How to enter the BIOS or CMOS setup

Updated: 03/06/2020 by Computer Hope
BIOS setup

Every computer provides a way to enter the BIOS or CMOS setup. This interface allows you to configure the basic settings of your computer.

Below is a listing of many common methods for accessing your computer's BIOS setup, and recommendations if you're having trouble.

Note

The details for your computer may be unique. If you're not sure, consult the owner's manual for your computer, or for your motherboard if the computer is custom-built.

Note

This page doesn't help if you cannot enter the CMOS setup because it's password-protected. For help with dealing with a CMOS password, see: How to clear an unknown BIOS or CMOS password.

New computers

Computers manufactured in the last few years allow you to enter the BIOS setup using one of the five keys shown below during the boot process.

Note

F1, F2, and F10 are all function keys on the top of the keyboard.

* If pressing F2 opens a diagnostics tool, your setup key is likely F10

** F10 is also used for the boot menu. If F10 opens a boot menu, your setup key is likely F2.

Setup keys are to be pressed as the computer is booting up. Most users see a message similar to the example below upon startup. Some older computers may also display a flashing block to indicate when to press the F1 or F2 keys.

Press <F2> to enter BIOS setup
Tip

If you're unsure of what key to press, as the computer boots try pressing and holding one or more keys on the keyboard to cause a stuck key error. Once you get this error, the option to continue or enter setup should appear.

Note

If you are still unable to enter the BIOS using the methods listed above, check the motherboard's manual for the appropriate key to enter BIOS. Documentation for the motherboard may also be on the manufacturer's website.

Once you have successfully entered the CMOS setup, a screen similar to the example below appears. Your CMOS setup may look different, depending on the manufacturer, but should still share a lot of the same options and information.

CMOS setup screen

How do I change and save changes in CMOS setup?

Once in CMOS setup, the method for changing the settings often depends on the BIOS manufacturer. You may use the arrow keys along with the Enter key to select categories and change their values. Some manufacturers may have you press the Page up and Page down keys to change the values.

Tip

All manufacturers show which keys navigate on the bottom or right side of the screen.

I cannot change the values to a setting I want to use

If you're trying to change the clock, speed, or other settings and don't have the option available, it's because the motherboard doesn't support it. If you believe it should be supported, you may need a BIOS update.

Tip

If changes you made appear to revert to default settings or the date and time setting in the BIOS keeps falling behind, you may need to replace the CMOS battery. For help with replacing the battery, see: How to replace the CMOS battery.

How do I save the changes?

If any changes are made, you need to save those changes, which is usually done by pressing the F10 key on the keyboard. If F10 doesn't work, look at the bottom or top of the screen for the key that's used to save the settings.

Older computers

Unlike the computers of today, older computers (before 1995) had numerous methods of entering the BIOS setup. Below is a listing of key sequences to press as the computer is booting to enter the BIOS setup.

  • Ctrl+Alt+Esc
  • Ctrl+Alt+Ins
  • Ctrl+Alt+Enter
  • Ctrl+Alt+S
  • Page Up key
  • Page Down key

Acer BIOS

If your Acer computer cannot boot or you want to restore the BIOS to its original settings, press and hold the F10 key as you turn on the computer. While continuing to hold the F10 key, two beeps should be heard indicating that the settings are restored.

AMI BIOS

Older AMI BIOS could be restored to bootable settings by pressing and holding the Insert key as the computer is booting.

BIOS or CMOS diskettes

Early 486, 386, and 286 computers required a floppy disk to enter the BIOS setup. These diskettes may be referred to as ICU, BBU, or SCU disks. Because these diskettes are unique to your computer manufacturer, you must obtain the diskettes from them. See the computer manufacturers list for contact information.

Early IBM computers

Some early IBM computers require you to press and hold both mouse buttons as the computer boots to enter the BIOS setup.

Other suggestions

Finally, if none of the above suggestions allow access to your CMOS setup, try generating a stuck key error, which gives an option to enter the CMOS setup. To do this, press and hold any key on the keyboard and do not let go (you may get several beeps as you are doing this). Keep pressing the key until the computer stops booting, and you have the option to enter setup. If this does not work make sure your keyboard is working.