Editor's Note: We head into another multi-day System Builder Marathon (SBM); this time focusing on overclocking. If the first SBM produced a bunch of sleepless editors all over the US and Canada, this one led to even more sleep deprivation for our authors, Thomas Soderstrom, Don Woligroski and Shelton Romhanyi. Overclocking can quickly turn even the most stable individual into a raving maniac. Finding just the right combination of timings for optimal performance and successful benchmarking runs, can take days, or more correctly days and nights. If that was all, it would only be bad. But, when components start going south and have to be replaced, bad becomes stinkingly terrible. At this point everyone's pretty much over the horrors of overclocking and ready to show off their work. So, let the overclocking games begin.

At the completion of our System Builder Marathon, one of the most frequently asked questions we received concerned the overclocking potential of the three systems we built. Before we had the opportunity to investigate the overclocking potential of any of our systems, though, Dell's XPS 720 H2C factory-overclocked PC arrived in the labs with a tight release deadline. Compare Prices on Dell XPS Notebooks

Built expressly for overclocking, Dell's factory-overclocked and water-cooled quad-core PC came with the promise of "more room" to achieve even higher clock speeds, but getting there would require some work. This could have been the perfect opportunity for lab technician Shelton Romhanyi to get some overclocking experience, if not for the tight deadlines of other articles already in progress.

Dell's factory-overclocked quad-core was better equipped than any other machine in the lab, and the closest matching point of comparison was the high-end dual-core build from our System Builder Marathon, Day 3. We still hadn't had a chance to overclock our own system, so those readers still waiting for overclocking results were justifiably incensed to see Dell's overclocked system taking on ours at stock speed.

Even so, we couldn't leave our enthusiasts hanging out to dry, and our tight publishing schedule finally loosened enough to allow further overclock testing. First up is the system with the least room for improvement: Dell's XPS 720 H2C; we'll follow up tomorrow with the overclock results of our own system. Series co-editor Don Woligroski will join in with his own low-cost system, to show the value side of overclocking, and we'll finish up by comparing all three systems on a bang-for-the-buck basis.

Overclock Settings

Dell doesn't allow its end users to modify voltage levels, even on its overclocking machine. The system arrived with the CPU at a fixed 1.60 volts.

Dell had pre-overclocked its Intel Core 2 Extreme QX6800 from 2.93 GHz to 3.73 GHz by raising the multiplier from 11x to 14x. Quad core processors are usually more difficult to overclock than dual cores, so Dell's images of an XPS 720 H2C clocked to 4 GHz caused quite a stir. These kinds of settings were impossible to achieve on the system they sent, however - Shelton was only able to increase the stable processor speed from 14x 266 to 14x 271. The CPU topped out at 3.794 GHz, in the same neighborhood of what many unnamable-but-experienced sources told us would be this processor's limit.

With so little wiggle room in overclocking the CPU, the next step was to look for better RAM timings. Increasing the CPU FSB clock to 271 MHz (FSB1084) had already increased the memory speed from DDR2-1066 to DDR2-1084. Dell's stock latencies of 5-5-5-15 were far from the limits of the included Corsair CM2X1024-8500C5D modules, and Shelton was able to lower these to 5-4-4-8.

The final chance to look for big gains came from the graphics cards, where Shelton was able to increase GPU and RAM frequencies from Dell's 612 MHz and 2160 MHz data rate to 660 MHz with a 2320 MHz data rate.

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