Overclocking your processor can give your PC a significant speed boost - but you have to be careful. Here's how to overclock your system's processor without frying it.
Now let's look at manually overclocking an Intel Core i5-750. This quad-core CPU's default clock speed with all four cores running is 2.66GHz. We'll use the Gigabyte GA-P55-UD4 for our exercise. Once you understand how multipliers work, the manual process is pretty easy. Let's take a look at a typical BIOS setup screen.
To access the Gigabyte P55M-UD4 BIOS setup program, press Delete during bootup. We're concerned with three settings: 'CPU clock ratio' (the CPU multiplier), 'BCLK frequency' and 'System Memory Multiplier'. The default values are 20X for the CPU multiplier, 133MHz for the base clock, and 8.0 for the system memory multiplier.
We were able to easily push the Core i5 750 to nearly 3.5GHz by setting BCLK to 166MHz. This also pushed up the memory frequency to 1328MHz. Our more extreme overclock proved successful, but this system had already been running well for months with the following settings:
- CPU clock ratio: 20X
- BCLK: 150MHz
- System memory multiplier: 8X (yielding a memory speed of 1200MHz)
This particular setup has been rock-solid for us at 3.0GHz, running the stock Intel retail cooler.
Now let's look at the AMD system.
The Phenom II X6 1090T processor already runs at 3.2GHz, so pushing it up a couple of speed grades means running the system at 3.6GHz. So we'll set a limit of 3.6GHz using a fairly high-end CPU cooler, the £35 Thermalright Ultra 120 rev C with a fairly stock 120mm fan.
First, let's look at how the BIOS screen appears before we tweak the settings. The expandable screenshot at left shows this screen.
Although the settings for this AMD-based motherboard are similar to those for Intel-based motherboards, they are just a little different. The key items to consider for purposes of overclocking are the CPU ratio and the DRAM frequency.
The 1090T is clock-unlocked, so all we had to do was set the Ai Overclock Tuner to manual and change the CPU ratio from the default value of 16 to a new value of 18. In fact, AMD permits you to select incremental settings (for example, 16.5X multiplier), so technically our overclocked system is now running four speed grades faster.
Note that the only other change we made was to manually set the DRAM frequency to 1333MHz. That's it - and the system ran for several hours under stress testing.
NEXT PAGE: Stress testing