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Intel Motherboards:

BIOS Flashing FAQ

V. 0.02

Updated June 26, 2002

This document is an "in-development" FAQ provided as a reference only. Contributors to this document are welcome to add or modify it as they wish as long as the modified document is sent to me for updating. You can send your suggestions and/or modified document to biosflashingfaq (at) setiri (dot) com.

ATTENTION: Flashing the system BIOS or any other BIOS for that matter is a dangerous operation. Performing a flash can render the system inoperable. Any modifications done to a BIOS with or without the aid of this document is completely up to the user. Neither I, the author, nor any other person contributing to this document can be held accountable for any loss of data, or failure of any flash procedure done.



What is the BIOS and how does it work?


Inside every PC out there is BIOS, which stands for Basic Input Output System.  In a nutshell, BIOS is software that interacts between a computers hardware and the operating system and software applications.  There are several types of BIOS's, ranging from the motherboard ROM BIOS to adapter BIOS's such as video BIOS, drive controller BIOS, network adapter BIOS, SCSI adapter BIOS, etc... These BIOS's are the lowest level of software in a computer providing a set of small programs or software routines that allow the hardware of a computer to interact with the operating system by a set of standard calls.

I hope to provide a through understanding of how the BIOS works and leave you with a better understanding of it's interworkings. At the same time, I hope to show how complex a BIOS is in relation to it's relationship with the operating system and the software applications you use everyday. Enjoy.

The Boot Process

To get to the operating system, a computer must first boot from the BIOS.  The BIOS performs a number of tasks when a computer is started.  From initializing the microprocessor to initializing and testing hardware to starting the operating system.  Starting a computer is not a simple task.  It's a methodical process that is performed every time power is applied to computer.  Here is a detailed description of the boot process.  This process will vary with different computers and different BIOS', but the overall goal is the same. When you first turn on a computer the very first operation performed by the CPU is to read the address space at FFFF:0000h. This address space it reads from is only 16 bytes, which is not nearly enough space to house the BIOS found on a motherboard.  Instead, this location contains a special instruction called a jump command (JMP) that tells the processor where to go to find and read the actual BIOS into memory.  The process of the processor reading the jump instruction and redirection to the actual BIOS is called the bootstrap or boot. So, when you apply power, it's not the operating system that's working. It's the BIOS.

First, I want to get something straight.  The CMOS and the BIOS are two different things.  The BIOS refers to the firmware instructions that are located on the BIOS ROM.  CMOS refers to the low-power RAM that holds the system's setup parameters.  The BIOS reads the CMOS RAM into memory at boot up and provides the setup routine that allows you to change the contents of CMOS, but the CMOS RAM/RTC device is a totally different IC.  The CMOS holds the information provided by the BIOS.  This is why you "lose" the settings of a system when the battery dies or you clear the CMOS through a jumper on the motherboard.

With today's high performance 32 bit operating systems, the BIOS becomes less used, but it is still there, always interacting with the operating system. Disk access, for example, is done through the operating system with 32-bit routines, whereas the BIOS is using 16-bit routines. Although the BIOS provides VGA support, Windows and other 32-bit operating systems use software device drivers to work with the hardware.  Early OS's, like DOS, worked with the BIOS.  DOS relied on the BIOS to perform most functions, like displaying characters on the screen or sending output to the printer, reading input from the keyboard and other essential tasks. These drivers, which operate in protected mode(since they aren't written for real mode, they are able to use memory above the 1MB barrier that real mode provides), allow for several enhancements.   They can access more memory, can be written in 32-bit code for optimized execution and are not limited to the amount of space available to their code. However, regardless of OS, whether it's Windows 2000, Linux or DOS, the BIOS and the operating system still interact with each other.

Here is a basic rundown of what is happening:

   1.  Power is applied to the computer

   When power is applied to the system and all output voltages from the power supply are good, the power supply will generate a power good signal which is received by the motherboard timer.  When the timer receives this signal, it stops forcing a reset signal to the CPU and the CPU begins processing instructions.

    2.  Actual boot

    The very first instruction performed by a CPU is to read the contents of a specific memory address that is preprogrammed into the CPU.  In the case of x86 based processors, this address is FFFF:0000h.   This is the last 16 bytes of memory at the end of the first megabyte of memory.   The code that the processor reads is actually a jump command (JMP) telling the processor where to go in memory to read the BIOS ROM.  This process is traditionally referred to as the bootstrap, but now commonly referred to as boot and has been broadened to include the entire initialization process from applying power to the final stages of loading the operating system.

   3.  POST

    POST stands for Power On Self Test.  It's a series of individual functions or routines that perform various initialization and tests of the computers hardware.  BIOS starts with a series of tests of the motherboard hardware.  The CPU, math coprocessor, timer IC's, DMA controllers, and IRQ controllers. The order in which these tests are performed varies from motherboard to motherboard. Next, the BIOS will look for the presence of video ROM between memory locations C000:000h and C780:000h.  If a video BIOS is found, It's contents will be tested with a checksum test.  If this test is successful, the BIOS will initialize the video adapter. It will pass controller to the video BIOS, which will in turn initialize itself and then assume controller once it's complete.  At this point, you should see things like a manufacturers logo from the video card manufacturer video card description or the video card BIOS information.  Next, the BIOS will scan memory from C800:000h to DF800:000h in 2KB increments.  It's searching for any other ROM's that might be installed in the computer, such as network adapter cards or SCSI adapter cards. If a adapter ROM is found, it's contents are tested with a checksum test.  If the tests pass, the card is initialized. Controller will be passed to each ROM for initialization then the system BIOS will resume controller after each BIOS found is done initializing. If these tests fail, you should see a error message displayed telling you "XXXX ROM Error".  The XXXX indicates the segment address where the faulty ROM was detected.  Next, BIOS will begin checking memory at 0000:0472h.  This address contains a flag which will tell the BIOS if the system is booting from a cold boot or warm boot.  A value of 1234h at this address tells the BIOS that the system was started from a warm boot. This signature value appears in Intel little endian format , that is, the least significant byte comes first, they appear in memory as the sequence 3412. In the event of a warm boot, the BIOS will will skip the POST routines remaining.  If a cold start is indicated, the remaining POST routines will be run.  During the POST test, a single hexadecimal code will be written to port 80h.  Some other PC's send these codes to other ports however. Compaq sends them to port 84h, IBM PS/2 model 25 and 30 send them to port 90h, model 20-286 send them to port 190h. Some EISA machines with an Award BIOS send them to port 300h and system with the MCA architecture send them to port 680h. Some early AT&T, Olivetti, NCR and other AT Clones send them to the printer port at 3BC, 278h or 378h. This code will signify what is being tested at any given moment.   Typically, when the BIOS fails at some point, this code will tell you what is failing. 

   4.  Looking for the Operating System

    Once POST is complete and no errors found, the BIOS will begin searching for an operating system.   Typically, the BIOS will look for a DOS Volume Boot Sector on the floppy drive.   If no operating system is found, it will search the next location, the hard drive C.  If the floppy drive (A), has a bootable floppy in it, the BIOS will load sector 1, head 0, cylinder 0 from the disk into memory starting at location 0000:7C00h.  The first program to load will be IO.SYS, then MSDOS.SYS.  If the floppy does not contain a DOS volume boot sector, then BIOS will next search the computers hard drive for a master partition boot sector and load it into memory at 0000:7C00h.  There are some occasions in which you will encounter problems with the proper loading of the Volume Boot Sector.  Below are some of those:

            A.  If the first byte of the Volume Boot Sector is less than 6h, then you will receive a message similar to "Diskette boot record error".

            B.  If the IO.SYS or MSDOS.SYS are not the first two files in the Volume Boot Sector, then you will see a message similar to "Non-system disk or disk error".

            C.  If the Volume Boot Sector is corrupt or missing, you will get a message similar to "Disk boot failure"

Once the BIOS has searched for a bootable floppy device, it should turn it's attention to the next boot device it's programmed to look for.  The next device is typically the hard drive, or C.   Like a floppy drive, the BIOS will attempt to load the Volume Boot Sector from sector 1, head 0, cylinder 0 from the Master Boot Sector, or MBS, into memory starting at 0000:7C00h.  The BIOS will check the last two bytes of the MBS.  They should be 55h and AAh respectively.  If they are not, then you will receive an error message similar to "No boot device available" and "System initialization will halt".  If they are correct, then the BIOS will continue the loading process.   At this point, the BIOS will scan the MBR in search of any extended partitions.   If any extended partitions are identified, the original boot sector will search for a boot indicator byte which indicates a active and bootable partition.  If it cannot find one, you will receive a message similar to "Invalid partition table".

At this, once a active partition is found, the BIOS will search for a Volume Boot Sector on the bootable partition and load the VBS into memory and test it.  If the VBS is not readable or corrupt, you will see a message similar to "Error loading operating system".  At the point, the BIOS will read the last two bytes of the VBS.  These bytes should be 55h and AAh respectively.  If they are not, then you will see a message similar to "Missing operating system"  It is at this point that the BIOS will begin loading of the operating system.

What should I do to prepare for flashing my BIOS?

Backup your system current BIOS. Installing a new BIOS may introduce bugs into the system that may create new system issues. Things like memory timing, CPU speed indicaters, fan speed and power management issues as well. With both AMI and Award, the utility has the ability to backup the current BIOS onto a floppy disk. It's highly recommended that anyone performing a BIOS update perform this. If you have a printer connected to the system you can print each setup screen within the BIOS by using the "PrtScn" key on the keyboard. This will give you a hard copy to check your settings against after the flash takes place.

Make sure you have the correct BIOS upgrade. If you have an upgrade for another motherboard, even if the motherboard is in the same series, just a different model, chances are pretty good you'll render the motherboard unusable. ONLY UPGRADE A BIOS WITH A NEWER BIOS THAT IS DESIGNED FOR THE SPECIFIC MOTHERBOARD IN QUESTION!

Make sure you have a thoroughly tested floppy disk AND drive in place before using them to flash the BIOS. In the event of a CRC error during the flash, you will most likely have to replace the CMOS. A costly operation in terms of money and downtime. If anything goes wrong with the disk or the drive during the flash, it will most likely toast your motherboard. Ensure that the drive your using and the floppy disk itself are up to snuff. Test the disk thoroughly. Write and read from it with large files. Perform a complete format of the disk as well. If any bad sectors occur, replace the disk with another. DON'T USE THE FLOPPY DISK IF ERRORS ARE FOUND ON IT!

When booting the system to the floppy for flashing, ensure that the boot floppy itself has NO unneeded drivers being installed. Things like CD-ROM drivers or mouse drivers will reduce the amount of memory available for the flashing program to use. If you run out of RAM during the flashing, your motherboard may be rendered unusable. Always boot with boot disk that has no additional drivers. After all, all you need is the floppy anyway. Enter the BIOS setup and ensure that system and video BIOS caching is disabled and all types of Shadow Memory are disabled.

How do I flash a BIOS?

Flashing your motherboards BIOS a fairly straight forward procedure. The required components are the proper flashing utility and the proper data file that will be written the CMOS. To accomplish this, your first stop is the web site of your motherboard manufacturer and download the latest flashing utility and BIOS update. There are other places to download the flashing utilities, however, I recommend using the utility that comes with your latest bin file or the one recommended by your motherboard manufacturer. With some motherboards, the individual motherboard manufacturer uses their own proprietary flashing utility. Make sure you always check your motherboard manufacturer's website for any information and read the motherboard manual to find any information related to this.

Ensure your using a newer floppy disk and that your floppy drive is not causing any problems. If your floppy drive is questionable, then replace it before performing the upgrade. One bad CRC error during the flashing of the BIOS and it's toast. As for the floppy, I highly recommend using a brand new one or at least a nearly brand new one. Perform a complete format of the disk before using it to ensure no problems are found with it. I also suggest that you don't use a floppy disk that has any bad sectors or other problems with it.

Before flashing any BIOS you should prepare the system for flashing. If your computer is overclocked it is highly recommended that you set the CPU to run at the default speed. Enter the BIOS setup and disable all forms of shadowing. This includes, Video BIOS Cacheable and System BIOS Cacheable, which can be found within the Chipset Features Setup. You should also disable any power management features that are enabled. If you system has a setting within the BIOS to protect the BIOS from flashing you will need to disable this as well. Some motherboard have a jumper on them that can be set to protect the BIOS from being flashed. This needs to be disabled as well if it is present.

For Award BIOS's:

For Award BIOS's, the flashing procedure is fairly simple. It can be a little intimidating for those who are unfamiliar to the command line though. Rest assured, it's really not all that hard. After you have downloaded the latest BIOS and the flashing utility, place those files on a floppy disk. You will want to have them either on a floppy disk that is bootable or on a floppy disk separate from the boot disk. In either case, your going to need a boot disk to perform the flashing. To create a boot disk, insert a black floppy disk into the drive. If your using Windows 9x, open My Computer and right click on the A: drive. Select Format and ensure that the create system disk is checked. For Windows 2000 users, your going to need a bootable disk created elsewhere. Windows XP users can create a bootable floppy using the same method as Windows 9x users. This creates a Windows ME boot disk. Once you have a boot disk created and a copy of the flashing utility and a copy of the latest BIOS update, your ready to flash the BIOS.

Boot to the bootable floppy. Once you have booted the system to the command line ensure that the floppy disk containing the flashing utility and the BIOS update is in the drive. The next portion will vary from system to system. The flashing utility and the BIOS update image will vary so the following is a general guideline to working with the command line:


(a listing of the files located on a: drive will be displayed)A:\>awdflash b1sv13.bin

A:\>awdflash b1sv13.bin

(Runs the Award flashing utility and directs it to the BIOS update file )

Follow the onscreen instructions for the flashing procedure. A word of caution at this point. DO NOT pull the plug, press the reset button or otherwise interrupt the flashing procedure once it has begun. Interruption of the flashing procedure WILL render the system unbootable!

A method of flashing an Award BIOS is to automate it. By creating a prepared bootdisk with the flashing utility and the BIOS .bin file on it, you can create a bootable disk that will flash the BIOS and perform other functions for you without having you type anything. After you have created a bootable floppy, using you favorite text editor, open the autoexec.bat file located on the floppy disk. If one is not present then just save the file once you have created it to the floppy as autoexec.bat. The following code will completely automate the flashing procedure for you:

@echo off
if exist oldbios.bin goto old
awdflash.exe newbios.bin oldbios.bin /py /sy /cc /cp /cd /sb /r
goto end
awdflash.exe oldbios.bin /py /sn /cc /cp /cd /sb /r

The awdflash.exe is the name of the flashing program you are using. The newbios.bin is the name of the bios image you downloaded for you motherboard. The oldbios.bin file is the name of the bios you choose to save the old bios (your current BIOS) onto floppy as. IF your BIOS flash fails, the old BIOS is in backed up in oldbios.bin. You can just reboot with that floppy again and the process of flashing the bios to the old version is automatic. As long as the oldbios.bin is present on the floppy, it will get flashed to the BIOS. After flashing the BIOS to a newer version remember to remove the floppy from the drive. The process of flashing the BIOS is automatic, so if you leave the floppy in the drive it will flash the BIOS again.

The following are the command line switches for the Award flashing utility. You can use these in conjunction with the flashing utility to help automate the flashing procedure. For example:

AWDFLASH xxxx.BIN /py/sn/cc

Would run the flashing utility and tell the utility to perform the flash (/py), do not save the current BIOS into a backup file (/sn), and clear the CMOS after performing the flash (/cc). After flashing any BIOS, either Award, AMI, Phoenix, or any other motherboard BIOS, always clear the CMOS. The values that are current saved in the CMOS may not match the setup programs new procedures. If the BIOS update installed any new instructions or set up new values for any existing procedures, these values won't match what is expected. For this reason, you should ALWAYS clear the BIOS after flashing it and reconfigure the BIOS after clearing it.

/? - Help. Before you start working with Award Flash Memory Writer, it is advisable to use this key and to study carefully all the opportunities of this software.

/Py or /Pn - stands for answering "yes" (Y) or "no" (N) to the request concerning the BIOS reflashing. By means of /Pn you can ban FlashROM reprogramming. This option enables you to save the current version of the BIOS or to get its checksum without updating your BIOS. A backup copy will help you to restore the previous version of the BIOS. By default /Py mode is set.

/Sy or /Sn - stands for answering "yes" (Y) or "no" (N) to the request about saving the previous version of the BIOS. By default /Py mode is set again. In this case before reprogramming the FlashROM microchip you'll need to confirm saving by this request:

Do You Want To Save BIOS (Y/N)

/Sn is recommended to use for *.bat-files in case of automatic BIOS reflashing in systems without a display.

/CC - to clear CMOS after reflashing. This option comes in handy when there is a risk that the data arrays created by new BIOS version in CMOS may differ from those former ones. If so, then you are likely to have troubles with the mainboard startup. Clearing CMOS will let you avoid searching for Clear CMOS jumper on the board, which is really helpful if it isn't accompanied with a proper manual or is simply hard to access.

/CP - stands for clearing PnP (ESCD) Data matrix after BIOS reflashing. The information about PnP devices is stored in ESCD. The key /CP is an equivalent to Reset Configuration Data in PnP/PCI Configuration CMOS Setup. It makes sense to use /CP if you skip several versions of BIOS or if you have installed new PnP cards. If you don not update the ESCD, your board may suffer some startup problems.

/CD - stands for clearing DMI Data pool after reprogramming. Literally, DMI is a data base, containing all the information on the system as a whole. Clearing it may be fruitful in the above mentioned situations with /CP and /CC keys, as well as if some of the system components have been changed.

/SB - stands for no BootBlock reflashing. The BootBlock is the first unit to be addressed by startup and it is hardly ever changed. If the board manufacturer gives no other recommendations, there is no need to reflash BootBlock. In particular, if the BIOS reflashing fails, it may become impossible to restore the BIOS via software. On some mainboards there is a BootBlock Protection jumper. If protection is set, either you won't be able to reflash the BIOS without /SB at all or the system will face verification errors.

  • This setting has NOT been confirmed to work. It may or may not work on your motherboard. Use with caution. Thanks for the input Tmod.

/SD - stands for saving the data of DMI pool in a file. Part of DMI can be saved to be used by the software in future. Even though this key stands in the list, which is shown by /?, using it will bring no result. This key simply doesn't work.

/R - stands for the system reset after reflashing. It lets you have your computer restarted automatically as soon as you finish updating FlashROM. The option is useful for working through a *.bat-file.

/Tiny - stands for using less RAM. Without the /Tiny key, AwardFlash utility tries to put the entire BIOS file, which is intended for further reflashing, into RAM. Still, if have taken all the precautions but anyway you see a message saying "Insufficient Memory" during the BIOS reflashing procedure, then the key /Tiny should be used. It will make the data from the BIOS file loaded and reflashed in portions.

/E - stands for returning to DOS after BIOS reflashing. For instance, you may need it to make sure that the previous version of the BIOS is saved.

/F - stands for reprogramming by means of the system BIOS. Most contemporary BIOS's feature the procedure of FlashROM reprogramming. The key /F enables AwardFlash to reprogram FlashROM with the algorithms of the current BIOS version. If a mainboard peculiarities do not allow applying AwardFlash Writer algorithms, you should use the key /F.

/LD - stands for clearing CMOS after reflashing and not showing the message "Press F1 to continue or DEL to setup". Unlike /CC, this key lets you avoid this message by the following startup after clearing CMOS, provided you have set the properties by default.

/CKS - stands for showing the checksum of XXXXh file. The checksum is shown in hexadecimal representation. This option is advised to be used with the verification key.

/CKSxxxx - stands for comparing the checksum of the file with XXXXh. If the checksums are different, you'll see the message "The program file's part number does not match with your system!". As a rule, XXXXh for each BIOS update file is usually available on the mainboard manufacturer's site

/WB - Updates the BIOS Boot Block. This switch does not have to be used. The BIOS Boot Block will get updated with the flashing of the BIOS.

  • Thanks for the input Tmod

/CC = clear cmos data after programming

/CD = clear dmi data after programming

/CP = clear PnP (ESCD) data after programming

/R = reset system after programming

/PY = program flash memory

Here are some additional command line switches for the Award flashing program:

/? = show help menu

/SY = backup original BIOS to disk

/SB = skip bootblock programming

/TINY = occupy lesser memory

/E = return to DOS when programming is done

/F = use flash routines in original BIOS for flash programming

/LD = destroy cmos checksum and no system halt for first reboot after programming

/CKSxxxx = compare binfile checksum with xxxx

/CKS = show update binfile checksum

/PN = no flash programming

/SN = no original BIOS backup

/SD = save dmi data to file

/WB = flashes the BIOS Boot Block


Why should I update the BIOS? When should I upgrade my BIOS [when is it really necessary, when is it just for "fun"]

Flashing a BIOS can be destructive to the motherboard. Without a BIOS that is in proper working condition, your computer will simply not work. The BIOS is actually what is used to start your PC up, thus is a very important component to the operation of any PC. Unless you are sure that your system requires an update and that the update is going to fix any problem that you're experiencing, then I would not recommend flashing the BIOS. Remember, if the flash fails, then your system is NOT going to work. Further repair will be required which could require monetary means to repair.

One thing I try to tell people who are interested in doing flashing and/or doing BIOS modifications is to pick up a few older motherboards at a local flea market or 2nd hand store. Some place where you find some cheap used parts you don't mind losing. This is a great way to learn/practice doing advanced things like BIOS Moding without the worry of screwing up the new motherboard in your main system. I would much rather lose a $10 board than a $200 one. The salvation Army, Goodwill, or other second hand stores, as well as the local hospice. I once found a Pentium 120MHz with mainboard and 128MB of RAM still on it at a local hospice for $10 bucks. A deal and a half. At the time the top of the line systems were PII 400's.

When I boot the BIOS all it says is "BIOS checksum error, press F1 to continue...". What should I do?

This is a result of the CMOS losing the data that it was holding. There are a few ways that this can be encountered. After flashing a BIOS, loss of battery power, an electrical surge or bad power to name a few. Typically, this is a problem with the CMOS battery running low. The result is usually discovered after the system has been off for a few hours or longer. Replace the battery located on the motherboard:

If you just performed a flashing of the BIOS, use the jumper on the motherboard to clear the CMOS. You can also enter the BIOS and choose "Load BIOS Defaults".

How do I clear the CMOS?

Clearing the CMOS can be done a few ways. The most common way is to use the jumper on the motherboard. This jumper has two settings. Normal and Clear. Moving the jumper to the Clear setting will erase the settings stored in CMOS. It does not remove the BIOS itself, only the user defined settings within the CMOS. When you clear the CMOS you will most likely see the error message "CMOS Checksum Error" on the next reboot. You can enter the BIOS setup at this point or before and reconfigure the settings.

Another method is to remove the CMOS battery from the system. Removing the battery is usually the second method as it may take anywhere from 15 minutes to 8 hours in order for the CMOS to loss the settings. Once the CMOS is clear, you should know by the "BIOS checksum error, press F1 to continue ", or "CMOS Checksum Error - Defaults Loaded" message at bootup.

You may also be able to clear the CMOS in some cases by forcing a system configuration change. Changing hardware, such as adding or removing a few SIMM's may cause a CMOS error and allow you to proceed to the BIOS setup.

On a few systems it may be possible to clear the CMOS by pressing the Ins key during the power up of the system. Holding the Key down may clear the CMOS and restore the defaults. This may or may not work on your system.

How do I get a replacement BIOS chip? How can I fix my BIOS chip after a bad upgrade?

There are a few ways to acquire a replacement BIOS chip. Online resources include the following:
The FlashBIOS Site
Leander Computing

These places deal in replacement BIOS chips for nearly all motherboards out there that contain an Award or AMI BIOS. There are many more out there, but these are ones I personally have heard about and have had people tell me they are reliable. As for prices, you will have to contact them directly. It's my understanding that each BIOS upgrade varies in price. I believe that the chip type and motherboard type will determine the price. You can also buy your own BIOS chip and program it yourself. However, a EEPROM programmer is required for this. In the end, consider the cost of purchasing a new chip for your motherboard versus the cost of purchasing a new motherboard. You may be better off with a new motherboard over a new BIOS as the new motherboard may offer newer features and offer a greater amount of upgrades as well.

How can I save my BIOS settings so that I can restore them later?

There are a few methods that one can save the current settings. You can use the flashing utility to save the current BIOS into a file or you can use printscreen to print each of the BIOS setup screens. With this method, a parallel printer is required and must be attached to the systems parallel port. A network printer will not work, nor will a USB printer. Within each of the BIOS setup screens, you can press the print screen key on the keyboard (this is actually a BIOS service your calling) and the output of the current screen will be sent to the printer port.

What's a flash utility and where do I get one?

hardtellin from Hardware Central asks:

A flash utility is a small program that is specifically designed to replace the computers BIOS programs contained within the motherboards BIOS ROM. These flashing utility programs are also designed to backup the current BIOS information into a file as well as provide information on the current BIOS version. Newer versions of these programs are developed to support newer flash ROM chips that come out onto the market. In some cases however, these newer flashing programs drop support for older flashable ROM chips. Usually those chips that can be found on the late model 486's when the flashable ROM chips first started to appear and the earlier Pentium motherboards.

In most cases, these flashing programs can be downloaded via the Internet directly from your motherboard manufacturer's website or from your computer manufacturer. In the case of retail systems such as Hewlett Packard, Dell, and Compaq, a system specific program may be required. This is especially the case of Compaq systems. With nearly all Compaq systems, the BIOS is split into two parts. Half of the BIOS is located on the motherboard and the other half is located on the hard drive. For this reason, consult your user manual or online documentation for complete details about your system.

Why can't I access my BIOS? I press DEL but nothing happens!

This is most likely because the particular sequence to enter your systems BIOS is not by pressing the Del key. There are several key combinations that work and each system uses their own. When you first power up your computer, view the POST (Power On Self Test) messages. Typically the message prompting you to enter the BIOS setup will be displayed soon after the memory check is completed. Within this message the proper key sequence will be displayed. If you own an HP, Dell, Gateway or other manufacturer, a "splash" screen may be present that hides the POST messages. You can bypass this by pressing the Esc or Tab keys to view the POST messages.

Acer: - Ctrl+Alt+Esc

ALR PC: (F2) or (Ctrl)(Alt)Esc)

AMI BIOS: (Del), (F1) or (F2)

AST, Advantage, Award, Tandon: - Ctrl + Alt + Esc

Award BIOS: (Del) or (Ctrl)(Alt)(Esc)

Compaq: (F10) (do this when the cursor is in the upper right corner of the screen blinking)

Dell: - F1 or Del.

Dell: - Some require pressing reset twice

Dell: - Ctrl + Alt + Enter


Gateway 2000: - F1

Hewlett Packard: - F1


    Older Models - In order to get into the configuration of the IBM setup screen (CMOS) screen you need to hold down both mouse buttons during bootup.

    Aptiva - Press F1

IBM PS/2: (Ctrl)(Alt)(Ins) after (Ctrl)(Alt)(Del)

IBM PS/2 with reference partition: - Press Ins during boot

Some PS/2s, such as 75 and 90: - Ctrl Alt ?

Some PS/2s when pointer at top right of screen: - Ctrl + Ins

Leading Edge:

    Fortiva 5000 - <Ctrl> <Alt> <A> or <Ctrl> <Alt> <S>

NEC: - F2

Packard Bell: - F1 or F2

Phoenix BIOS: (F1), (F2), or (Ctrl)(Alt)(Esc)

Phoenix BIOS: - Ctrl Alt S

Phoenix BIOS: - Ctrl S

Phoenix BIOS: - Ctrl Alt Ins

Sharp Laptop 9020: - F2

Sony: (F3) while you are starting the PC, then (F2) or (F1)

Tandon computers: - Hold down the <Esc> key after turning on power

Tandon: - Ctrl + Shift + Esc

Toshiba Laptops: - Toshiba Utility

Toshiba: - Press Esc during boot

Toshiba, Phoenix, late model PS/1 Value Point and 330s: - Press F1 during boot

Olivetti PC Pro: - Shift Ctrl Alt + Num Pad Del

Miscellaneous PC's: - Ctrl + Esc or Ctrl and Alt and +

Zenith: - Ctrl Alt Ins

NOTE: Some new motherboard designs have a jumper on the motherboard that disables access to the BIOS. In order to access the BIOS setup, this jumper will have to be disabled. You cannot access the BIOS setup until this jumper has been disabled.

How do I tell what version of the BIOS is currently installed on the motherboard?

For Tyan motherboards: TYN [motherboard model] Vx.xx MM/DD/YY

For QDI motherboards: P6I440BX BrillianX-1S/2K BIOS V1.2SLRC Jan.07,2000


What does CAS Latency 2 and CAS Latency 3 mean?

CAS Latency, What Is It?

Over the last three years or so, memory manufacturers have been releasing new and faster memory modules at an ever quicken pace. Some are updates of existing types, while others are redesigns and still others are entirely new innovations. We've moved quickly from FPM to EDO memory, and then on to SDRAM. Then SDRAM jumped from its initial release at 66MHz to 100MHz and then to 133MHz. In the last year we've seen Rambus DR DRAM, and most recently DDR DRAM memory. Now, after having digested all of these changes and innovations, and all the hype about "substantial speed increases", the memory manufacturers, distributors and retailers have decided to bombard us with the technical terms as to why their product is better then that of another company. One such example has been the issue of CAS Latency. Recently, a whole raft of resellers have been publishing comments that the CAS Latency on their Brand X modules are a huge improvement over that of Brand Y modules sold elsewhere. Unfortunately, none of them go quite far enough to explain just what this means. Is CAS Latency an issue? Is it hype, or is it something I should be careful about? What does it mean?

Maybe yes, and maybe no. We know you don't like that answer, but the truth is that much of how CAS Latency effects your computer depends upon the component make-up of your computer, how you use it and the programs you use.

Although our review of Memory Speeds digs into these issues, let's take a quick look at the issue of memory timing by itself. CAS Latency (CL) is the ratio between column access time (tCAC) and the clock cycle time (tCLK), rounded to the next higher whole number. The formula is rather simple really, divide the column access time by the clock cycle time, then raise the result to the next whole number.

As an example, if the tCAC is 20 nanoseconds and the tCLK is 10 nanoseconds (a 100 Mhz system bus), then the CL would be 2. If tCAC is 25 nanoseconds, then CL would be 3 since 25/10 = 2.5 (rounded up to 3).

Okay, so what does all of this mean? To understand that, we need to understand the meaning of a few other memory timing terms. By the way, for clarity purposes, we will be referring to a 100MHz system bus.

  • RAS - Row Access Strobe
  • CAS - Column Access Strobe
  • tRCD - The length of time between RAS and CAS access.
  • tRP - The length of time to switch between memory banks.
  • tAC - The length of time to prepare for output.
  • tCAC - The column access time

RAS and CAS normally appear in technical manuals with an over-line as in RAS or CAS.

In lay terms, data is transferred from memory to the CPU as follows:

  1. The CPU sends a signal specifying the memory row and bank that it wants to access via the RAS line.
  2. After a specific period of time (tRCD) the CPU sends a signal on the CAS line, specifying the column it wants to access.
  3. After tCAC (column access time) the data moves to the output line, from where it is transferred with the next clock tick.
  4. The CPU expects the data to appear upon a specific clock tick after sending the request.

Since the clock cycle is the inverse of the bus speed, it is defined for our purposes here as 10 nanoseconds. On a 100 Mhz. bus, data transfer takes about 2 nanoseconds. According to the PC 100 specification, tAC is 6 nanoseconds, and it takes about 2 nanoseconds for the signal to stabilize.

6 nanoseconds (tAC) + 2 nanoseconds to stabilize = 8 nanoseconds
8 nanoseconds + 2 nanoseconds for transfer time = 10 nanoseconds = 1 clock tick

Therefore, in burst mode, the three data transfers after the first one that requires 50 nanoseconds, data can be transferred in one clock cycle. SDRAM is a multi-bank architecture, and during the occurrence of data processing, the chipset can leave a given row of a given bank (which has been accessed before) "open". As an example, if the very next request accesses the same row, the chipset does not have to wait until the sense amps are charged. This is referred to as a "page hit". The RAS to CAS latency will be 0 (zero) cycles and the output buffers will contain the right data after the CAS latency. In simpler terms, a page hit makes sure we only have to wait until the right columns are found on the sense amps, which already contain the requested row.

There is a down side though, as the row requested by the chipset might not be the one that is open, which is referred to as a page miss. In that case the RAS to CAS latency can be 2 or 3 clock cycles, depending on the quality of the SDRAM. If the chipset has left open a certain row on a certain bank, and the data requested is in a different row in the same bank, latency gets worse. When this occurs, the sense amps have to write back the old row before they can charge the new one. Writing back the old row takes a predetermined amount of time referred to as tRP (Precharge Time).

SDRAM modules are usually defined by three numbers, such as 2-2-2 or 3-2-2. The first number refers to CAS Latency, the second to tRP (time to switch between memory banks), and the third to tRCD. Bear in mind that these numbers mean different things for different bus speeds. As an example, these are the calculations for 100 Mhz. (1 clock cycle = 10 nanoseconds):

At 100 MHz.

tCAC  = 25 nanoseconds 25 / 10 = 2.5 - rounded to 3 or 3-2-2
tRP    = 20 nanoseconds 20 / 10 = 2
tRCD  = 20 nanoseconds 20 / 10 = 2

If we were to calculate these figures at 133 Mhz., with 1 clock cycle equal to 7.5 nanoseconds, the results would be:

At 133 MHz.

tCAC  = 25 nanoseconds 25 / 7.5 = 3.33 - rounded to 4 4-3-3
tRP    = 20 nanoseconds 20 / 7.5 = 2.67 - rounded to 3
tRCD  = 20 nanoseconds 20 / 7.5 = 2.67 - rounded to 3

This second example, with a CAS Latency of "4", would be invalid in a 133 Mhz. system, as the PC 133 SDRAM specification does not permit this.

The Bottom Line

CAS Latencies are usually written as CAS2 or CAS3, so just how important is this?

In the real world, unless your system is up on the cutting edge of technology and you're pushing performance to the limit as do some over-clockers, or gamers, it may have some relevance. On the other hand, in everyday systems the relevance is nominal at best. CAS3 means that at 100 Mhz., the amount of time required for the first memory access in a burst is increased by 10 nanoseconds or less. Divide this figure by 4 to average the increased time across four bursts, and you have an improvement of less than 2.5 nanoseconds over CAS2. We need to underscore the term relevance as it pertains to CAS Latency and changing memory modules on the average system. If you had a Pentium III 600 to 866MHz. computer, as an example, and you used this for surfing the Internet, using Microsoft Office or Corel Office, Adobe products etc., and changed your memory modules from those having CAS3 to CAS2 latencies, you wouldn't be able to notice any difference. But again, if you are pushing your system to the limits, this could become critical.

How can I disable ACPI and what are the advantages and disadvantages of enabling ACPI?

First off, I think a little introduction is needed as to what ACPI is.

ACPI (Advanced Configuration and Power Interface) is a power management specification that allows the operating system to control the amount of power distributed to the computer's devices. Devices not in use can be turned off, reducing unnecessary power expenditure. ACPI defines a new interface to the system board, and enables the OnNow design initiative for instantly available PCs.

ACPI is actually a substitute for APM (Advanced Power Management) at the hardware-software level. Unlike APM, which deals with the power management directly through the BIOS, ACPI, instead exposes the tables present in the various installed hardware devices in the system to the operating system. ACPI, in effect, hands off control of power management to the operating system. ACPI is merely a standard implemented by hardware vendors to provide standardized interfaces that are ACPI compliant. In this manor, much of the work done for power management is thus performed by the operating system instead of the BIOS. ACPI was developed by Intel, Toshiba, Phoenix, Compaq and Microsoft to establish common interfaces for the hardware devices in a system to allow various operating systems direct control over the power management of the entire system, devices and operating system alike.

Some advantages are:

1) Moving power management functionality into the OS makes it available on every machine on which the OS is installed. The level of functionality varies from machine to machine, but users and applications will see the same power interface on all ACPI compliant machines.

2) Power management is not restricted to the BIOS and hardware levels. With ACPI and a suitable model, applications can tune themselves and conserve power.

3) There is much less state information for the BIOS to retain and manage because the OS manages it. This leads to a simpler implementation at the BIOS level.

4) Power management algorithms are unified in the OS, yielding much better integration between the OS and the hardware.

5) The OS can deal with power management of devices dynamically, as the interface provides dynamic registering or loading and unloading of devices.

Some disadvantages are:

1) Problems will arise when an ACPI BIOS puts an _ADR device into a deeper sleep state than its bus is expecting. It is important to remember that any buses (including PCI) do not expect devices to disappear from the bus when they are powered down. If a subsequent enumeration of that bus takes place, the bus driver will believe that the powered-down devices have been removed from the system. In Windows 2000, this may result in an "Unsafe Surprise Removal" dialog box. For Windows 98, no dialog box will appear; the disappearance of an IDE device will result in an IDE error bluescreen.


How do I clear the password?

PC Protect passwords Text passwords BIOS passwords

YODA74 from PCGuide:

If going with Password Protected PC,turn off the system and search the motherboard for a Clear CMOS Password jumper. This jumper lets you clear the password without wiping out the entire contents of CMOS RAM. The jumper can be hard to find. Check the motherboard's documentation or manufacturer's Web site for information. Once you find the proper jumper, set it and reboot the system. When you see a BIOS message that says, "Password cleared," turn off the PC, reset the jumper, and boot normally.

If there's no jumper, remove the battery, which wipes the CMOS RAM's contents. Some chips hold a latent charge longer than others, so it may be a while before you can return the battery to the PC. (If you put the battery back in too quickly, the CMOS's memory may not have cleared yet.) After you reset the date, time, and hard-drive parameters, use the BIOS Default option to restore general settings.

Is my BIOS flashable?

To determine if your motherboard uses a CMOS chip that is flashable your going to have to examine the chip ID on the chip itself. In a lot of instances there is a sticker on the top of the chip that identifies the manufacturer. You can pull the sticker back gently to reveal the chip information. Replace the sticker once you have acquired the chip information. The following list contains chips that are flashable:

m29F010: AMD 5 volt flash ROM
Am28F010, Am28F010A: AMD 12 volt flash ROM
AT28C010, AT28MC010, AT29C010, AT29LC010, AT29MC010, AT49F002T: Atmel 5 volt flash ROM
CAT28F010V5, CAT28F010V5I: Catalyst 5 volt flash ROM
CAT28F010, CAT28F010I: Catalyst 12 volt flash ROM
28F010: Fujitsu 12 volt flash ROM or ISSI 12 volt flash ROM
HN58C1000: Hitachi 5 volt flash ROM
HN28F101, HN29C010, HN29C010B, HN58C1001, HN58V1001: Hitachi 12 volt flash ROM
A28F010, 28F001BX-B, 28F001BX-T, 28F010: Intel 12 volt flash ROM
M5M28F101FP, M5M28F101P, M5M28F101RV, M5M28F101VP: Mitsubishi 12 volt flash ROM
MX28F1000: MXIC 12 volt flash ROM
MSM28F101: OKI 12 volt flash ROM
KM29C010: Samsung 5 volt flash ROM
DQ28C010, DYM28C010, DQM28C010A: SEEQ 5 volt flash ROM
DQ47F010, DQ48F010: SEEQ 12 volt flash ROM
M28F010, M28F1001: SGS-Thomson 12 volt flash ROM
28EE011, 29EE010: SST 5 volt flash ROM
PH29EE010: SST ROM Chip - Flashable
TMS29F010: Texas-Instr. 5 volt flash ROM
TMS28F010: Texas-Instr. 12 volt flash ROM
W29EE011, W29C020C, W49F002U: Winbond 5 volt flash ROM
W27F010: Winbond 12 volt flash ROM
X28C010, X28C010I, XM28C010, XM28C010I: XICOR 5 volt flash ROM
29LVxxx - 3V Flash memory (rare)
28Cxxx - EEPROM, similar to Flash memory
27Cxxx - With window. EPROM: read-only, requires programmer to write and UV to erase

Anything without a window that doesn't have a 28, 29, or 49( the latest chip models) as the preceding numbers of the part number is most likely a standard ROM and not flashable.

edwelly from TechIMO asks:

What does BIOS stand for?

BIOS stands for Basic Input/Output System. For a detailed explanation of the BIOS and how it works, please refer to the beginning of this FAQ for more information: What is the BIOS and how does it work?

What does CMOS stand for?

CMOS stands for Complementary Metal Oxide Semiconductor. Information saved in the BIOS setup program is stored here in RAM. The settings are maintained through the CMOS battery located on the motherboard. Power is trickled to the CMOS IC to ensure the settings are not lost when the system is powered down or unplugged. Battery life varies with each type used. In most cases, you can expect about 3-5 years life span out of most CMOS batteries. In some cases, however, batteries bought from stores are DOA. Always check the expiration date on batteries before purchasing them. Here's a classic case of buyer beware. Once you buy it, it's yours to keep.

For a detailed examination of what CMOS is, please refer to the following website for information: Introduction: Complementary Metal Oxide Semiconductor (CMOS) Structure.

Shadowfax from XiBase asks:

What is hot swapping the BIOS? [don't no the proper name for replacing the BIOS when the computer is already running]

Tmod writes:

Hot swapping is a means of recovering your bios in the event of a power failure or a corrupt flash file. The Hot Swapping process involves finding or gaining access to a computer that has the same type of BIOS ROM chip you have now. Not necessarily the same manufacturer but the same page bytes as well as programming voltages and pin out's.

The process would involve booting the computer that you are going to use to recover your bad bios and after the boot is complete swap bios chips while the power is still applied and then flash the bios with the flash file that is for your broken computer. This procedure is not without risk as you may ruin the motherboard in the computer you are trying to use to recover the bad flash bios. Static electricity is the common enemy when it comes to any electronic component.

When performing a flash in this operation the use of the /F parameter is required. Using this switch will force the flash to go through(Award Bios Only). Also, this parameter must be used by itself. No other parameters can be used in conjunction with it.

Care should be taken if you are considering performing a how swap. SO NOT USE A METAL TOOL TO EXTRACT THE CMOS CHIP! Use a small strong piece of plastic or other nonconductive device to perform the extraction. Care should be taken when you insert the dead BIOS also. Attention should be given to the leads. These are fragile and conductive. Hold the chip from the ends and not the sides. You could easily pile on more damage tot he chip from ESD if you do. Carefully insert the chip. DO NOT FORCE IT! You will most likely bend one of the leads in doing this. Slowly maneuver the chip into place. A little force it fine, just be careful to not push to hard.

korgul from TechIMO asks:

How do I replace the CMOS battery?

Replacing the battery on your motherboard is a straight forward task. With any new motherboard out there and nearly all motherboards since the Pentium was introduced, the CR-2032 battery has been used to provide power to the CMOS.

This battery is pretty much the standard with all motherboards now. To replace the battery, examine the retaining mechanism for it. It seems that just about every motherboard uses a different method of retaining it. Once you have figured out how to remove it, just pop it out and insert the new battery.

With some older motherboards, the battery was soldered on. This is especially true with the 386 and early 486 motherboards. The biggest problem with these batteries was corrosion. A leaky battery would eat the copper on the motherboard and other components around it. To solve this problem the industry has moved to the battery implementation using the CR-2032. However, there is still the issue of how to replace the older batteries. If your adept at soldering, desoldering the battery and replacing it should be a straight forward procedure. For those of us who would rather not solder, there is a way around it. With a lot of the older motherboards, a jumper was available to attach a battery. This allowed for easy replacement of the battery on these older motherboards. If this is the case, you can simply purchase a battery from a local computer store or one of the big name brand stores like CompUSA, etc.. Something like the following:

The lead for it connects to the jumper on the motherboard for an external battery. Ensure that you check your motherboard for the type of battery and the method of replacement, especially for the older motherboards. Using the incorrect battery may lead to a corrupt BIOS and/or dmage to the physical CMOS IC.

Fury from XiBase asks:

What do I do if my power went out in the middle of a BIOS flash and my computer will no longer start?

Tmod writes:

Most BIOS's as of today have a boot block feature for situations such as this. This feature will allow the computer to boot to the floppy and flash the BIOS with a new flash file that will over write the data corruption as a result of the power failure. At certain times the video will not be available and you will have to create a flash disk that uses a autoexec.bat file that will automatically flash the BIOS without user intervention upon boot up. If you still don't have any luck with that you could always try the Hot Swap procedure or get a replacement BIOS from several different vendors.

Matthew Kieren from Binary’s BIOS Mods asks:

What are the optimal settings for my BIOS?

That's a question that only you can decide on actually. Every system is used for a different purpose, graphics workstations, home based server, development workstation, all of the above, or just e-mail/Internet system. Each feature has it's own purpose and each has it's advantages and disadvantages. For the best reference, I could copy the entire document from Adrian Wong's site, but then I would be wasting bandwidth. See for yourself. The Definitive BIOS Optimization Guide, an absolute must for any BIOS tweaker/hacker. Also, be sure to check out the bottom of the page. There you download the entire document in various formats.

Where can I find information on how to modify the boot logo?

Tmod writes:

You could always post a message here at Bios Central Forums in the Advanced BIOS Mods area pertaining to what logo you want and the possibility of doing the mod. You will need a a utility that is meant for the BIOS type and version that you are working with. For example you would use Cbrom for the Award BIOS's and AMIbcp75 for the AMI BIOS's. There also is a utility named Awdhack that will do the Medallion BIOS's and some of the ones that Cbrom won't do. There are a few little requirements that need to be met before this can all take place. If you are changing the EPA logo there are different versions of the logos. If you are going to do a full screen then yet again there are different needs to be met. This modification is not hard and if anyone has a desire to change the picture they see when their computer boots up then this is for you.

"THIS IS FOR AWARD BIOS'S ONLY" You will need three files to change the boot or epa logo and flash it. (1) Cbrom "Either version 2.07 or 2.15 (2)Awdflash "The newer the better" (3) The logo

1) If you want to use your existing bios you will have to make a copy of it for the modification. Using a boot disk with Awdflash on it just type Awdflash /SY and that will make a backup copy of it. Just name the backup file backup.bin. If you want to use a newer bios flash file there is no reason to do this step.

2) If you are going to change the logo(s) in a newer bios flash file just download the version that you want and extract it to a folder in your system. Also copy cbrom to this folder as well as the logo (s) that you will be changing to. If you are going to use a backup of the bios flash just copy it from the floppy to the same folder where cbrom and the logo(s) are located.

3) Help for Awdflash and Cbrom is the following commands Awdflash /? or Cbrom??? /?

4) Open the DOS prompt window In Win9x and navigate to the folder where the files are located.(Windows NT, 2000, XP have issues with DOS programs and it is best not to run them within the OS. If you have one of these OS systems download the BiosMod Utility V1 in the utility download section.)

5) Make sure that all files needed are in the same folder.

6) We assume you already have a favorite .BMP or .EPA of a penguin or daemon handy. (640x464, 16 colors, Windows BMP or the proper EPA version)

7) For kicks, examine your old BIOS ROM: CBROM??? mybios.bin /D See the various components there? The one we're after is the logo bitmap, by default "welcome.bmp" or epa.

8)Modify your bios file: CBROM??? mybios.bin /logo penguin.bmp for the full screen boot logo or CBROM??? mybios.bin /epa myepa.epa for the epa logo. This overwrites mybios.bin, creating the file for your new BIOS. If your logo is too complicated and doesn't compress well, you may run out of space. You can use CBROM to tell you whether or not your BIOS image with the new logo is "full" or not.

9) If all went well and you saw the program add the logo(s) It will show a percent value you have succesfully added a new logo or epa. Now copy the modified bios file to the floppy.

10) Now is the time to reflash the chip and see if you did it correctly. Boot the computer using a boot disk with no config.sys or autoexec.bat and the Awdflash program on the disk as well as the modified bios file. Just type in Awdflash and the flashing process will begin. Answer yes when it asks if you want to make a backup of the current bios.


Troubleshooting a BIOS upgrade

The PC does not boot after upgrading the BIOS:

If you have removed the CMOS chip for flashing, double check that you have inserted the CMOS properly. Ensure that the orientation of the IC is proper and that all pins are properly inserted. If you have flashed the BIOS with the wrong BIOS update, then the only recourse is to replace the CMOS IC outright.

You accidentally reset or power down the system during the BIOS flash. Now the system won't boot:

Basically what has happened here is the BIOS was only partially programmed. In this case, the BIOS is corrupt. If possible, you can remove the IC and reprogram it in a EEPROM programmer. Another option is performing a "hot swap" of the chip with another motherboard with the same chip. Otherwise, a replacement of the CMOS IC is required. There is no chance in fixing the IC in it's current state.

The BIOS upgrade proceeded properly, but now the system performs sluggishly, erratic or error appear that never occurred before:

Several things can attribute to this. It could be caused by a bad flash. In this case, reflash the BIOS with the backup of the BIOS made during the flash (you did make that backup...right?). After restoring the backup, you can reflash the BIOS again with the new update. Other possibilities include new settings within the BIOS. Memory timings area big issue. Enter the BIOS setup program and restore BIOS defaults or Fail Safe Defaults. Then, once your system is stable, tweak the memory timings to you desire. Other issues can be incorrect port settings, features that were enabled when the flash took effect and features that were disabled. Check the following: "System Bootup Speed", "Speculative Lead Off", "Turn Around Insertion", "ISA Speed - ISA Clock to:", "16 Bit Recovery Time", "Pipeline Cache Timing", and other speed settings that may effect performance.

You just upgraded the BIOS and now cannot boot from the floppy drive:

Enter the BIOS setup program and check the Boot Sequence. Ensure that the sequence is set to A:/C:. Ensure that the floppy drive is setup properly in the BIOS as well and that the system is not looking for a B: drive too.

You get a message saying: "Incompatible BIOS translation detected - unable to load disk overlay":

A lot of people upgrade their BIOS to get support for larger hard drives. In some cases, users have installed a software overlay that allows the operating system to properly see the entire hard drive. What happens with the BIOS in this case is the LBA (Logical Block Address) is now enabled. What you will need to do is enter the BIOS setup program and disable LBA mode for the hard drive in question. If more than one drive is configured for a software disk overlay, then you'll need to configure all drives properly by disabling LBA on them. With some disk utilities, the user can remove the software overlay safety. Beware. This is no guarantee that the system and the hard drive will work properly. Always backup your data before removing a disk overlay. You may not be able to get it back.

Your system boots with an error message saying "BIOS Boot Block Loaded":

What most likely has happened here is the BIOS is not being read correctly by the system. This is usually due to a BIOS not being cleared properly. Power down and clear the BIOS. Ensure that you pull the system power cord when clearing the BIOS to ensure proper erasure. Resetting the BIOS, in most cases, will clear this up. If the problem persists, then insert a bootable floppy and reflash the BIOS with the backup you created during the flashing. Once your BIOS has been restored, you can proceed with flashing the BIOS again. After flashing the BIOS, always clear it before proceeding.

You may also receive this message if the BIOS flash did not complete, you flashed the BIOS with an incompatible BIOS update, or some other anomaly occurred. In any case, you should be able to recover the BIOS as long as you can boot to a floppy. Remember to boot from a floppy that doesn't have any drivers being loaded. Once you have booted the system you should be able to either restore the BIOS from the backup you created or reflash the BIOS with the BIOS update.

You get an "Insufficient memory" error when running the flashing program:

This means that the flashing utility has run out of memory to perform the flash. Enter the BIOS and disable the video and system caching as well as all types of Shadow Memory. Make sure the boot floppy you are using is not loading ANY device drivers, such as CD-ROM or mouse drivers.




P. McNichols, BIOS Update Guidelines, 1990 Dynamic Learning Systems.

S. Bigelow, Troubleshooting, Maintaining & Repairing PCs 2nd Ed., 1996 McGraw-Hill.

A. Wong, The BIOS Optimization Guide Rev. 6.2, 1998-2001.


Copyright © 1988 -  by Bob Hurt. All rights reserved. Bios Central is a trademark of Bob Hurt.

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