CMOS and Power On Self Test POST Computer

A complementary metal oxide semiconductor (CMOS) is a type of integrated circuit technology. The term is often used to refer to a battery-powered chip found in many personal computers that holds some basic information, including the date and time and system configuration settings, needed by the basic input/output system (BIOS) to start the computer. This name is somewhat misleading, however, as most modern computers no longer use these chips for this function, but instead depend on other forms of non-volatile memory. CMOS chips are still found in many other electronic devices, including digital cameras.


In a computer, the chip controls a variety of functions, including the Power On Self Test (POST). When the computer’s power supply fires up, CMOS runs a series of checks to make sure the system is functioning properly. One of these checks includes counting up random access memory (RAM). This delays boot time, so some people disable this feature in the CMOS settings, opting for a quick boot. If installing new RAM it is better to enable the feature until the RAM has been checked.

Once POST has completed, CMOS runs through its other settings. Hard disks and formats are detected, along with Redundant Array of Independent Disk (RAID) configurations, boot preferences, the presence of peripherals, and overclocking tweaks. Many settings can be manually changed within the CMOS configuration screen to improve performance; however, changes should be made by experienced users. Changing settings improperly can make the system unstable, cause crashes, or even prevent the computer from booting.

The configuration screen is accessible during the POST phase of boot up, by pressing a key before the operating system initializes. Normally this is the Del key but it might be another. A line of text will indicate which key will take the user into the CMOS or BIOS setup screen. Changes cannot be made from within an operating system such as Microsoft Windows®, but must be made within a true DOS session. There is also an option to protect then settings by requiring a password to change settings. Changes are saved upon exit by pressing the F10 key, then the computer reboots to utilize the new settings.


Most motherboard manuals provide a complete list of available CMOS options. These will vary according to motherboard design and BIOS manufacturer.

The BIOS Basic Input Output System CMOS EEPROM

The BIOS (Basic Input Output System) is a software program that has been programmed (flashed) into an EEPROM module (integrated circuit, IC) mounted on the motherboard.


This program is not lost when all power is removed. This program is written by the BIOS/chipset/motherboard makers. It takes a special program to rewrite the BIOS firmware.

The CMOS is used by the motherboard chipset to save custom settings - changes to the BIOS firmware defaults, such as date and time, boot order, on-board device management, etc.

The CMOS memory module and the BIOS firmware EEPROM memory module work together to configure the motherboard to work with the attached hardware.


Up dating BIOS

Online Instructions	Download	Watch
Express BIOS Update	Download the .PDF	Watch the Video
F7 BIOS Flash Update	Download the .PDF	Watch the Video
iFlash BIOS Update	Download the .PDF
ISO Image BIOS Update	Download the .PDF
Recovery BIOS Update	Download the .PDF	Watch the Video
Integrator Toolkit BIOS Files	Download the .PDF

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Update the BIOS on your computer only if the newer BIOS version specifically solves a problem you have. Intel does not recommend BIOS updates for computers that do not need it. You can view all new BIOS fixes in the release notes included on the BIOS download page in Download Center.

Downgrading the BIOS to an earlier version is not recommended and might not be supported. An earlier BIOS version might not offer support for the latest processors, bug fixes, critical security updates, or support the latest board revisions currently being manufactured.

Before initiating a BIOS update, be sure to read and precisely follow the update instructions. You can open and print any PDF file from the online instructions table below for easy reference.

All images in the examples used in the instructions are for illustration purposes only. You need to select the correct BIOS files for your desktop board.

If a BIOS update process is interrupted, your computer might not function properly. Intel suggests the process be done in an environment with a steady power supply (preferably with UPS). If you have system issues after updating your BIOS version, see Troubleshooting BIOS Issues.

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BIOS updates will not make your computer faster, they generally won’t add new features you need, and they may even cause additional problems. You should only update your BIOS if the new version contains an improvement you need.

What’s a BIOS?

BIOS stands for basic input/output system. When you power your computer on, your BIOS takes control, starting the power-on self test (POST) and passing control over to the boot loader, which boots your computer’s operating system. The BIOS is low-level system software that should “just work” without getting in your way. Computers are now coming with UEFI firmware instead of the traditional BIOS, but the same is true for UEFI – it’s low-level system software with a similar role.
Unlike your operating system (which is stored on your hard drive), your computer’s BIOS is stored on a chip on your motherboard.