Shuttle Zen XPC ST62K: Finally, a Quiet SFF PC!

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CPU Fan Speed Control

Like the other Shuttle XPC systems, the ST62K BIOS gives users control over the ICE exhaust fan. Since the ICE fan is the only active cooling component, controlling the fan speed will have a greater impact on overall noise than with other Shuttle systems that also feature multiple fans.

BIOS Fan Control Setting screen. Set in "Smart Fan" mode with a 60°C threshold. Note the Vcore of 1.32V. More on this later.

The BIOS offers five different fan settings to balance noise levels with processor temperatures. I used the "Smart Fan" mode with the fan threshold temperature set at 60°C. With this setting the fan will remain at its "ultra low" speed of 1900 rpm and only start ramping up if the processor temperature exceeds 60°C. During all my burn-in and benchmark testing the fan never went over this threshold.

Unfortunately I was not able to see any temperatures, voltage readings or fan speed readings while in Windows due to the lack of temperature monitoring software support for this new ATI chipset. Shuttle was not able to provide any proprietary monitoring software either which meant that I was basically in the dark, temperature-wise during all my testing with the ST62K. All I know for sure is that the CPU temperature never exceeded 60°C at a room ambient temperature of 21°C.

I tried booting immediately into the BIOS after running a CPU-intensive app to check the BIOS temperatures (which do show up, so the sensors are there, they just aren't any use with any existing Windows-based monitoring applications) but by the time the system got into the BIOS the CPU temp usually read somewhere in the low to mid 40°C range. This method is completely worthless for obtaining any accurate temperature measurements and this situation needs to be addressed. These SFF systems usually run fairly warm, and even though the ST62K is one of the best designed of any of them, the user should still be able to monitor their temperatures so they know how their system is running. It's probably even more important if one is trying to make the ST62K as quiet as possible, because the fan speed will most likely be turned down as low as possible, giving the least amount of cooling available.

Temperature concerns aside, the ICE fan is a very quiet fan at the "Ultra-Low" 1900rpm (actually about 1600rpm according to the BIOS Health Monitor screen) setting. My sample had a very slight whine and a small amount of air noise. It had no mechanical clicking noise, nor did it change speed at any time while I was using the system. The closest comparison for me is a 92mm Panaflo L1A running at about 6-7 volts. It's also not that far off from a Panaflo 80mm L1A at maybe 8~9V. The rubber-damped mount/shroud seemed to contribute no resonance or vibration noise of its own either. All told, a very quiet and effective cooling system on this ST62K. It's by far and away the quietest Shuttle XPC I've ever heard.

External Power Supply

Along with the single fan ICE cooling system, the new 180W external power supply plays a giant part in the very low noise of the ST62K. One of the biggest stumbling blocks of almost all SFF systems are noisy, actively cooled PSUs that add extra noise and heat to the case. Shuttle's ingenious solution here is to move the PSU out of the case entirely and make it passively cooled. Doing away with the typical, horrifically noisy 40mm active cooling fan on the PSU itself is another masterstroke by Shuttle. They've managed to design a passively cooled PSU that only runs slightly warm to the touch, even after extended sessions of full load benchmarking.

The PSU itself measures about 7" x 5" x 2" and is connected to the mains by a standard IEC power cord. The connection from the PSU itself to the motherboard is via a proprietary 6-pin connector. It is a univeral AC input design; it will run correctly on any voltage from 100-240VAC, 50~60 Hz. The output is +12V only, rated at 15A or 180W. Obviously, like most external power supply designs, a good portion of the functions of a standard PSU (such as splitting up the various voltage lines) have been moved on to the motherboard.

The PSU, although not small, is easy enough to stash out of the way underneath a desk or in a corner and it runs so surprisingly cool that I doubt ventilation is any concern. Set it in a corner and forget it. It makes no noise that I could hear, other than a very faint hum that's inaudible from over a foot away, and it barely gets warm even under heavy use. What a wonderful design!

Of course some people will complain that it's "only" a 180W PSU and will not be powerful enough to run a modern, high powered P4 system. To them I say "balderdash!" The lack of a AGP slot means there will be no power-hungry video cards in this system and you're limited to two hard drives and one optical drive at best so there just won't be a heavy load put on this system. My setup ran a P4 2.4C CPU, one 7200 rpm HDD and a 40x Plextor CD-RW drive. Using a Kill-a-Watt meter to measure the total current draw of this system, I got readings of 45W total while idling/surfing the web, and 103W total under full load of 2 instances of CPUBurn. 103W maximum. That still gives you a very nice cushion before you'll need to worry about running this PSU out of juice.


I chose to use the P4 2.4C CPU, 2 x 512MB of Corsair PC3200 memory and 80GB Seagate Barracuda IV hard drive from my main computer to build up this system. I did this so I could compare the performance of the IGP 9100 chipset against the 875P chipset and ATi Radeon 7500 vidoecard in my main system.

The build was super-easy and I didn't have any trouble with tight component access or anything else related to the small footprint of the ST62K chassis. Even though the 5.25" and 3.5" drive bays aren't removable, I was able to get excellent access to the CPU socket and DIMM slots by removing the slide-out hard drive tray. The CPU was easy to install, as was the ICE cooling unit. The clamp that holds the heatsink to the retention bracket is quite well designed and very easy to snap into position. The four thumbscrews that fasten the ICE fan shroud to the chassis made it a easy to bolt it into position. The two sticks of memory were a snap to install, sliding fairly easy into each DIMM slot. Many DIMM slots seem to be extra tight but the set on this Shuttle board didn't require tons of force to fully seat the RAM.

The hard drive was also easy to install. Simply bolt it into the drive tray, slide the drive tray into it's slots and tighten the whole assembly down with the handy thumbscrew. Shuttle's custom 2" long IDE cable and pre-located power connector made connecting the cables super easy. The optical drive was also very easy to mount after removing the blank face plate. The drive bolted nicely into position, and again, Shuttle's pre-located IDE and power cables made connecting it up a real breeze.

And that's it! Finished. It took longer to write that then it did to actually do it. It's the easiest system I've ever built. This "barebones" thing is pretty nice. No board to install, no I/O shield, no front connectors to puzzle out, No tiny USB 2.0 pins to fret about, no front audio connector to try and hookup to the correct headers. Literally, the most time-consuming task of the whole build was applying the thermal compound to the CPU.

Complete! Notice the lack of cable clutter. This is all thanks to Shuttle's design work.

Fired it up for the first time and dang, that ICE fan is a screamer at full rpm, which is what it does prior to being controlled by the "Smart Fan" BIOS setting. Within a few seconds after the BIOS loads, the fan speed drops to the preset rpm and the screaming stops.

I went right into the BIOS and double-checked various setting, made a few changes to thing like setting the memory timings to 2-3-3-6, verifying that the FSB was at 200MHz and Hyper-Threading was enabled. I also poked around in the Advanced Chipset screen looking at the FSB overclocking and Vcore settings. The maximum FSB adjustment is only up to 215MHz, a rather meager 7.5% overclock but that's of no particular issue to me. There is no PCI/AGP lock but that's also not an issue as 7.5% out of spec shouldn't hurt anything.

One of the coolest things I noticed was that not only was the Vcore adjustable to a relatively low maximum of 1.5875V, it was also adjustable downwards to .825V! Now this is something to get excited about! This is an eminently undervoltable board! There are very few undervoltable P4 boards, which is a shame because these CPUs will run on considerably less than default Vcore. The lower voltage you apply to the CPU, the cooler it runs. The cooler it runs, the less cooling fan you need and the cooler the case stays. Less heat is pumped into the case so you can run a slower, quieter case fan. This is all wonderful if you are trying to make your system as quiet and cool as possible. For now I left it at it's default, which for this particular CPU is 1.525V.

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