What is the BIOS?

The BIOS is a piece of software that is permanently stored in a chip on the motherboard. When you first turn on a computer, the BIOS program is initiated. It performs a hardware check and makes sure that certain crucial pieces of hardware are present and functioning properly. For example, it makes sure there is a video card, a CPU, memory, and a power supply providing proper voltages. If there is a problem, it will inform you via beep codes. If everything is fine, it will display a startup screen, the first thing you see on your monitor. It then proceeds to do a memory check, discover other hardware, configure devices as needed, identify the boot drive, and then hand over control to the boot sector on the boot drive, which launches the operating system.

What does "flashing the BIOS" mean?

This BIOS software is in some regards like other software. There are newer versions available that contain updates, enhanced, features, new features, and bug fixes. It is possible to install newer BIOS versions and upgrade, but the process is different from upgrading regular software that's installed on your computer. The BIOS software is not stored on the hard drive, but in a chip on the motherboard. To erase the software on the chip and program it with a newer software version you need to use a special program called a flash utility, and the process of performing the upgrade is called flashing the BIOS.

Why would you need to flash the BIOS?

The most popular reasons that cause people to flash the BIOS are


  • Support for newer processors - The BIOS allows the motherboard to accept processors up to a certain speed. Since you got the computer, the top speed of the processor type your computer accepts has increased. You decide to replace your processor with a faster one, but the BIOS does not recognize it or does not have the right settings. Upgrading the BIOS can resolve this problem.
  • Support for bigger hard drives - The BIOS allows the motherboard to accept hard drives up to a certain size. Since you got the computer, the maximum size for hard drives has increased. You decide to install a newer and bigger hard drive, but the BIOS does not recognize it or only recognizes part of the drive. Upgrading the BIOS can resolve this problem.
  • Bug fixes - The BIOS contains certain features and options, but one of them does not function properly or not at all. Since you got the computer, the manufacturer has recognized and corrected the problem with a new BIOS version. Upgrading the BIOS can resolve this problem.

The hazards of BIOS flashing

As described earlier, the BIOS is a crucial component of your computer since it is always the first program that runs when you turn the machine on. If the BIOS does not run, the machine cannot boot. Therefore it is very important that a BIOS upgrade is performed properly. If it fails, it can permanently ruin the BIOS, resulting in your computer becoming a door stop. Common reasons for BIOS flashes gone bad are power failure during the flashing process, and flashing the BIOS with an incorrect BIOS version. Because of these dangers you do not flash a BIOS just for shits and giggles, but only if there is a very good reason.

How to fix a ruined BIOS chip

If a flash has gone horribly wrong and the computer fails to boot altogether, the only solution is to replace the BIOS chip on the motherboard with a new one that contains a healthy and correct BIOS. To obtain a new BIOS chip, contact your motherboard manufacturer and give them the model of your motherboard. For a relatively small price ($10-15 plus shipping) they may mail you a new BIOS chip. To install the new chip, you open up the computer after taking appropriate anti-static precautions, identify the BIOS chip on the motherboard with help of the manual, carefully pull the old chip out of its socket, and insert the new chip in its place. Be sure to carefully follow the manufacturer's installation instructions.

However, be aware of the fact that some manufacturers will not sell individual BIOS chips, and some older motherboards have non-replacable BIOS chips. In those two cases you will be forced to replace your motherboard, which is expensive and somewhat of a hassle.

While BIOS flashing requires some care and preparation, it is a relatively simple process if done right. Let's go over the steps of properly flashing a BIOS using a real-world example, the motherboard BIOS in my test machine.

Note: Please keep in mind that the following steps are an example to help you understand how the process works. However, your motherboard and BIOS version are most likely different from mine and you will have to adjust your steps, download files, and command line switches accordingly. Please exercise caution when flashing your BIOS and stop and ask for help if you are not certain.

1 - Identify your motherboard and BIOS

The first step is to find out what motherboard and BIOS you have. We have a comprehensive article on how to identify your motherboard in our how-to section, you can find the article here: It also covers information on identifying your BIOS.

While there are a lot of motherboard manufacturers, there are two main BIOS companies out there: AMI (American Megatrends) and Award. Most motherboards use one of these two BIOS types. Both BIOS types display the BIOS identifier number on the main BIOS screen you see when you start the computer.

Tip: Push the Pause/Break key on your keyboard after the BIOS screen appears. It will pause the BIOS program and give you time to look over the screen to identify and document the BIOS number. Press Enter to continue.

Tip: There is a program available that is able to identify the BIOS from within Windows. It is called BIOS Agent and can be downloaded here:


In the example used for this article the BIOS is an Award BIOS. The identifier string is located at the bottom and looks like this: 11/08/1999-i440BX-W83977-2A69KA1UC-PL

This gives us the following information:


  • 11/08/1999 is the date of the BIOS
  • i440BX indicates that the motherboard is using the Intel 440BX chipset
  • 2A69K also identifies the chipset as an Intel 440BX/ZX
  • A1 indicates that the motherboard was made by Abit
  • UC identifies the board as the model BE-6
  • PL is the BIOS version

Now that we know the motherboard model and the BIOS version, the next step is a visit to the Abit website to check for a later BIOS version.

2 - Download the updated BIOS file and flash utility

Sure enough, there have been three new BIOS releases for this particular motherboard. According to the release notes they fixed three bugs, improved IRQ assignment, and offered support for faster processors. The most recent BIOS version is TH.


Note: You do not have to flash every single update, only the most recent one. It contains all previous updates.

Download the BIOS file to the hard drive. It is a self-extracting executable. After double-clicking it extracts the actual BIOS BIN file, in our case called BE6_TH.BIN, which contains the new BIOS software.

In order to perform the flash, we also need the Award flash utility. This program performs the task of erasing the old BIOS from the chip and uploading the new BIOS. We download this file called awdflash.exe to the hard drive as well.

3 - Prepare a clean DOS boot disk

A BIOS flash needs to be performed from a true DOS environment. The only way to get a clean plain DOS environment is by booting from a DOS boot floppy. You can download a DrDOS boot disk from Execute the downloaded file to create a DOS boot floppy. Please use a good quality new floppy disk to minimize the risk of the BIOS flash failing due to corrupted files on the floppy.

Note: Yes, there are now programs that supposedly allow flashing certain BIOS's from Windows. Yes, there are ways to perform the flash from the hard drive instead of floppy disk in certain situations. However, these situations do not apply to every single computer. The method of booting and flashing from a floppy disk described here is by far the most common one.

Once the DOS boot disk has been created, copy both the BIN file as well as the flash utility to the floppy disk.


Be sure to reboot with the disk at least once before the flash process to confirm the disk works properly.

4 - RTFM - Read the freakin' manual!

Before you go any further, make sure you read the manual, specifically the instructions for BIOS flashing. It will explain how to use the flash utility and all the command line switches it uses. It is important that you understand what command to run to perform a proper BIOS flash.

In this example I decided to use the following command after reading the manual:


Here's what this command does in this case:


  • Awdflash is the name of the utility
  • BE6_TH.BIN is the name of the new BIOS BIN file to be uploaded
  • /PY is the command to program the flash memory
  • BE6_PL.BIN is the name of the file as which the old BIOS will be backed up to the floppy disk
  • /SY is the command to back up the old BIOS to the floppy
  • /CD is the command to clear the DMI data after programming
  • /CP is the command to clear the Plug'n'Play data after programming
  • /CC is the command to clear the CMOS data after programming

The reason I am clearing all the existing data is because I want to start with a nice clean slate and verify or configure all BIOS settings after the flash.

Again, read the instructions carefully, make sure you understand them, prepare the command line you will use for the flash process, and write it down on a piece of paper.

5 - Last preparations

As mentioned before, the most common reasons for a failed BIOS flash are uploading the wrong file and having power dips or failures during the flash causing the computer to reboot during the procedure, wrecking the BIOS for good.

You protect yourself against the incorrect BIN file by carefully double-checking your work, making sure you correctly identified your motherboard and BIOS, and downloaded the appropriate BIOS update file.

To make sure that a power failure doesn't ruin your BIOS, plug your computer into a UPS (Uninterruptable Power Supply) that will provide battery power in case of power failure. More on UPS in this article:

Reboot your machine and press the appropriate key to enter your BIOS. Typical keys to access the BIOS are (by manufacturer):

AMI - F1, Del, Ctrl-S
AST - Ctrl-Alt-Esc
Award - F1, F2, Del, Ctrl-Alt-Enter
Compaq - F10
Phoenix - F2, Ctrl-Alt-Esc, Ctrl-Alt-R, Ctrl-Alt-Ins, Ctrl-Alt-Q, Ctrl-Alt-F1, Ctrl-Alt-+, Ctrl-Alt--
IBM - PS1 Ctrl-Alt-I

Now go through every single page and carefully document the current BIOS settings. This step is very important because after the BIOS flash some or all of the settings will be gone and you will have to reconfigure it manually.

Tip: If you have a digital camera, use it to take pictures of each BIOS screen. It's a lot quicker than writing down each setting by hand.


While you're in here, take a look at the boot sequence and make sure the floppy disk drive is set as the first boot device.

6 - Performing the BIOS flash

Now that we're thoroughly prepared, it's time for the actual procedure.

Insert the boot floppy you prepared and restart your computer. You will end up at a DOS prompt for the floppy drive A:\.

At the A:\ prompt, type the command line you prepared earlier to run the flash utility and program the BIOS.


Since you already provided all the details via switches, the flash program should run without interruption. First it backs up the current BIOS to a file on the floppy disk.


Then it programs the BIOS chip with the new BIOS.




The process is very quick and uneventful. It took less than a minute to flash this BIOS, no user input required, and it went smoothly.

Now it is time to reboot. Watching the screen after the reboot we can now see the updated BIOS version TH in the BIOS identifier string at the bottom.


Immediately go into the BIOS after the reboot, do not let the operating system boot yet. In the BIOS, go through each screen and configure it with the proper settings that you documented earlier. Double-check all the settings for accuracy. Misconfiguring the BIOS can lead to system instability or hardware failure, so be thorough.

Once the BIOS is configured properly, reboot one more time, and this time let the operating system boot as usual. Everything should come up normally. It is possible that Windows might announce that it found new hardware and starts installing drivers. That's ok, it is a result of the Plug'n'Play data being cleared during the BIOS flash. Since all your hardware was already installed before the flash and Windows has all the drivers, it should automatically install them without incident. You might be prompted for one last reboot after this is done.

You've successfully flashed your BIOS

As you can see, flashing the BIOS is not as scary or mysterious as it may sound. It is a process consisting of a simple series of logical steps. Performing these steps with care, patience, and preparation will minimize the risks of the procedure.

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Copyright © 2002 Øyvind Haugland
Sist endret:  13 januar 2019

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