Hands on: Overclocking a Core 2 Duo

Intel’s Core 2 Duo processor brings many benefits to desktop systems. I compared the E6700 model against an older Pentium 4 and it scored well in terms of speed, power consumption and temperature. But the big question is, how well does it overclock?

To measure the E6700’s overclocking potential I selected the Asus P5W DH Deluxe motherboard. This features an eight-phase power design, which reduces stress on the CPU and power components, allowing both a cooler system and greater overclocking potential.

The P5W DH Deluxe is ideal for anyone wanting to get the most from an LGA 775 processor, but if you want to support the latter, you’ll need a recent version of the motherboard which specifically states it’s ‘Core 2-Ready’, and ensure it’s running the latest Bios.

I’d be increasing the front-side bus (FSB) to overclock the processor, so I needed memory that could keep up. The Core 2 Duo E6700 runs on a 266MHz external bus, meaning DDR2 memory would operate at 533MHz.

PC2-4200 DDR2 is designed to run at 533MHz, but if you’re going to overclock and keep the memory synchronous, you’ll need faster modules. I selected a pair of 1GB Crucial Ballistix DDR2 PC2-6400 Dimms. These would support an external bus speed of 400MHz, or 50 per cent higher than the Core 2 Duo’s standard external speed.

The rest of the rig matched this month’s Hardware configuration: a Gigabyte NX66256DP Nvidia Geforce 6600 PCI-Express graphics card and a 400GB Seagate Barracuda 7200.8 hard disk loaded with Windows XP Media Center Edition 2005. Providing air-cooling duties was Zalman’s substantial CNPS9500 heatsink.

Pentium 4 comparison
For comparative purposes, I first fitted the motherboard with an older Pentium 4 660 model. Clocked normally at 3.6GHz, this scored 217 in Sysmark 2004.

This processor runs on an 800MHz FSB, which is clocked at 200MHz externally; this external figure is the one to increase in the motherboard Bios for overclocking. I upped it to 220MHz, which drove the processor at 3.96GHz; it booted fine and scored 226 in Sysmark.

In previous tests this was as far as I’d managed to overclock this particular processor, so it was with some trepidation that I increased the bus further. I needn’t have worried though, as with the bus running at 230MHz the system started fine, with the CPU clocked at 4.14GHz where it scored 240 in Sysmark.

Overclocking the processor to 4.33GHz using an external 240MHz bus was a step too far and it refused to run the benchmarks even when fed a higher core voltage. It was happy though at 4.24GHz using a 235MHz bus, whereupon it scored 244 in Sysmark. As the motherboard was the only different component since my last tests, I can thank the Asus P5W DH Deluxe for the extra overclocking potential.