How to Underclock a PC

Access the computer's BIOS settings page (BIOS stands for "Basic Input Output System"). Depending on the brand of computer, this requires pressing keys during a certain time of the boot process. Some manufacturers require pressing "Delete" "F2" or + or other key combination while the system goes through POST (Power On Self Test) or displays a logo on the screen.

Locate "Frequency/Voltage Control" settings. BIOS screens generally consist of several pages of settings. Each page relates directly to certain parts of the computer operation. Use the "PgDn" and "PgUp" or "" arrow keys to navigate to the page that allows for adjustment of the above variables.

Scroll down to the "CPU Frequency/Voltage Control." Press "Enter" or use the left and right arrow keys to select the value. Use the arrow keys, + and - keys or other combination to adjust the value lower.

Lower the CPU clock speed. Lower these values similar to the way described above. Note that the performance decreases linearly to the clock speed.

Lower the core voltage (vCore). Lower these values similar to the way described above. In the CPU's spec it will mostly behave linearly, so a 10% decrease in voltage will need about a 10% decrease in clock speed.

When complete, be sure to save the settings before exiting, otherwise the old settings will remain in place. If you think you've made a mistake, press the "Esc" key to exit without saving.Note: Not all computer BIOS have "Frequency/Voltage Control" settings, maybe lock by Manufacturers.