On Abit IP35 Pro we could find these overclocking options (July 4th, 2007 BIOS):

• FSB clock: Can be adjusted from 133 to 600 MHz in 1 MHz steps.
• PCI Express clock: Can be adjusted from 100 MHz to 200 MHz in 1 MHz steps.
• CPU voltage: 1.3250 V to 1.8950 V in 0.01 V increments.
• Memory voltage: 1.800 V to 3.000 V
• DDR2 reference voltage: +2%, 0, -2%, -4%
• CPU HTT 1.2 V voltage: 1.20 V or 1.23 V
• North bridge voltage (“MCH 1.25 V Voltage”): 1.25 V, 1.29 V, 1.33 V, 1.37 V, 1.41 V, 1.48 V, 1.52 V, 1.56 V, 1.64 V and 1.72 V.
• South bridge voltage (“ICH 1.05 V Voltage”): 1.05 V, 1.09 V, 1.12 V, 1.15 V, 1.19 V, 1.25 V, 1.32 V and 1.38 V.
• South bridge I/O voltage (“ICHIO 1.5 Voltage”): 1.50 V, 1.55 V, 1.65 V, 1.70 V, 1.80 V, 1.90 V and 2.00 V.
• FSB voltage (“CPU GTLREF0&2” and “CPU GTLREF1&3”): 45% to 80% (this is the ratio between the CPU voltage and the FSB voltage).

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Figure 8: Overclocking adjustments.

This motherboard also provides some memory timings adjustments, as you can see on Figure 9.

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Figure 9: Memory timings settings.

On this motherboard there is no way to lock the memory clock at a specific clock rate, so overclocking the CPU you will automatically overclock the memory as well. This may be a problem as the maximum clock your memories can achieve may limit your overclocking. On the other hand, you can configure the FSB/memory clock ratio, so you may increase this when you think your memories are running at a too high clock.

The PCI Express clock configuration is also very important, as you can lock the PCI Express clock at a given value (100 MHz, for example). Usually when you increase the FSB clock you will automatically increase the PCI Express clock as well, and sometimes your overclocking will be limited not by the CPU but by the devices connected to the PCI Express bus. Thus with this option you can increase the probability of setting a higher overclocking.

The maximum external clock rate we could configure on this motherboard was 310 MHz, what made our memories to run at 930 MHz (FSB/memory ratio of 1:1.5). With this overclocking our Core 2 Duo E6700, which normally runs at 2.66 MHz, was running at 3.10 GHz, a 16.54% increase on its internal clock rate. With this overclocking our system performance increased 17.20% on Quake 4 and 10.19% on PCMark05.

We could configure our external clock above that but the system was unstable. We only consider our overclocking to be successful after we can run at least four times Quake 4 and PCMark05 with no errors.

We could achieve a better overclocking with several other socket 775 motherboards with no fancy adjustments: ASUS P5N-E SLU (327 MHz), Gigabyte GA-P35C-DS3R (324 MHz), ASUS P5B Premium Vista Edition (323 MHz), ASUS P5B (316 MHz) and MSI P35 Neo Combo (314 MHz).

We, however, didn’t play with voltage settings or any other fancy adjustments, so you may achieve a better overclocking than we did with more time and patience – on this motherboard and also on the other motherboards we reviewed.