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Home > BIOS Systems > BIOS Index Pages > Introduction To BIOS Upgrades
These pages will provide an understanding of what the Basic Input Output System is and how it works in a personal computer.
On This Page:
Introduction To The Basic Input Output System The Power On Self Test (POST Routine) CMOS Settings What's On Board?
How Operating Systems Work BIOS Upgrades Page BIOS Beep Codes
Video Demonstration
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Introduction To BIOS Upgrades

There is a wide variety of reasons why someone would need to complete a BIOS upgrade to their computer. The most common reason is to resolve compatibility problems. For example, as stated on a previous page within this section, some motherboard BIOS versions do not provide support for hard disk drives larger than a 137 GB capacity. This problem is easily resolved through an upgrade of the system BIOS.

Computer manufacturers typically tailor or modify their BIOS to provide special capabilities. The original manufacturer of the BIOS does not have these modifications, and thus an upgrade from them could disable key functions on your system or make it inoperable.

Be advised that the important issue is to get the BIOS update from the manufacturer of your computer unless they explicitly recommend you go to the BIOS manufacturer for the fix. Done improperly, it may render the motherboard useless requiring, at minimum, a return to the manufacturer or distributor for repair.

Upgrading the BIOS

Motherboard manufacturers tailor the BIOS code to the specific hardware on each board. This is what makes upgrading a BIOS somewhat problematic; the BIOS usually resides in one or more ROM chips on the motherboard and contains code specific to that motherboard model or revision. In other words, you must get your BIOS upgrades from your motherboard manufacturer or from a BIOS upgrade company that supports the motherboard you have, rather than directly from the original core BIOS developer.

Although most BIOS upgrades are done to fix bugs or problems, you must often upgrade the BIOS to take advantage of some other upgrade. For example, a BIOS upgrade often adds support for newer processors, larger internal hard drives, bootable optical and USB drives, faster booting, and more.

Part of the PC 2001 standard published by Intel and Microsoft requires something called Fast POST to be supported. Fast POST means that the time it takes from turning on the power until the system starts booting from disk must be 12 seconds or less. This time limit includes the initialization of the keyboard, video card, and ATA bus. For systems containing adapters with onboard ROMs, an additional 4 seconds are allowed per ROM. Intel calls the Fast POST feature Rapid BIOS Boot (RBB)and is supported in all its motherboards from 2001 and beyond—some of which can begin booting from power-on in 6 seconds or less.

If you install newer hardware or software and follow all the instructions properly but you can’t get it to work, specific problems might exist with the BIOS that an upgrade can fix. This is especially true for newer OSs. Many older systems need to have a BIOS update to properly work with the Plug and Play and ACPI power management features of Windows. Because these problems vary from board to board, it pays to periodically check the board manufacturer’s website to see whether updates are posted and what problems they fix. Because new hardware and software that are not compatible with your system could cause it to fail, I recommend you check the BIOS upgrades available for your system before you install new hardware or software—particularly processors and OSs.

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Where to Get Your BIOS Update
You must download most BIOS upgrades from the system or motherboard manufacturer's website. The BIOS manufacturers do not offer BIOS upgrades because the BIOS in your motherboard did not come directly from them. In other words, although you think you have a Phoenix, AMI, or Award BIOS, you really don't! Instead, you have a custom version of one of these BIOSs, which was licensed by your motherboard manufacturer and uniquely customized for your particular motherboard. As such, you must get any BIOS upgrades from the motherboard or system manufacturer because they must be customized for your board or system as well.
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Determining Your BIOS Version
When seeking a BIOS upgrade for a particular motherboard (or system), you need to know the following information:
  • The make and model of the motherboard (or system)

  • The version of the existing BIOS

You usually can identify the BIOS you have by watching the screen when the system is first powered up. It helps to turn on the monitor first because some take a few seconds to warm up, and the BIOS information is often displayed for only a few seconds. You usually can press the Pause key on the keyboard when the BIOS ID information is being displayed, which freezes it so you can record the information. Pressing any other key allows the system startup to resume.


Many PCs do not display the typical POST screen. Instead, they show a logo for the motherboard or PC manufacturer, which is usually referred to as a splash screen. To enter BIOS Setup, you must press a key or keys (specific to the BIOS manufacturer). You might hear some in the industry refer to displaying a manufacturer’s logo instead of the default POST screen as a quiet boot. Often you can change these BIOS splash screens to your own liking, even including your own company logo or graphic of choice. Intel has free BIOS customization software called the Intel Integrator Toolkit ( that enables you to change or restore the splash screen on Intel motherboards, as well as customize many other BIOS settings. Other motherboard manufacturers also offer logo or splash screen customizers; for example Gigabyte has a logo utility called Face-Wizard ( for its motherboards.


To determine your current BIOS version, look for any copyright notices or part number information on the screen during the POST. Sometimes you can press the Pause key on the keyboard to freeze the POST, which allows you to take your time to write down the information. Pressing any other key then causes the POST to resume. In many systems you can also find the BIOS ID information in the BIOS Setup screens. Finally, you can use a program like SIW (System Information for Windows) to report the BIOS version as well as the supported features. SIW is available free from

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Checking the BIOS Date
One method of determining the relative age and capabilities of your motherboard ROM is to check the date. The BIOS date is stored in virtually all PCs as an 8-byte text string at memory address FFFF5h. The date generally indicates when the BIOS code was last updated or compiled by the motherboard manufacturer. Knowing the date of a particular BIOS might give you some clue as to which features might or might not be present. You can use the DEBUG command-line utility supplied with Windows and DOS to view these addresses. DEBUG is a command-line program that presents a prompt of its own, to which you can enter various commands. For example, the ? command displays help information. To find the BIOS date, open a command prompt and execute the DEBUG command. Then at the DEBUG - prompt, enter D FFFF:5 L 8, which instructs DEBUG to display memory at FFFF5 for a length of 8 bytes. DEBUG then displays both the hexadecimal and ASCII codes found at those addresses. When the - prompt returns, you can enter Q to quit DEBUG and return to the command prompt. Figure 5.6 shows how this looked when I ran it on one of my systems.

Figure 5.6. Using DEBUG to display the motherboard ROM BIOS date.

In this example, the system shows a motherboard ROM BIOS date of 03/22/05.
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Backing Up Your BIOS

Before updating a BIOS, it is generally a good idea to see if it is possible to save a backup copy of the existing BIOS. That is because some motherboard manufacturers only offer the latest BIOS for a given motherboard; sometimes a newer BIOS may cause problems or have consequences you are not ready to live with. By having a backup, you can go back to the previous version. To make the backup, run the BIOS upgrade program for your board, and check to see if there is an option to save the existing BIOS to a file. If that option is not available, check to see if your motherboard manufacturer offers older versions (including the one you have) for download.

If there is no menu option to back up and no older versions can be downloaded, there may be other ways to make a copy of the BIOS, such as by using the DOS command–based BIOS upgrade software usually found on the BIOS upgrade floppy or CD for the motherboard. For example, if your motherboard has a Phoenix or Award BIOS, you can create a backup using the awdflash.exe program found on the BIOS upgrade disk for your motherboard with the /sy (Save Yes) and /pn (Program No) parameters, as follows:

awdflash /sy /pn

When the program runs, you are prompted to enter the backup file’s name (for example, backup.bin). Press Enter to save the file.

Backing Up Your BIOS Setup (CMOS RAM) Settings

A motherboard BIOS upgrade often wipes out the BIOS Setup settings in the CMOS RAM. Therefore, you should record these settings, especially important ones such as hard-disk related settings and parameters. Some BIOS Setup programs offer the ability to save and restore CMOS settings, but unfortunately this capability is not universal. In some cases the new BIOS offers new settings or changes the positions of the stored data in the CMOS RAM, which means a backup and restore won’t work.

Although it sounds like a simple concept, actually saving the BIOS Setup settings is somewhat difficult technically because the amount, type, and even location of information stored in the NVRAM (nonvolatile RAM) can vary considerably from one motherboard to another. That being said, there are some possibilities, but they generally won’t work with all types of systems.

For example, Lenovo provides both Windows and DOS-based BIOS Settings Capture/Playback Utilities, but these work only on newer ThinkPad laptops. For other systems there are more generic solutions that might work, such as the following:

Unfortunately, these don’t work on all systems, but they are free to try and use.

In many cases, you are better off manually recording your BIOS Setup parameters. One easy way to do this is to use a digital camera to take pictures of each screen or menu. If you have a parallel printer connected, which is admittedly unlikely, you also might be able to print the screens using the PrtScr key on the keyboard. Turn on the printer, start your computer normally, and restart it without turning off the system to initialize the printer. Note that this won’t work for printers connected via USB because only parallel printers are directly supported via the BIOS. When recording any changes you made from default settings, pay special attention to any hard drive settings, especially SATA modes (IDE/AHCI/RAID), drive geometry (cylinder/head/sectors per track), or translation (LBA, Large, CHS). These are important because, if you fail to reset them as they were, you might not be able to boot from or access the drives.


If you use a digital camera to take a picture of each BIOS setup screen, be sure to set the camera to its close-up mode. Also, unless the camera is an SLR (Single Lens Reflex) type, use the camera’s LCD screen rather than the optical viewfinder to ensure you get the entire BIOS screen in the photo.

Keyboard Controller Chips

In addition to the main system ROM, some systems have a keyboard-controller microprocessor with its own built-in ROM. The original keyboard controller was an Intel 8042 microcontroller, which incorporates a microprocessor, RAM, ROM, and I/O ports. This was a 40-pin chip that often had a copyright notice identifying the BIOS code programmed into the chip. Modern motherboards have this function integrated into the chipset, specifically the Super I/O or South Bridge chips.

The keyboard controller controls the reset and A20 lines and deciphers the keyboard scan codes. The A20 line is used in extended memory and other protected-mode operations.

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Upgrading a Flash BIOS
Virtually all PCs built since 1996 use a flash ROM to store the BIOS. A flash ROM is a type of EEPROM chip you can erase and reprogram directly in the system without special equipment. Older EPROMs required a special ultraviolet light source and an EPROM programmer device to erase and reprogram them, whereas flash ROMs can be erased and rewritten without you even removing them from the system. On some systems, the flash ROM is not a separate chip but may instead be incorporated into the South Bridge chip.

Using flash ROM enables you to load the upgrade into the flash ROM chip on the motherboard without removing and replacing the chip. Normally, these upgrades are downloaded from the manufacturer’s website. Depending on the design, some update programs require that you place the software on a bootable floppy or optical disc, whereas others configure the program to run on the next startup (before Windows loads), and still others actually run in Windows as a Windows application.

Some systems allow the flash ROM in a system to be locked (write-protected). In that case you must disable the protection before performing an update—usually by means of a jumper or switch. Without the lock, any program that knows the correct instructions can rewrite the ROM in your system—not a comforting thought. Without the write-protection, virus programs could be written that overwrite or damage the ROM BIOS code in your system. The CIH virus (also called the Chernobyl virus) was one example that could overwrite the BIOS code on certain motherboards. Instead of a physical write-protect lock, some flash ROM BIOSs have a security algorithm that prevents unauthorized updates. This is the technique Intel uses on its motherboards, eliminating the need for a lock jumper or switch.

Note that motherboard manufacturers do not normally notify you when they upgrade the BIOS for a particular board. You must periodically log on to their websites to check for updates, which you can then download and install at no charge.

Before proceeding with a BIOS upgrade, you must locate and download the updated BIOS from your motherboard manufacturer. Log on to its website, and follow the menus to the BIOS updates page; then select and download the new BIOS for your motherboard.


If a flash BIOS upgrade is identified as being for only certain board revisions of a particular model, be sure you determine that it will work with your motherboard before you install it. You might need to open your system and look for a revision number on the motherboard or for a particular component. Check the vendor’s website for details.

Motherboard manufacturers may offer several ways to update the BIOS on a given motherboard, some may run directly from within Windows, and others may need to be run from bootable removable media such as optical, USB, or floppy. You only need to use one of them, so if you have choices, in most cases you should choose the one that is the easiest to perform. Which one you choose may depend on the current state of the system. For example, if the BIOS is corrupt, you may have no other choice but to use the emergency recovery procedures shown in the next section. If the system you are updating is one you are building for the first time and does not yet have a working copy of Windows installed on the hard drive, you may want to use a method that works with other bootable media such as an optical drive, USB flash drive, or floppy drive. If the update files and programs are too large to fit on a floppy, you should run the update from either an optical drive or a USB flash drive.

Most downloadable flash ROM upgrades fit into five main types:

  • Windows executable upgrades

  • BIOS Setup executable upgrades

  • Automated images of bootable media

  • User-created bootable media

  • Emergency recovery media

The following sections examine each of these in more detail.

Windows Executable Upgrade

The Windows executable method is generally the easiest and most popular. It might not be available for older motherboards, but most new boards offer this type of procedure. Performing the actual upgrade couldn’t be much easier because basically all you have to do is download the executable upgrade program and run it. The program either runs directly in Windows, or it runs an install routine that temporarily installs the flash upgrade software so it automatically runs on the next startup and then automatically reboots the system and begins the upgrade. In either case, once the upgrade is finished, the system reboots again, and the upgrade is complete. The only drawback to this procedure is that it requires that Windows be installed on the system, so it might not be appropriate for new system builds where the OS isn’t installed yet or if you are running an alternative OS, such as Linux.

One potential problem with the Windows executable upgrade method is that if the program runs directly in Windows and the OS is unstable, corrupted, or infected with malware, the BIOS upgrade may be interrupted, potentially requiring a BIOS recovery procedure. Such an event could even destroy the motherboard. Using one of the other methods (such as upgrading from a bootable floppy, CD, or USB flash drive) is preferred if you think the host OS may be unstable.

BIOS Setup Executable Upgrade

Some motherboards now include a flash BIOS upgrade utility in the BIOS. This allows for a BIOS upgrade to be performed in a stable environment outside of Windows, yet without the hassle of having to create DOS-bootable USB flash, optical, or floppy media or entering complicated commands.

This feature is called the F7 BIOS Flash Update on Intel motherboards and M-Flash on MSI motherboards, and it makes the BIOS upgrade procedure simple. To perform the BIOS upgrade, all you need is a FAT- or FAT32-formatted USB flash drive onto which you have downloaded the BIOS image file from the motherboard manufacturer. Unlike previous upgrades via USB flash drives, the drive only needs to contain the BIOS image file and does not need to be bootable or require any other programs to be installed.

To perform the USB flash-based upgrade on a system using an Intel motherboard, first download the proper BIOS image file for the motherboard and copy it to the root folder of a FAT- or FAT32-formatted USB flash drive. Then restart the system, enter the BIOS Setup and navigate to the Advanced, Boot Configuration menu. Make sure the setting Display F7 to Update BIOS is enabled and that it has been saved. Insert the flash drive into a USB port, restart the system, and follow these steps to complete the process:

When prompted during the restart, press F7 to enter the BIOS Flash Update tool.

Select the USB flash drive, and press Enter.

Select the .BIO (BIOS image) file, and press Enter. Confirm that you want to update the BIOS by pressing Enter a second time.

Wait 2–5 minutes for the update to complete; then, when prompted, remove the USB flash drive and restart the system.

To perform the upgrade on a system using an MSI motherboard, first insert the flash drive, restart the system, and then follow these steps to complete the process:

When prompted during the restart, press the Delete key to enter the BIOS Setup.

Select the M-Flash menu, and change the M-Flash function to BIOS Update.

Select the USB flash drive as the source, and point to the BIOS image file on the flash drive.

Select Flash BIOS, and press Enter.

Once the upgrade is finished, the system restarts automatically, after which you can remove the flash drive.

As you can see from these examples, updating a modern motherboard via a BIOS Setup–based utility is almost as easy as using a Windows-based utility, yet it has the advantage of working outside of a Windows environment. In fact, it works even with no OS loaded on the system (and without the hassle of creating DOS-bootable media), which makes it much easier to update the BIOS on a new motherboard or new system build before you install the OS.

Automated Bootable Media Images

Using automated bootable images is the next easiest method and works with any (or no) OS installed on the system. This is ideal for non-Windows systems or new systems in which the OS hasn’t yet been installed. Being able to use this procedure depends on your motherboard manufacturer supplying bootable floppy or optical disc images containing the necessary upgrade files, which you would then use to create the actual upgrade media.

In the case of a floppy, you download the floppy image creation program from the motherboard manufacturer. When you run it, the program prompts you to insert a blank floppy disk into the drive, after which it overwrites the disk with a bootable image containing the bootable OS (most likely DOS or a DOS variant) plus all the files necessary to perform the upgrade. To perform the upgrade, you first ensure that the floppy drive is set in the boot sequence, and then you restart the system with the upgrade floppy disk in the drive. The system should then boot from the floppy, and the upgrade procedure should start and run automatically. Follow any onscreen prompts to complete the upgrade; then when the upgrade is complete, remove the floppy and reboot the system.

Because floppy drives are no longer installed in most newer systems and the BIOS images for newer motherboards are often too large to fit on a floppy anyway, many motherboard manufacturers now offer downloadable images of bootable CDs for BIOS upgrades. These are normally in the form of an *.ISO file, which is an optical disc image file containing a sector-by-sector copy of a disc. To perform the upgrade, you need to write the ISO bootable image file to a blank disc. Unfortunately, Windows versions prior to Windows 7 don’t include optical disc burning software that can read or write ISO images, which means that you need a third-party program to accomplish this. Commercial optical disc burning programs are sometimes included with new systems or optical drives, so you might already have the necessary software on your system. If you don’t already have such a program, I recommend ImgBurn (, which is an excellent free optical disc burning application.

Use your burning program to generate the disc image by copying the ISO file to a blank disc. To perform the upgrade, first ensure that the optical drive is set in the boot sequence; then restart the system with the upgrade disc in the drive. The system should boot from the disc, and the upgrade procedure should start and run automatically. Follow the prompts to complete the upgrade and then, once the upgrade is complete, remove the disc and reboot the system.

User-Created Bootable Media

Many motherboard manufacturers also offer BIOS upgrades in the form of a raw DOS-based flash utility combined with a BIOS image file, which you can run manually from any DOS-bootable media. Using this technique, you can perform the upgrade from a bootable floppy, optical disc, or even a USB flash drive, regardless of whether the system hard drive is running Windows or Linux or even if it has no OS. The necessary files are normally contained in an archive that you can download from the motherboard manufacturer. Unfortunately, this type of procedure is much more labor intensive than the others because several steps are involved. One particularly difficult part is the manual creation of the bootable media to which you will copy the files. Although it is fairly straightforward and simple to create a bootable floppy, the procedure for creating bootable optical discs or USB flash drives is more involved.

Fortunately, some free utilities are helpful. For creating a bootable CD for BIOS upgrades, I recommend the Clean Boot CD package, which you can download for free from Download the self-extracting executable package into a new folder and run it, which extracts the additional files and folders within. Then follow the directions to copy the flash utility and image files for your motherboard into the proper folder. After the files are in place, you can run the “build-clean” command, which automatically builds and creates an ISO image of a bootable CD, complete with an OS and your files included. You can then use a third-party CD/DVD-burning program such as ImgBurn ( to copy the ISO image to an optical disc.

After you have burned the disc, you can boot from it, navigate to the folder where your flash utility and image files are located, and enter the appropriate command to execute the upgrade. For Intel motherboards that use the IFLASH.EXE utility and image files with an *.BIO extension, the proper command would be IFLASH /PF XXX.BIO, where you would replace XXX.BIO with the actual name of the BIO file you have.

You can accomplish the same procedure with a bootable USB flash drive, but just as with the creation of a bootable optical disc, creating a bootable USB flash drive can be somewhat involved. Fortunately, a Windows-based USB format utility (HPUSBDisk.exe) is available for free from HP ( To make the flash drive bootable, this program requires a set of DOS system files (, io.sys, and msdos.sys) to write to the flash drive during the format. You can use several versions of DOS, but in most cases I recommend using the system files from DOS 6.22. If you don’t have a copy, you can download the DOS 6.22 system files in the form of a bootable floppy image Look for the “Non-Windows Based Image Files,” and then download the file. Use a program like 7-Zip ( to first extract the .IMG file from the zip file, and then use it again to extract the DOS files from the .IMG file.

To create the bootable flash drive, run the HPUSBDisk.exe program and select the flash device and file system (FAT). Then check Create a DOS Startup Disk Using System Files Located At and point to the location where you have extracted the necessary DOS files. After that, perform the format.


BIOS and motherboard manufacturers began adding USB boot support during 2001, so if your system dates from around that time or earlier, it might not be able to boot from a USB drive.

When setting up a system to boot from a USB flash drive, the flash drive must be plugged in prior to restarting the system and entering the BIOS setup. In the BIOS setup startup sequence (boot order), the USB flash drive might appear as either a “generic” storage device hard disk or as a type of removable drive, which you should set as the first device in the boot order. In most systems, when the USB flash drive is unplugged, it is automatically removed from the boot order on the next restart.

After the USB flash drive is formatted as a bootable drive, you can add the BIOS flash utility and image file for the motherboard. Plug the bootable USB flash drive into the system you want to upgrade, and then restart the system, run the BIOS setup, and set the USB flash drive to be first in the boot sequence. After you save and exit, the system should boot to DOS from the USB flash drive. At the DOS command prompt, you can then run the proper command to reflash your BIOS.


Before you start the flash BIOS upgrade process, you should disconnect all USB and IEEE 1394 (FireWire) devices except for your keyboard and mouse. If you are booting from a USB flash drive to perform the upgrade, make sure all other USB drives are disconnected. On some systems, leaving additional external drives connected prevents a BIOS upgrade from working properly.

If you have Byte Merge enabled in the BIOS Setup on an Award BIOS-based system, disable this feature as a precaution before you perform the BIOS upgrade. This is recommended because on some older systems, leaving Byte Merge enabled during a BIOS upgrade can cause the upgrade to fail, corrupting the BIOS in the process. You can reenable this feature after you complete the upgrade. Some BIOS upgrades contain fixes for this problem so it can’t happen in the future.

Emergency Flash BIOS Recovery

When you perform a flash BIOS upgrade, you should normally see a warning message onscreen similar to the following:

The BIOS is currently being updated. DO NOT REBOOT OR POWER DOWN until the update is completed (typically within three minutes)...

If you fail to heed this warning or something interrupts the update procedure, you can be left with a system that has a corrupted BIOS. This means you will not be able to restart the system and redo the procedure, at least not easily. Depending on the motherboard, you might have to replace the flash ROM chip with one that was preprogrammed by the motherboard manufacturer. This is an unfortunate necessity because a motherboard is nonfunctional until a valid ROM is present. This is one reason I still keep my trusty ROM burner around; it is useful for motherboards with socketed flash ROM chips. In minutes, I can use the ROM burner to reprogram the chip and reinstall it in the board. If you need a ROM programmer, I recommend the EPROM+ from Andromeda Research Labs (

In most systems, however, the flash ROM is soldered into the motherboard so it can’t be easily replaced, rendering the external reprogramming idea moot. However, this doesn’t mean the only way out is a complete motherboard replacement. Most motherboards with soldered-in flash ROMs have a special BIOS Recovery procedure that can be performed, which restores the contents of the chip. This hinges on a special protected part of the flash ROM that is reserved for this purpose, called the boot block. The boot block holds a recovery routine that you can use to restore the main BIOS code.


Because of the small amount of code in the boot block area, onscreen prompts are not usually available to direct the procedure. This means that during the procedure the screen remains dark—as if nothing is happening. The procedure can instead be monitored by listening to the internal speaker or looking at the access LED on the drive containing the upgrade media. Normally the procedure causes the system to beep once when it begins and several more times when it ends. During the procedure, you should be able to observe drive activity, indicating that the BIOS image is being read from the drive and written into the flash device.

Different motherboards and BIOS versions may have different recovery techniques. Most motherboards (including those from Intel) that support BIOS recover incorporate a BIOS configuration jumper, which can set several modes, including a built-in recovery mode. Figure 5.7 shows this jumper on a typical motherboard.

Figure 5.7. BIOS configuration jumper.

In addition to moving the jumper, the recovery requires that either a floppy, optical, or USB flash drive containing media with the BIOS image file is attached to the system and properly configured. Most older motherboards only support recovery from a floppy drive, whereas most newer boards support optical or USB.

Before beginning the recovery procedure, you need to download the proper recovery image file for the motherboard you are recovering. Obviously, you need to do this using another system if the system to be recovered is nonfunctional. The image file can be downloadable separately, or it can be part of an archive with other files, such as flash programming tools and documentation. In this case you only need the actual image file; none of the other programs or files will be used. You also need to ensure that either a working floppy or optical drive is properly installed in the system.

To recover the BIOS using the floppy recovery method, perform the following steps:

Copy only the proper recovery image file to a blank formatted floppy disk.
Place the disk in the primary floppy drive attached to the system to be recovered.
Power off the system and remove the BIOS configuration jumper to enable BIOS Recovery mode (refer to Figure 5.7).
Power on the system; the recovery should begin automatically. You should hear a beep at the start and see activity on the floppy drive during the procedure.
The recovery should complete in 2 to 5 minutes, after which the system will remain running, power off automatically, or prompt you to turn it off manually.
With the system powered off, remove the floppy disk, and restore the BIOS configuration jumper to enable normal operation.

You can use the optical or USB flash drive methods on newer motherboards that do not have a built-in floppy controller or for which the recovery file won’t fit on a 1.44MB floppy. Although the drive can be virtually any type of CD or DVD optical drive, the actual disc you use should be a CD-R or RW that is burned with the file and finalized (closed). You can burn the disc using the built-in CD-burning software found in Windows (XP or later), or you can use third-party software such as the free ImgBurn application (, which is more powerful, easier to use, and works with older versions of Windows.

To recover the BIOS using the optical drive method, perform the following steps:

Burn and finalize a disc (preferably a CD) with a copy of the recovery image file.
Place the disc in the primary optical drive of the system to be recovered.
Power off the system and remove the BIOS configuration jumper to enable BIOS Recovery mode.
Power on the system; the recovery should begin automatically.
The recovery should complete in 2 to 5 minutes, after which the system will remain running, turn off automatically, or prompt you to turn it off manually.
With the system powered off, restore the BIOS configuration jumper to enable normal operation.


A BIOS recovery may corrupt the BIOS Setup information stored in the CMOS RAM. If the error message CMOS/GPNV Checksum Bad...Press F1 to Run SETUP appears during the first boot after the update, press F1 to go into the BIOS Setup Utility, press F9 to load setup defaults, and then press F10 to save and exit to correct the problem.

If your motherboard does not include a BIOS configuration jumper, there might still be a recovery procedure that could work. For example, some AMI BIOSs have boot block code with a recovery procedure that works even without a recovery jumper. If the main BIOS is damaged, the boot block code is designed to look for a file called AMIBOOT.ROM on a floppy disk and flash it into the ROM if found. To perform a recovery, first download the latest BIOS image file for the motherboard, copy the file to a blank formatted floppy, and then rename the image file to AMIBOOT.ROM. Power off the system to be recovered, insert the floppy, and then power on; the recovery process should start automatically.

Most Phoenix and Award BIOSs also have a boot block with recovery capabilities. These are designed to automatically boot from a floppy disk if the main BIOS is damaged. To perform a recovery, first download the latest BIOS upgrade files for the motherboard. Extract the files and copy the Award flash program (awdflash.exe) and the correct BIOS image (*.bin) file to a bootable formatted floppy, and then create an AUTOEXEC.BAT file on the floppy with the command awdflash.exe *.bin, replacing the *.bin with the actual name of the BIOS image file for the specific motherboard being recovered. Power off the system to be recovered, insert the floppy, and then power on. The system should boot from the floppy, and the recovery process should start automatically.

With any of these procedures, wait at least several minutes after all disk and beeping activity stops before removing the floppy or CD and restarting the system. When you power the system back on, the new BIOS should be installed and functional. If nothing at all happens, the recovery may have failed, or the board may not feature a separate boot-block section (which contains the recovery code).


Note that the BIOS recovery procedure is often the fastest way to update a large number of machines, especially if you are performing other upgrades at the same time, or the machines are new and do not have a bootable OS installed. For example, this is how updates are sometimes done in a system assembly or production environment.

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Motherboard CMOS RAM Addresses
In the original IBM AT system, a Motorola 146818 chip was used as the real-time clock (RTC) and CMOS RAM chip. This special chip had a simple digital clock that used 14 bytes of RAM and an additional 50 more bytes of leftover RAM in which you could store anything you wanted. The designers of the IBM AT used these extra 50 bytes to store the system configuration.

Modern PC systems don’t use the Motorola chip; instead, they incorporate the functions of this chip into the motherboard chipset (South Bridge) or Super I/O chip, or they use a special battery and NVRAM module from companies such as Dallas Semiconductor or Benchmarq.

Table 5.1 shows the standard format of the information stored in the 64-byte standard CMOS RAM module. This information controls the configuration of the system and is read and written by the system setup program.

Table 5.1. CMOS RAM Addresses
Offset (hex) Offset (dec) Field Size Function
00h 0 1 byte Current second in BCD[1] (00–59)
01h 1 1 byte Alarm second in BCD
02h 2 1 byte Current minute in BCD (00–59)
03h 3 1 byte Alarm minute in BCD
04h 4 1 byte Current hour in BCD (00–23)
05h 5 1 byte Alarm hour in BCD
06h 6 1 byte Current day of week in BCD (00–06)
07h 7 1 byte Current day of month in BCD (00–31)
08h 8 1 byte Current month in BCD (00–12)
09h 9 1 byte Current year in BCD (00–99)
0Ah 10 1 byte Status register A
0Bh 11 1 byte Status register B
0Ch 12 1 byte Status register C
0Dh 13 1 byte Status register D
0Eh 14 1 byte Diagnostic status
0Fh 15 1 byte Shutdown code
10h 16 1 byte Floppy drive types
11h 17 1 byte Advanced BIOS Setup options
12h 18 1 byte Hard disk 0/1 types (0–15)
13h 19 1 byte Keyboard typematic rate and delay
14h 20 1 byte Installed equipment
15h 21 1 byte Base memory in 1K multiples, LSB[2]
16h 22 1 byte Base memory in 1K multiples, MSB[3]
17h 23 1 byte Extended memory in 1K multiples, LSB
18h 24 1 byte Extended memory in 1K multiples, MSB
19h 25 1 byte Hard Disk 0 Extended Type (0–255)
1Ah 26 1 byte Hard Disk 1 Extended Type (0–255)
1Bh 27 9 bytes Hard Disk 0 user-defined type information
24h 36 9 bytes Hard Disk 1 user-defined type information
2Dh 45 1 byte Advanced BIOS Setup options
2Eh 46 1 byte CMOS checksum MSB
2Fh 47 1 byte CMOS checksum LSB
30h 48 1 byte POST[4] reported extended memory LSB
31h 49 1 byte POST reported extended memory MSB
32h 50 1 byte Date century in BCD (00–99)
33h 51 1 byte POST information flag
34h 52 2 bytes Advanced BIOS Setup options
36h 54 1 byte Chipset-specific BIOS Setup options
37h 55 7 bytes Power-On Password (usually encrypted)
3Eh 62 1 byte Extended CMOS checksum MSB

[1] BCD = Binary-coded decimal

[2] LSB = Least significant byte

[3] MSB = Most significant byte

[4] POST = Power-on self test

Note that many newer systems have extended CMOS RAM with 2KB, 4KB, or more. The extra room stores the Plug and Play information detailing the configuration of adapter cards and other options in the system. As such, no 100%-compatible standard exists for the way CMOS information is stored in all systems. You should consult the BIOS manufacturer for more information if you want the full details of how CMOS is stored because the CMOS configuration and setup programs typically are part of the BIOS. This is another example of how close the relationship is between the BIOS and the motherboard hardware.

Backup programs and utilities are available in the public domain for CMOS RAM information, which can be useful for saving and later restoring a configuration. Unfortunately, these programs are BIOS specific and function only on the BIOS for which they are designed. As such, I don’t usually rely on these programs because they are too motherboard and BIOS specific and do not work on all my systems seamlessly.

Table 5.2 shows the values that might be stored by your system BIOS in a special CMOS byte called the diagnostic status byte. By examining this location with a diagnostics program, you can determine whether your system has set trouble codes, which indicate that a problem previously has occurred.

Table 5.2. CMOS RAM Diagnostic Status Byte Codes
Bit Number
7 6 5 4 3 2 1 0 Hex Function
1 80 Real-time clock (RTC) chip lost power.
1 40 CMOS RAM checksum is bad.
1 20 Invalid configuration information found at POST.
1 10 Memory size compare error at POST.
1 08 Fixed disk or adapter failed initialization.
1 04 Real-time clock (RTC) time found invalid.
1 02 Adapters do not match configuration.
1 01 Timeout reading an adapter ID.

If the diagnostic status byte is any value other than 0, you typically get a CMOS configuration error on bootup. You can clear these types of errors by rerunning the setup program.

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Year 2000 BIOS Issues
All systems now in use should be compliant with twenty-first century dates, either through BIOS updates or through software or hardware patches. However, if you are returning to service stored systems built before 1999, you might want to test them for year-2000 compliance.

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