boast a very smart fastening mechanism. The SB51G cooler is pressed to the CPU with a smart latch, and in SK41G the cooler is fastened with four spring screws. The Shuttle SK41G package also includes a copper shim laid onto the CPU, preventing the cooler from leaning sideward, so that it could be mounted straight without damaging the processor surface.

Other Components and Assembly

As we have said, in order to transform the barebone from Shuttle into a fully-fledged computer, you will need to install a CPU and memory and to connect drives. Some users might also want to connect an external graphics card and an expansion card. Luckily, Shuttle engineers kept this in mind when designing their systems, so that all these operations will not require too much effort from you.

The barebones come with a detailed assembly manual, while the inner component layout is very smart. It's nice that Shuttle even thought about the best way to locate the cables inside the case, and enclosed ties, double-side scotch and special clips.

The installation of hard disk drives, floppy drives and optical drives doesn't arouse any problems: the special bay can be detached easily. After that, you can access all the mainboard components to install the CPU and memory modules.

The expansion cards, including the AGP graphics card, are installed after the drives bays are back in their places. Note that these small "cobes" can accommodate not only small graphics cards, but also massive ones like NVIDIA GeForce4 Ti4600. The only cards that won't fit into Shuttle SK41G and SB51G are GeForceFX based ones and cards with massive cooling systems like ABIT OTES (see our article called "Overclocker's Dream: ABIT OTES Review") as they require additional space around the card.

The only tool you will need during the Shuttle barebone assembly is a brace screwdriver for detaching the drives bay and mounting the drives into it. The case cover and cooling system can be removed without any tools as they have very easy to undo screws.

To illustrate the above-described procedure, let's go through Shuttle SB51G assembly step by step:

• Remove the case cover;
  
  
• Remove the drives bay;
  
  
• Remove the cooling system;
  
  
• Install the memory and CPU;
  
  
• Mount the cooling system;
  
  
• Mount the hard drives and install the drives bay back into the case;
  
  
• Install the graphics card;
  
  
• Assemble the case.

As you see, all is nice and simple. The only strange thing is that Shuttle didn't use round IDE and FDD cables that could come in handy in small cases like that thanks to their better aerodynamic characteristics. Shuttle offers two flat cables instead and one flat cable cut into stripes, which are gathered in a bunch.

Thermal Conditions

Now, we are passing to practical tests of the XPC from Shuttle. The first issue we want to check is the temperature mode of both systems. Although the manufacturer claims that the cooling system used is very effective, we still doubt that one low-speed fan can cool very fast processors inside such a small case.

First of all, we should point out that our powerful system built inside a Shuttle barebone solution will include two components generating a lot of heat: the CPU and the graphics card.

As for the graphics cards, they can be cooled rather easily, which our tests confirmed. The thing is that beside the AGP slot there are holes in the case. The cool air from outside gets sucked through the holes and is then blown away by the cooler. This is enough for the graphics card to work stable. We checked it with both: ATI RADEON 9700 PRO and NVIDIA GeForce4 Ti4600. Both cards did well inside the XPCs, no problems occurred.

As for the CPUs, we revealed certain problems dealing with insufficient cooling. The first to undertake our tests was Shuttle SK41G for AMD CPUs. As this XPC doesn't support 333MHz system bus, the top model that can be used in this system is AMD Athlon 2600+. So we installed this CPU into Shuttle SK41G and got the following results:

As the tests showed, the temperature remained acceptable in all the modes. The CPU operation doesn't deserve any reproach. We should note, though, that when a graphics card was installed, the cooler in Shuttle SK41G sometimes switched to the "fail-safe" mode, speeding up to 4500rpm. In this mode Shuttle SK41G proved a rather noisy system. Nevertheless, Shuttle SK41G copes with the cooling all right even when the "hottest" components possible are installed.

Next, the same tests were run with SB51G. This XPC supports processors from the Pentium 4 and Celeron families and, as the manufacturer claims, can work with the most powerful Pentium 4 CPUs with Hyper-Threading technology.

However, it was not all that well in practice. After we installed a Pentium 4 3.06GHz processor, the cooling system proved too weak for it. No wonder: when releasing its new processors, Intel toughened the cooling systems requirements for its CPUs. When Pentium 4 3.06GHz is used, the temperature in the case goes up to 50-55^oC, so it's quite natural that this warm air cannot properly cool a fast processor like that. Athlon XP is very easy to deal with in this respect, as it can function at higher temperatures than Pentium 4 processors. So, Shuttle SB51G couldn't work stable with the most powerful Pentium 4 processor available today.

Then we checked how the things stood with a less "warm" CPU. It was Pentium 4 working at 2.53GHz. The heat dissipation of this CPU is lower and it doesn't require anything specific from the cooling system. As a result, the system worked absolutely stable. Here are the temperature data for Shuttle SB51G with a Pentium 4 2.53GHz processor:

As Pentium 4 dissipates more heat than Athlon XP, the internal temperature of Shuttle SB51G turned to be a little higher. But in the "idle" mode Pentium 4 is cooler thanks to the Halt command that brings the CPU to a full stop. The i845GE chipset also seems to contribute to the inner temperature a lot, as it seems to be heating much more than VIA KM266 used in Shuttle SK41G.

So, we may say that Shuttle SB51G cannot work with the top-end model of the Pentium 4 family because of the not very efficient cooling system. At the same time, Pentium 4 CPUs working at about 2.53GHz are quite stable in this XPC.

Performance

Next thing we did was checking the performance of the systems assembled in the barebones from Shuttle. We benchmarked the systems with both: integrated graphics core and an external ATI RADEON 9700 PRO graphics card. The testbed configurations looked as follows:

The benchmarks were run in Windows XP Professional operation system. The BIOS Setup settings of both systems were adjusted so that we could get the maximum performance.

We obtained the following results:

There are a few points that are worth mentioning. First, it's quite clear that Intel Extreme Graphics integrated core is much faster than ProSavage8 from VIA-S3. In fact, the integrated graphics core by Shuttle SK41G can only provide comfortable work in 2D office applications. The results ProSavage8 shows in 3D are simply catastrophic. Meanwhile, Intel Extreme Graphics can show an acceptable fps-rate in some games. New games, like Unreal Tournament 2003, load the graphics core so heavily, though, that even the Intel's graphics cannot cope with it. So, gamers shouldn't rely on the integrated graphics.

Moreover, ProSavage8 has some problems with 2D, too. In the 1024x768 resolution, there appears some evident "fuzziness" of the picture. The 2D however, appears to be no problem for the Intel Extreme Graphics.

After we installed a fully-fledged graphics card, the performance of the both XPCs rose up to an acceptable level even in games. Overall, Shuttle SB51G shows better results due to faster memory subsystem as well as faster system bus of the Pentium 4 processor family.

As for applications which need a lot of computing power, Shuttle SK41G wins them all with Athlon XP 2600+ having higher "pure" performance than Pentium 4 2.53GHz.

On the whole, we should admit that the small "cubes" from Shuttle are not a kid's toy. These small-size and elegant XPCs can brow into serious competitors to big and noisy desktop PCs from the performance point of view.

Conclusion

Today we have discussed two quite excellent products from Shuttle. This company succeeded in demonstrating that the big and clumsy cases used in modern PCs are not a vitally necessary thing. High-performance computers can live in small cases of original design, too. That's the main outcome of this review.

As for the reviewed products in particular, we should note that Athlon XP processors are better fit for Small Form Factor PCs, however strange it may seem. Lower performance of solutions based on these CPUs can be explained by the absence of good integrated chipsets for them. That's why we are looking forward to meeting an XPC from Shuttle based on the NVIDIA nForce2 IGP, SN41G, showcased by the company at the last Comdex Fall:

To wind up the review, let's list all the advantages and drawbacks of Shuttle SK41G and Shuttle SB51G:

First comes Shuttle SK41G.

Highs:

• Outstanding design, small size, aluminum case;
• Easy assembly;
• High functionality;
• Outstanding and efficient cooling solution.

Lows:

• Low performance integrated graphics;
• No support for 333MHz bus and DDR333 SDRAM;
• No DVI-Out.

Now the highs and lows for the Shuttle SB51G.

Highs:

• Outstanding design, small size, aluminum case;
• Low noise level;
• Easy assembly;
• High functionality;
• Relatively fast integrated graphics.

Lows:

• Insufficient cooling for the fastest Pentium 4 processors.