Dell XPS 720 H2C

Verdict: Quiet and power-efficient, but a little lacking in performance.

Although Dell has been selling XPS-branded PCs since 1993, up until recently they were nothing more than standard Dimension PCs with a slightly higher spec and a few extra lights. The 720 H2C, on the other hand, is a completely different beast. Admittedly, it isn't the first XPS to make use of the XPS 700 chassis, but it's Dell's first PC to be shipped overclocked. This is a pretty massive step forward for the world's largest PC manufacturer, so for the first time, we thought it would be worthwhile to invite the company to take part in our annual Dream PC Labs test.

The 720 H2C comprises an eclectic mix of cutting-edge and older components. For example, while the hard disks, optical drive and monitor are barely a few months old, the CPU made its first appearance in early 2007. The CPU in question is a 2.93GHz quad-core Core 2 Extreme QX6800. The QX6800 is the better part of six months old, but it's no slouch, as Dell has overclocked it to 3.46GHz by raising its multiplier from 11 to 13. Amusingly, this means that although the CPU in the Dell was initially slower than the CPU fitted to the Gladiator, it's overclocked further.

Raising the multiplier is the easiest way to overclock a CPU but, as quad-core CPUs are so bandwidth-hungry, we'd like to see Dell overclock future XPS systems by raising the FSB. It's possible that Dell hasn't done this because it supplies very basic RAM with the 720 H2C. The 3GB provided takes the form of four PC2-5300 DIMMs (two 1GB and two 512MB), so the CPU has far less memory bandwidth with which to play than the other Dream PCs. As we went to press, Dell informed us that by the time you order the system, it should be supplied with faster PC2-6400 RAM, which should help to boost the system's performance.

The reason Dell has felt confident enough to overclock the CPU is that it has developed a new high-tech cooling system. This is known as the H2C, and takes up almost half of the case. The H2C works like a standard water-cooling system in that it pumps coolant through a waterblock mounted on top of the CPU. However, any similarities end there; instead of relying on a simple radiator and fan to extract heat from the coolant, the H2C employs a two-stage cooling process. Firstly, the coolant passes through a 120mm-fan radiator before passing through a heat exchanger that uses two low-wattage TECs to transfer heat from the coolant into the exchanger's fins. As a result of this two-stage process, the H2C provides very effective cooling at a low noise level. In our stress test, the CPU temperature maxed out at just 63ûC - far cooler than the CPUs in any of the other Dream PCs.

The rest of the components inside the chassis are cooled according to the BTX specification, so the 720 H2C looks very different from most PCs. For example, the Northbridge appears to be fitted with a simple heatsink, but it's cooled by air flowing from the exhaust of the H2C. The graphics cards are fitted with standard GeForce 8800-series HSFs, although a 120mm fan blows cool air over the ends of the cards. Unlike the other Dream PCs, the graphics cards are held in place by a massive bracket, so they shouldn't come flying out while the PC's in transit. The XPS 700 chassis looks great, with a highly reflective black finish. Although there's no viewing window, several LEDs are dotted around the case, and you can change the colour of these in the BIOS. However, the front of the case is a real letdown. From a distance, the air grille looks great but, rather surprisingly, it's made from thin plastic, not metal, so it rattles about. Worse still, the plastic covers for the 13-in-one memory card reader, floppy and disc drives are so flimsy that they feel as if they would break after a few months.

As the motherboard sports the nForce 680i SLI chipset, the 720 H2C employs two GeForce 8800 GTX graphics cards running together in SLI. Rather disappointingly, these cards aren't pre-overclocked, so they run at the standard frequencies recommended by Nvidia. The cards output their signal to a massive Dell 2707 WFP monitor, a 27in 1,920 x 1,200 TFT. Unfortunately, although this monitor looks attractive, it produces unnatural-looking colours. As HD movies are still thin on the ground, Dell hasn't fitted a Blu-ray or HD-DVD drive to the 720 H2C, instead opting for the more sensible combination of a separate DVD writer and DVD-ROM. Sticking with the sensible theme, two Hitachi 1TB drives are also fitted; unlike the Gladiator, though, these aren't configured in a highly vulnerable RAID 0 array. Powering all these components is a massive 1kW Dell PSU, which remains pleasantly quiet even when the system is running at full throttle. Also along for the ride is a Logitech G15 keyboard, Logitech Z-5500 Digital speakers and a Dell-branded mouse, which proved to be very unsuited to frantic mouse panning when gaming. Feeding the speakers is a Sound Blaster X-Fi Xtreme Music; unlike the other Dream PCs, this is connected to the front panel's audio jacks, so you don't need to mess around behind the case when plugging in your headset.

As Dell has opted to fit 3GB of RAM to our 720 H2C review sample, the pre-installed 32-bit version of Vista Ultimate appears to be a sensible decision, since the 32-bit version of Vista is limited to using a maximum of 3.12GB. The 720 H2C is very power-efficient, drawing 502W from the mains at full tilt, which is around 30 per cent less than the Scan White Cobra.

Performance

Although the QX6800's default configuration is the slowest of the CPUs supplied with this year's Dream PCs, Dell has overclocked it by 466MHz. Unfortunately, although it's overclocked higher than the CPU in the Gladiator (3.46GHz compared to 3.33GHz), the low-bandwidth PC2-5300 RAM acts as a brake on the 720 H2C's overall performance. For example, it proved to be slower than the Gladiator in our video encoding and multitasking tests, and only managed a score of 1,171 in our image editing test.

The 720 H2C was very similar in performance to the Gladiator in games as well. This is due to the faster CPU of the Dell being counterbalanced by the faster graphics cards of the Gladiator. Nonetheless, the 720 H2C proved to be capable of playing most of our test games smoothly, apart from Flight Simulator X. Unfortunately, Dell doesn't automatically install every Windows update, such as hotfix 936710, which enables multi-GPU support in DirectX 10 games. As it also installs only WHQL-approved drivers, the 720 H2C was slower than the Scan White Cobra in World in Conflict and Company of Heroes. A few software updates would narrow the gap, but the Scan, with its more powerful CPU and overclocked graphics cards, still has the edge.

The BIOS allows you to raise the bus multiplier above 13, and increases the CPU voltage as you do this. However, every time we boosted the multiplier to 14, we saw the BSOD just after Vista reached the desktop, so clearly Dell has pushed the 720 H2C as far as it will go.

Conclusion

The Dell XPS 720 H2C looks great, in an understated sort of way. Unfortunately, the build quality of the plastic front panel leaves a lot to be desired, SLI support is very hit-and-miss and the choice of low-performance PC2-5300 RAM leaves the overclocked quad-core CPU gasping for memory bandwidth. Still, it's a powerful and distinctive PC and a much better choice than the noisy Gladiator.