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Assembly & Overclocking

Tom's SBM: The $1,500 Mainstream PC

We were lucky this time; the build went off without a single hitch. We did invest some time into installing Swiftech’s H20-220—it wasn’t difficult, but you want to take your time when installing and testing liquid cooling.

With no leaks to fry our mainstream build, the system booted up straight away. Setting up RAID 0 was as easy as setting the option in the BIOS; the Vista install took over from there. After some testing, it was clear that the system was a strong performer for the price; so we ran the standard benchmarks and proceeded to overclock.


As we stated before, while our old Q6600 sample provided us decent but not awe-inspiring results in our last system builder marathon. We wanted to get our hands on a new Q6600 revision G0 sample to really see what these processors can do, before moving on.

With the H20-220 water-cooling system keeping temperatures low, we started by simply boosting the CPU voltage to 1.5 V, and increasing the front side bus speed from the stock 266 MHz to 400 MHz. These changes increased the CPU speed from 2.4 GHz to 3.6 GHz straight away.

To our glee, the system booted immediately and took us right to Windows. Everything seemed peachy until we ran the Prime95 stress test, which failed at about 18 minutes in. We played with the BIOS voltages, memory timings, memory speeds, and other settings, to no avail. Regardless of how willing it was to work in Windows, the CPU was not stable at 3.6 GHz. So much for our dreams of exceeding 3.7 GHz.

At the end of the day, we were forced to pull back to 3.456 GHz at an FSB of 384 to achieve total CPU stability. While this is an impressive 1 GHz faster than the stock speed of the Q6600—and will provide a massive gain in performance over that default—we have to admit that it’s time to look to other CPUs to reliably support higher overclocks. The E8400 may not share the Q6600’s four cores, but it will likely make it to speeds approaching 4 GHz; the higher speed will compensate well for the fewer cores, and two processor cores are the sweet spot for which most software is optimized anyway.

As for our Radeon 4850 graphics cards, the overclocks there were just as disappointing. The strange part was that the Catalyst Overdrive feature—which we usually find to be conservative—would validate the cards at an impressive 785 MHz GPU speed. However, using these speeds would crash the system once the Crysis benchmark was run.

We settled with a stable 700 MHz core and 1070 MHz memory overclock. This is not bad compared to a reference Radeon 4850’s core clock speed of 625 MHz, but not great considering these cards were already factory overclocked to 685 MHz out of the box.

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