AOpen XC Cube EX915: 775-socket SFF barebones

Table of Contents

The EX915 is a 775 or socket T SFF barebones from AOpen, based on the same mechanical platform as the previously reviewed EZ65, but with a more techno sleek facia and the Intel 915 chipset. Socket 775 processors appear to be all Prescott-core right now. The $6 million question: Can a Prescott-CPU SFF system be quiet?

Dec 1, 2004 by Mike Chin with Jordan Menu in the lab

AOpen XC Cube EX915
Selling Price
Jordan Menu has been helping out in the SPCR lab for the last couple of months with equipment testing and various ongoing projects. In his final year at Langara College in Vancouver, Jordan is self taught with computers, having built about 20 machines for family and friends. He provide tech support for a couple of businesses as well. Jordan loves case and system modding and has modded his personal computer to near inaudible levels.

– Mike Chin, Editor / Publisher, SPCR

Like AMD’s socket A, the Intel socket 478 will soon become history, to be displaced by the socket LGA775 (also called socket T). Everyone knows by now that the new Intel socket reverses the placement of the contact pins between CPU and motherboard. Historically, they have always belonged on the CPU. With socket T, the pins have been moved to the motherboard and the CPU now sports rows of tiny round flat copper contacts.

Pins turned into buttons on the CPU…

…and pins sprouted in the motherboard socket.

Intel cites many positive reasons for the change, the most important of these being the number of CPU failures and returns directly attributable to damaged pins. They claim the new system will dramatically reduce the number of such returns. To ensure success, Intel has even produced a downloadable video to show you how to install a 775 processor. Whether the motherboard makers experience an increase in returns due to damaged pins on the boards is a question that can only be answered in time.

Socket T boards and barebones systems have been in production since midyear. Our first close look at one is the XC Cube EX915, AOpen‘s first 915 chipset 775-socket Small Form Factor (SFF) barebones PC. As with the XC Cube EZ65 we previously reviewed, it’s an attractive package, small to average size for a SFF PC, packed with many features.

The cosmetics are bolder than the pearly white of our EZ65 review sample, but still understated and elegant. It is all sleek techno sliver and black, with a unique, curved fine-perforated silver facia. Visual appeal is always personal; I find it quite attractive.

Despite the change in chipsets from 865 to 915 between the EZ65 and the EX915, the basic chassis remains the same. The dimensions and the layout are very similar, and some of the same components are used, notably the power supply. This is a good thing. It’s a nice compact frame with proportions that are pleasant to the eye and acoustics that, in the EZ65, are very good for a SFF.

One very good reason for the similarity in case and internal layout is that AOpen does a mix and match of technology and style. They have four case designs, all with the same dimensions. The location and size of the side vents appear to be similar but perhaps not identical; they may vary with the motherboard.

AOpen’s XC Cube “Body” Lineup

There are several platforms to choose from. The differences between some of them are subtle. You will want to check AOpen’s XC Cube product pages for full details.

Code #
CPU socket
Intel 915G / ICH6
Socket T LGA775
SiS661FX / SiS964
Socket 478
SiS661FX / SiS964L
Socket 478
Intel 865G / ICH5
Socket 478
Intel 865PE / ICH5
Socket 478
Intel 865G / ICH5
Socket 478
nForce2-GT / MCP-T
Socket A

As with most SFF barebones systems, the AOpen EX915 comes in a handy colorful box that’s easy for you to carry away from the store. It contains two small boxes containing no fewer than three different kinds of AC cords (for different countries), colorful manuals and quick guides in multiple languages, as well as the usual software and driver CDs. It really is quite user friendly so that even a novice should feel comfortable assemble a system with this barebones. Considering Shuttle’s comment in our recent interview that only 1-2% of the PC market are capable or interested in assembling their own PCs, all this user friendliness is probably very important.

Obligatory handy retail box.

Parts and instructions in enough languages to conquer the consequences of the Tower of Babel.


AOpen cites the following specifications for the EX915.


Size WDH(mm)

Same as EZ65


Intel 915G / ICH6


Socket T

Intel GMA 900


PCI slot

PCI Express x16


AC97 5.1CH


ATA Connector
Limitation of chipset

SATA Connector

Part of chipset. 4 seems overkill for a SFF

USB 2.0
2(Rear) /
2(Front) / 4(Internal)
very complete

1(Rear) /
2(Front) (6/4pins)
very complete

Drive bays

Power Supply
275W (w/8cmFAN)
275W is pretty big for SFF

The chipset is said to be the Intel 915G, but it is likely to be the 915GV, which included the Intel GMA 900 integrated video. This is one of several differences from the AOpen EZ65, which featured the Intel Extreme Graphics 2 integrated video. On paper, GMA 900 is a big improvement over the IEG2 video. This newer GMA 900 is still not quite the equal of integrated VGA in nVidia2 or ATI 9100 chipsets, however. (See this Hardware Central article for a more detailed discussion of GMA 900.)

Still on the topic of video cards, there is no AGP slot; the 915 chipset incorporates the PCI Express X16 video slot.

The power supply looks the same as the one in the EZ65, but it is rated at 275W, considerably more than the 220W of the EZ65. This is in anticipation of higher power demand from P4 Prescott core CPUs in LGA775.

With the EZ65, AOpen had a document that specified noise at idle with a “typical configuration” to be 28.4 dBA in the Operator Position as defined by ISO 9296 (mic place about 60 cm from the front). I could find no acoustic specifications for the EX915.

Other features:

  • EzWinFlash allows BIOS updates in Windows for simplicity and convenience.
  • JukeBox turns the XC Cube into a full-function CD player that turns on almost instantly because the software loads before Windows, just past the boot.


The front bezel is a perforated sheet of aluminum with black plastic insets. When the power is on, a blue light comes on around the large black power button, below which is another blue LED for HDD activity. The optical drive hides behind the spring loaded hinged door which gets pushed open by the drive tray. The external 3.5″ bay can be filled with either a floppy drive, or more likely these days, a multi-memory card reader. Get one that’s black and you’ll retain the cool look. The one-piece U-shaped cover appears to be anodized aluminum.

In the bottom front panel oval recess are an optical S/PDIF connector, audio in/out, two USB 2.0, and IEEE1394 6-pin and 4-pin ports. A very comprehensive front I/O panel, indeed.

Note how the vent on the left side is large than…

…the vent on the right side.

The vent on the left side acts as an intake for the entire system, including the video card, CPU and PSU. The right vent is mainly for the exhaust from the CPU fan. The remainder of the heat is intended to exhaust through the PSU.

The back panel is clean and tidy, like the front. There are connections for mouse, keyboard, monitor, parallel printer and COM1, a coax out RCA port, IEEE 1394 port, S/PDIF output, two USB 2.0 ports, Ethernet LAN (RJ-45), and three audio jacks: line-in, speakers and mic. The power supply is the same custom size and shape as used on the EZ65: A thin 80mm exhaust fan, a 115/230VAC switch, on/off power, and the IEC AC jack. The grill doesn’t look too restrictive. Covers for PCIe slots are on one side.

Four nice feet with soft rubber centers are located at the corners of the bottom. They are soft enough to help minimize vibration transfer from the XC Cube into whatever structure it is placed on. There are no vent openings in the bottom of the case.


The interior is just like that in the EZ65: Neat, tidy and well laid out. Extensive cable management with plastic zap straps and cable sleeving routed along the metal channels keeps clutter to a minimum. The removable drive cage makes it especially handy to get access to everything directly.

Tidy layout and great cable management for ease of installation.

As in most SFF systems, the PCI slot is closest to the CPU and the PCIe video card slot is closest to the edge of the board. There is a simple physical reason for this arrangement: It’s only on the edge that any of the larger AGP boards can be physically accommodated, due to space restrictions. The drives in front get in the way otherwise. This location also allows more direct access to outside air for GPU cooling.

PCIe video card slot is closest to the edge of the board.

The first step is to remove the drive cage assembly by undoing two screws, slipping it back, then lifting it off. Much of the board is then completely accessible. Note that there is only one parallel IDE connector, which is apparently dictated by the 915 chipset.

Removing the drive cage gives access for CPU, heatsink and memory installation.

Another view without drive cage.

The drive cage holds all the drives. Ideally the drives should be installed in the cage, and then the populated cage mounted in the case. The external 5.25″ and 3.5″ drives should not be screwed tight so that you can get the alignment just right before doing so.

Cage for all the drives. A thumbscrew allows removal of the bottom sideways HDD even after installation in the case.


It was a bit of a surprise to see a socket 478 heatsink retention frame around the 775 CPU socket. But it makes sense: For an integrated barebones system, the manufacturer can customize as necessary to make things work, without worrying about universal case form factors.

Socket 478 heatsink retention frame around the 775 CPU socket.

A geek’s idea of good marketing? HS on the SB chip is an AOpen logo.

A close look at the center of the CPU socket shows the same type of thin-film temperature sensor found also in the EZ65. This sensor is used for the thermal feedback loop of the AOpen SilentBIOS fan control system.

The supplied integrated heatsink / fan is all copper, and incorporates both heatpipes and a duct or shroud. A 70 x 15mm fan is used . The base is flat and smooth, though slight machining marks can be felt. The steel spring clips are standard socket 478 fare: Pretty easy to use and quite secure. As in the EZ65, the fan is set up so that it blows across and through the fins horizontally.

Ends of the two heatpipes visible at the top.

Base is smooth enough.

Fan blades visible on other side through spacing in the fins, along with the heatpipes.

The HSF is installed with the fan on the left side of the case blowing towards the right. Some benefits from this side-to-side airflow arrangement:

  • Low back pressure to the fan compared to the conventional blow-from-top setup. This reduces turbulence noise.
  • Hot air from the CPU/HS is directed out of the case through the right side vent instead of using another fan to do that job.

These thermal airflow simulations for the EZ65 are still relevant here.

Outside air is drawn in through the large openings on the left near the front.
It flows across the drives, providing cooling, before being pulled into the PSU and the CPU cooler.

The CPU fan blows the air through the heatsink fins and directly out the right side vent on the other side.

The power supply is NOT a standard ATX design. It’s smaller in every way, maybe a little bigger than 1/3 the size of standard ATX PSU. It uses an 80x20mm fan whose speed is thermally controlled. This is better than the smaller fans often used in SFF systems, because 80mm is about the smallest diameter fan that can push a decent volume of air without having to spin too fast. A label on the PSU provides the following specs:

AC Input
115 / 230 VAC, 50-60 Hz
DC Output
Current (A)
Max Power
Total Power

Surprisingly, it offers dual 12V lines! Note that the current for the individual voltage lines have almost no bearing on the total output power. For example, the max output for the individual +5V and +3.3 lines (56.1W and 90W), far exceed the max power available for the combination of the two lines. The PSU is equipped with passive power factor correction.


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.


A. Performance

Benchmark tests were performed using the most recent version of Sisoft SANDRA: 2005 Lite. The raw numbers are not directly comparable to results from earlier system tests.

The score here is directly related to clock speed and falls pretty much as expected.

The dual channel memory falls right in line with the reference data in the SANDRA
Interestingly, the reference data on the older 865PR chipset
is better than the newer 915.

The current Futuremark video benchmark is 3DMark03, but the older 3DMark2001 (v330) was used because it is the one we used in a handful of SFF system reviews already. The 5359 score is double that achieved by the AOpen EZ65 with its Intel Extreme Graphics integrated video, and just a hair higher than the 5336 score of the ATI IGP 9100 video processor.

B. Power and Acoustics

The total AC power draw was measured using a Seasonic Power Angel AC power meter. The ambient temperature was 21°C during testing. SilentBIOS was set to Smart Control. No internal system temperatures are reported because the board sensors are not accessible as reported earlier. We do know that the CPU temperature remained below 63°C at all times.

AC Power
HDD Temp
Idle in Windows XP
30 dBA@1m
Idle, HDD suspended
28.5 dBA@1m
Full Load: CPUBurn
35 dBA@1m
* Sound Pressure Level measured 1 meter from front panel in 20 dBA ambient room.
The ISO 7779 “Seated Operator Position” SPL puts the mic 0.5m in front of and 0.45m above the table top. For the above system, this SPL measurement is 3 dBA higher — 33 and 38 dBA/1m

The AOpen EX915 at idle in this configuration was fairly quiet, but slightly noisier than the similarly configured EZ65 we tested. The main sources of noise appeared to be hard drive and CPU fan related. The CPU heatsink fan spins faster than in the EZ65. The reason for this difference is twofold:

1) The fan speed is thermally controlled by the Smart Control of SilentBIOS rather fixed at 50% as it was in the review of the EZ65. It appears to be the same fan, of reasonable quality and decent acoustics at lower speed but not exactly quiet at the near 5000 RPM maximum.

2) The Intel 520 CPU runs much hotter than either the P4-2.53 or P4-2.8 used for the AOpen EZ65 review. The thermal fan controller keeps the fan spinning a bit faster even at idle.

The effect of hard drive vibrations on the overall acoustic could be easily heard. Panel resonance contributed significantly to the sound, and even clamping the whole system by grasping it firmly with both hands from the sides did not eliminate the aluminum hum. This is a common problem with almost all aluminum cases; the 1/3 density of aluminum compared to steel makes it resonate easily in sympathy with vibrations from the moving parts in a PC — fans and drives.

Because the Smart Control fan controller is quite sensitive to CPU load, the CPU fan speed varies audibly as different programs and applications are accessed and used. The variability of the noise can be quite annoying, especially as the fan reaches high speed and different parts of the case vibrate and emit different kinds of noises.

A quick and dirty temporary elastic cord suspension of the hard drive was implemented to see how much of an effect the hard drive vibrations had on this setup. The overall noise dropped only about 1.5 dBA to 28.5 dBA @ 1m but the improvement was subjectively much more significant, because the more irritating hummmm noise mostly disappeared, and most of what remained was the more benign white noise of wind turbulence.

At high load, the system is not quiet. The sound is dominated mostly by the 70mm CPU fan, which high speed whine can be easily heard over the the hard drive and the PSU fan. The latter appears to be much lower in level than the CPU fan. As noted earlier, this is a 275W model rather than the 200W model used in the EZ65. Perhaps its fan is set to speed up a bit more slowly under load because its components can handle higher temperatures.

Here are some audio recordings of the EX915 system as configured and tested.

  1. MP3 sound recording of EX915 system in idle: 30 dBA/1m
  2. MP3 sound recording of EX915 system at maximum load: 35 dBA/1m
  3. MP3 sound recording of EX915 system in idle with Samsung hard drive suspended: 28.5 dBA/1m

The recording (#3) with the suspended hard drive may sound as if the fans are spinning faster than the first recording with the HDD mounted normally. This is not the case. This overall higher pitched sound is the effect of the case vibrating.


The recordings above were made with a high resolution studio quality digital recording system. The microphone is 3″ from the edge of the fan frame at a 45° angle, facing the intake side of the fan to avoid direct wind noise. The ambient noise during all recordings is 20 dBA or lower.

A quick and simple way to use these recordings for valid listening comparisons is to play the quietest recording on only one speaker (or a pair of headphones) and set the volume so it is just barely audible a meter away. You must turn off any special sound effects, and set equalizer / tone controls to neutral or flat. Don’t touch the volume setting afterwards, and use the same one speaker when you listen to any of the other files. The end result will be reasonably close to the actual recorded sound levels.

Here is a recording of a very quiet sound that is barely audible from 1 meter away even in a super quiet room.

For full details on how to calibrate your sound system to get the most valid listening comparison, please see the yellow text box entitled Listen to the Fans on page 3 of the article SPCR’s Test / Sound Lab: A Short Tour.


In the XC Cube EX915, AOpen has taken the design used successfully in the EZ65 and adapted it to the 775 socket. From a performance point of view, the exercise works. Even with just the onboard video, the system’s performance is quite good, and it’s clear that the EX915 can be the equal of any 915-chipset based system. For 3D gaming, the main limitation will be the PCI Express video card chosen by the user. There is enough side-to-side ventilation to ensure good cooling of any video card. Use the best PCIe VGA with a high speed 775 socket processor, and you’ll have a great gaming rig.

Things are not so rosy if you seek a quiet PC. The question here is not whether the EX915 system is too noisy (which it is, for me). Rather, it’s whether ANY Intel Prescott-core CPU can be used in a SFF computer and maintain safe temperatures and low acoustics. The Intel 520 processor used in this review is about the slowest (read: coolest) socket 775 P4 available on the market, and it’s already at 100W. Any faster 775 processor will exhibit higher thermals, so the CPU fan speeds reached during the testing is about the lowest you’ll see in this system. Ditto the noise.

This is not to say manual control cannot make the EX915 a quiet PC, even with a hot Prescott. You can bypass the SilentBIOS Smart Control and use a hardware voltage controller to adjust the fan speed directly. This option is a bit more problematic than usual because you then need to monitor the CPU temp to establish a safe fan speed, but the temp sensors are not accessible in Windows. A motherboard BIOS upgrade might fix this, but the most recent one (mid-Nov 2004) did not. Still, as long as the system is stable, you know the temps are OK. The CPU heatsink / fan is actually reasonably smooth at lower speed so if it can be kept spinning slowly, it should be possible to keep the overall system noise down to under 30 dBA/1m at all times.

As with the EZ65, the EX915 AOpen SFF is attractive, well-finished and easy to assemble. However, we cannot recommend it if you seek low noise computing. If you really like the look of the case, choose an EX65 instead — it offers the socket-478 865 chipset based board in the same case. Not only are cooler Northwood core P4s still available, the fan controller in the 865-based AOpen SFF boards is about the best embedded in any motherboard.

Much thanks to AOpen for providing us the XC Cube EX915 sample and to for the Intel 520 CPU loaner.

* * *

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