AOpen XC Cube EX915: 775-socket SFF barebones

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The following components were installed in the AOpen XC Cube:

  • Intel 520 processor (P4-2.8 Prescott, 1Mb cache, 800 MHz FSB in 775 casing), review loan from
  • Samsung SM-352B Combo Drive (CD-RW + DVD-ROM)
  • OCZ DDR400 512MBx2 EL DDR Platinum Dual Channel SDRAM Memory (2 sticks)
  • Samsung SP0802N - with Nidec motor. One of our favorite quiet reference drives.
  • Microsoft Windows XP Pro SP2 was installed, along with the multi-megs of updates ad nauseum.

*A note on the Intel 520 processor used for this review: Any Prescott-core P4 in a SFF PC is a challenge if you're seeking low noise as a primary goal; they run so very hot that is' hard to cool them in tight spaces without some significant airflow. Intel had announced several months ago that they were expanding the range of 775 CPUs downward to include lower clock speed Northwood P4s in the mix. We made a special request to to locate one of these for us, but they were unsuccessful. For the record, the 520 is spec'd by Intel for a Thermal Design Power of 84W (and a calculated Maximum Power of 100W), and a maximum casing temperature of 67°C.

You'll note that no video card is listed. Alas, a PCI Express VGA card was not on hand when we were doing the testing, so the integrated VGA was used. Suffice it to say that video performance can surely be made better with almost any PCIe video card, and the noise level of the system cannot be any lower than we recorded here in the absence of the extra heat a VGA card would produce. The only way the baseline noise level can be lowered is by using a quiet notebook drive, which can be as much as 5 dBA/1m quieter than the Samsung, which is one of the quietest 3.5" drive available. However, this noise reduction might well be obscured by other sources of noise in the system.

The assembly went very smoothly, with the logical open layout, and the multiple photos and step-by-step instructions provided in the manual. It was a quick and painless procedure. AOpen has to be commended for their excellent layout, cable management and friendly manual.

Socket Pin Hitch

There was one unexpected hitch, however. Jordan, SPCR's sharp-eyed lab tech, noticed that one or more of the pins on the 775 socket of the EX915 was visibly bent. It was very tough to see exactly what it was, but there was no question that some irregularities in the pattern of the pins could be seen with the naked eye. It was probably caused when I first removed the protective cover over the socket; a very small screwdriver fell into the case and may have hit the exposed pins. After some hesitation, we decided that rather than risk a CPU or motherboard failure, we'd try to straighten the pins. It was a painful half hour, but in the end, the couple of pins seem to have been straightened out.

We needed a magnifying glass at least double this size!

The system booted without any hitches after the CPU and heatsink were finally installed. We'll never know whether the system would have worked OK without our "repair" or whether it was necessary.

BIOS Flexibility

The XC Cube EX915 has a good range of user options in the the BIOS. Some of the most important ones for enthusiasts:

  • FSB: 100-400 MHz, in 1MHz increments
  • Some PCI Express VGA adjustments
  • Wide range of RAM voltage, timing and clock options

There is one glaring absence:

  • No CPU Vcore adjustment. This is important to both overclockers and silencers; the former to push the CPU a just a bit faster and the latter to make the CPU run cooler. It's an adjustment that is available in the EZ65, from 1.1V to 1.85V, which is really a good range!


This utility has appeared on many AOpen boards, and at its best, provides a huge range of extremely reliable board-level fan control that is tough to beat by any other means. In the EX915, SilentBIOS has been reduced to an automated thermal fan controller for the CPU with no user adjustments other than the CPU temperature at which an alarm sounds. There are only two settings for fan control: Full Speed or Smart Control. The latter uses its own built-in algorithm thermal to adjust fan speed in accordance with the CPU temperature reported by the sensor in the CPU socket mentioned earlier.

The AOpen Windows utility, SilentTek, is not available for the EX915. Unfortunately, the thermal reporting functions in the motherboard also seemed to be disabled except in the BIOS, which made monitoring utilities such as Motherboard Monitor useless. CPU temperature could not be monitored within Windows. The only thing we could do was to set the CPU Warning Temp in Silent BIOS to the minimum 63°C to get some idea of the thermals. At no time during testing or general use did this alarm trigger, so all we can say is that the cooling system is effective in keeping the CPU temperature under 63°C.

Why is the thermal fan controller is so crippled compared to AOpen's previous wonderfully flexible iterations?

The answer, we believe, is Prescott, the hot Intel CPU core. Safe and reliable operation are the most important goals from a manufacturer's point of view. AOpen engineers undoubtedly wanted to ensure that DIY system assembler would have adequate cooling for the Prescott. In the spring when when this system was probably being developed, early reports of the Prescott power dissipation were filtering in, and they looked scary. The most expedient way to minimize user error with a 775 CPU was to make the fan thermal controller automatic with an aggressive cooling-biased (not acoustics biased) algorithm, and not user adjustable.

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