A computer's processor, or central processing unit (CPU), is responsible for carrying out the millions of calculations that allow a computer to run. The faster a CPU runs, the more calculations it can handle each second, resulting in faster load times for programs and faster run time for processes. It is possible to change the run speed of your processor using your basic input output system (BIOS); a decrease in speed is known as underclocking, and an increase is known as overclocking.
Shut down your computer.
Start up the computer, and press the appropriate key to enter BIOS setup when prompted. A brief prompt should appear and indicate which key you must press to enter BIOS setup. Standard keys are the "delete" and "F" buttons. Sometimes the prompt is so brief you might not have time to find and press the key before your computer starts up. If this happens, restart and press the key immediately.
Use the navigation instructions in your BIOS setup utility to find management settings for FSB (front side bus) and FSB multiplier. These settings gauge how fast the processor is able to work. The exact menu names and navigation instructions you must find will vary depending on your BIOS and motherboard. Typically you will have to use the arrow keys to select categories, and "Enter" to open menus. "Escape" is often used to go back and exit BIOS at the main BIOS menu.
Alter the FSB speed and/or FSB multiplier. If you want to increase CPU speed, set the numbers so that your CPU speed increases by 10 to 20 percent. The menu should show your CPU clock speed, which will change when you alter the settings. If you want to underclock, do the same thing but use smaller numbers for FSB and/or the multiplier.
Change CPU voltage. If you alter the CPU run speed by changing the FSB speed, the CPU will require more or less power. Find a field for CPU voltage and alter it by a percentage similar to the change in CPU run speed.
Press the appropriate key to save your changes when you are finished, and exit BIOS to resume booting.
Changing the CPU run speed in your BIOS may cause system instability. Overclocking and underclocking is not an exact science and any changes to CPU speed should be made carefully. Record your original BIOS settings so you can change them back to default if problems occur.