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During the initial phase of booting up, during the first 2 to 6 seconds, you are given a chance to enter the BIOS setup for the BIOS ROM chip on the motherboard. Many settings for your computer are configurable in the BIOS setup application.

It is pretty cryptic and I do not recommend changing any settings in the BIOS if you are a beginner. The manual that came with the motherboard will give limited instructions for the correct settings.

If you don't have a manual for your motherboard, you can usually download one from the motherboard manufacturer's website.

If you don't know who made your motherboard, you could do several things to help you find out who did:

1. Open up the case and read the name and model number printed on the large motherboard

2. Download, extract and install SiSoftware Sandra. Run the program to detect your computer's hardware details

3. For Award and AMI BIOS, write down the string of numbers that appear at the bottom left hand side of your first screen during the initial bootup. You can hit the pause button on your keyboard to freeze the boot process to give you time to write down the numbers. Hit enter to continue booting up. Now go to Wim's BIOS page. Click the Award Numbers or AMI Numbers link at the top left of the page. You can match the number you wrote down with your motherboard manufacturer and model number.

You can enter the BIOS setup usually with one of the following keys or key combos:

DELETE
F1
F2
F10
CTRL+ALT+ESC
CTRL+ALT+ENTER
CTRL+ALT+S
CTRL+ALT+INSERT
CTRL+A
CTRL+F1
CTRL+S

Usually when you are first booting up, the first screen will display in text which key(s) to press to enter setup.

On some machines, you have to hit ESC first to clear the manufacturer's logo.

For an AMI BIOS it's usually DELETE
For an Award or Phoenix BIOS it's usually CTRL+ALT+ESC, F2 or DELETE
For a Compaq BIOS it's usually F10

From Bob:

From the point at which you hit the power switch, the computer starts workin--beginning with a self test (POST) that uses information about the computer stored in special memory (CMOS.)  CMOS (Complementary Metal-Oxide Semiconductor) is a special kind of RAM (random access memory) chip that has really low power requirements, and the data stored there is supported by very small rechargeable NiCad (nickel cadmium) batteries.

The data stored in CMOS ("sea-mawss") are variables used by the BIOS (Basic Input/Output System) routines stored in ROM (read-only memory), albeit ROM used for the storage of a BIOS image is typically only found in early PC's.  Most BIOS programs and routines are now found in EPROMs -- EPROMs can be updated with software to add changes and patches to BIOS programs.  They, typically, have a limited capability to be written to a number of times.  In recent years, it seems that manufacturers have had great opportunity to exercise this capability.  The disadvantage to using EPROMs for this purpose is that virus software can be written to alter or destroy BIOS code stored in EPROMs.  When the computer starts, programs are automatically loaded from BIOS ROMs and are executed.

The purpose of BIOS routines is to test the computer to see that basic functions are present with the POST (Power-On Self Test), provide a Setup program to access and change the data stored in CMOS, to load an operating system, and to provide basic communications among computer components.

Those three paragraphs introduced a few key concepts regarding the BIOS.   Recapping, The BIOS (Basic Input/Output System) is a program and set of functions that resides in ROM (Read-Only Memory.)  BIOS routines:

• run the POST (Power-On Self Test)
• load a rudimentary operating system
• permit configuration information to be stored in CMOS (Complementary Metal-Oxide Semiconductor memory)
• use configuration parameters stored in CMOS
• load an operating system
• provide communications functions that allow an operating system to control, read from, and write to the hardware

When the computer is turned on, the very first thing the machine does is read from the BIOS ROM and run the BIOS programs.  Among the earliest will be one that will run the POST, and the POST checks for your keyboard, storage devices, and other hardware peripherals before finding, loading, and running the operating system. The information about how the hardware is configured is given to the POST from data stored in CMOS memory.

Normally, all data from memory areas supported by your system are lost when the power is turned off.  Most of the data that will be reloaded into memory are stored on disk. Before the system knows how to read the disk, however, it needs to load data into working memory that will let it recognize and use the hardware in the system including the hard drive where essential system data is stored. This essential data, on how to read the disk and how to work with other hardware, comes from BIOS ROMs and CMOS. CMOS is a 64-byte region of memory, supported by battery power, used to store the variable system hardware configuration information.

If the battery supporting CMOS memory dies, the configuration information is lost, and your PC may or may not boot. Whether it boots, or not, depends on whether there is a store of default information sufficient to get up and running. Fairly often this is not the case.  In general, you will have no access to the full computing power of the system until you restore the configuration information to CMOS RAM.  This requires restoration of power to CMOS.

Against this unfortunate day, when your CMOS loses power, you should enter the system setup program and write down the CMOS settings you will need to set to get your system running again. Then you'll be ready when the data in CMOS gets lost. Even the system setup program is loaded from ROM/EPROM by BIOS routines.

Now, we need to alter the information above, just a little.  The original IBM PC-AT had only 40 bytes of storage available for CMOS parameters.  This was quickly expanded to 64 bytes.  With the advent of EISA and PS/2 systems, 64 bytes was no longer sufficient, but problems with the original design prevented adding memory for CMOS directly.  An additional "black block" was added to increase the available CMOS memory to over 1KB, and this was accessed using a different addressing schema. As motherboard design developed, BIOS code was again found on a single chip.  It is not atypical to find a 1 to 2 MB BIOS chip on motherboards today.

The data in CMOS is used by the POST and the BIOS routines (Basic Input/Output System) to configure the system. Some devices, such as SCSI driver controllers, contain their own BIOS information and perhaps even their own CMOS data, but most of the hardware devices in the computer depend on CMOS RAM on the motherboard.

When the system first starts up, you can interrupt the POST to get into the setup program. The setup program accepts human interface input to store information (parameters) for the system in CMOS.  These parameters will be used by the BIOS programs to configure the system.  How you invoke and use the setup program vdo this varies from machine to machine and is nicely covered by NtwrkLarry in his message above. This keystroke sequence or combination is usually displayed on the monitor when the system is first turned on. This screen message typically reads "Setup - keystrokes" or "keystrokes to enter Setup..." In general, you must be quick to enter the keystrokes during or immediately after the memory check or your opportunity to start the setup program will pass.

The Setup program allows you to examine and alter the data stored in CMOS. If your entry of keystrokes is successful, you should see a message stating "Entering Setup..." followed by the first setup menu. Typically, the first setup menu is either a menu of menus or the Standard CMOS Setup parameters menu. There should be an instruction bar or box at the bottom of the screen that gives the keystrokes required to navigate the setup program.

Note of Historical Interest: Once upon a time (80286), CMOS setup programs came on a bootable floppy disk.

Where there's a Standard CMOS Setup parameters screen, there is generally also an Advanced CMOS Setup parameters screen just a few keystrokes away. There may be other menus as well. Most of your parameter changes, if necessary, will occur using selections from the Standard and Advanced menus. Here is where you will find disk, video, communications port, boot sequence, data and time, chipset, power, PCI and other parameters with settings that are specific for your system and its hardware. Remember these menus may vary from system to system. Some menus are organized by functional groupings such as peripherals, power management, and so forth.

Standard CMOS Setup: Date and Time, Hard Drive Parameters, Floppy Drive Parameters, Video Type, Keyboard

Advanced CMOS Setup: Used to select special features or fine tune how resources are used by your system. System Boot-up sequence, Cache memory enable/disable; ROM/RAM shadow options, and others.

Power Management: I generally just turn this off. I've yet to see the computer/BIOS/operating system that handles power management effectively and some of them do it quite poorly. I hope they keep trying until they get it right. You'll see what it's about when you get there. Ok, Ok, I leave it on until it screws up and then I turn it off.

PCI Control: There shouldn't be a reason to play in this area. PCI should be plug and play.

Passwords: You get to setup a password that will be used during the POST. The options are usually "disabled", "setup", and "always." Unless you have a security problem, setting a password for entry to the CMOS setup is probably NOT a good idea. "Setup" only protects the BIOS settings. "Always" prevents the system from starting at all without the password. I never set this, but then my environment is pretty secure. The good news is that this can prevent the machine from getting past the POST on startup. The bad news is that, if you forget your password, you probably need to open the case. This only keeps the honest people honest. The thieves will know that you can open the case and remove (or short out, if your MB allows) the CMOS battery to reset the CMOS to defaults. If you ever need to steal into your own machine, you better know what the CMOS parameters were because if you lose the password this way, you lose all of the other CMOS data as well. The motherboard manual should have the best method for getting past a forgotten password. Sometimes, people will enter a password to your machine to keep you from getting in. They think this is funny; you don't.

Getting in: There are some default passwords and some common passwords that you can try: AMI, Award, AWARD_SW, bios, BIOS, biostar, setup, SETUP, cmos, CMOS, system, computer, AMI_SW, AMI!SW/, AMI?SW/, DOS (really), password, asdf, and qwerty. Try the initials of the BIOS manufacturer. If those passwords didn't work for you, get out your motherboard manual and start reading. You are looking for the jumper that will reset the CMOS. If the manual doesn't help, find your CMOS battery on your motherboard. Then look for a jumper with three pins close by. The jumper should be covering 2 of the 3 pins. Change it to the other two and power up the system for a few seconds. Then turn the system off and replace the jumper to its original position. If you can't find a jumper, remove the CMOS battery for a few minutes. If that didn't work, remove it again and wait longer--goto lunch. If the CMOS battery is soldered down (you have an old motherboard and should consider a new one), consult with the vendor or manufacturer of the board. If you can't do that, get drastic, discharge the battery with a resistor, say 40 ohms or so. Crank it back up, and you're hoping the password is now a thing of the past. If the system is still asking for a password, try that list of passwords again. Some of them are default passwords for the BIOS manufacturers.

A caveat: you can shoot yourself in the foot changing CMOS parameters and render the machine unable to boot. Know what the parameters should be and don't change those things about which you have no knowledge or no instructions. It is probably safest to change one thing at a time and write down the value of the parameters before and after you make a change. If something didn't work and now it works, leave it alone. If you changed a parameter and don't notice any difference, you may have miscalculated cause and effect considering how your combination of hardware and OS work together. If you are expecting maybe subtle changes, run a benchmark program to determine just what you gained or lost by making a change. After each change, reboot the system and make sure the system is performing as expected. If you entered CMOS Setup and are not sure that you made changes or not, and it was your desire to make no changes, make sure that you exit the setup program without saving any changes. If you made changes and are ready to exit the the CMOS Setup program, make sure you exit and save changes. Your system will re-boot when you exit Setup.

Standard CMOS Setup Menu

At the Standard CMOS Setup menu, you will be able to configure the time, date, hard drives, CD-ROM drives, floppy drives, the primary display type and the keyboard. Most of the time, these are the critical settings that may require your intervention. If most of these are not correctly configured, there's a good chance you may have trouble booting the system.

While the commonly found CMOS parameters are explained here, the book that came with your motherboard and/or BIOS will be most useful for explaining parameters that might be unique to your motherboard/BIOS.

The Date and Time parameters are mostly for convenience. They can be set in CMOS, but it is common for most Operating Systems to have an associated Date and Time utility that will set the clock from the running system.

The video display information to be set is rudimentary. Typically, you get to choose between basic VGA mode and one of several older modes such as MDA, CGA, and EGA. By the time this is being written, it is highly unlikely that anybody is using an MDA, CGA, or EGA monitor anymore. VGA is how the monitor will display until the OS is loaded with whatever video drivers are being used.

The keyboard parameter typically lets you state that you have one or you don't.

Most CMOS Setup programs provide for two floppy disk drives: Drive A and Drive B. In general, most computers today only have one floppy diskette drive, but a second drive can be added. Sometimes CMOS will allow configuration for which of the two drives is designated as Drive A and which is designated as Drive B. In addition, the drive capacity (floppy drive type) can be selected as one of: 360K (5.25-inch), 720K (3.5-inch), 1.2MB (5.25-inch), 1.44MB (3.5-inch), and 2.88MB (3.5-inch). It is highly likely that most systems have a single 1.44 MB floppy drive designated as Drive A.

More recently introduced drives of 100MB and more are not supported directly in BIOS but depend instead on a separate driver.

Hard drive configuration is, by far, the most frequent reason for entering CMOS Setup to make configuration changes. Recently, it seems that most people who configure CMOS RAM select a new type for IDE drives: AUTO. With this setting, the POST routine will attempt to identify the drive and the parameters required to successfully read the drive. Often one of the available Setup menu selections will start a routine that will recognize and set the specific hard drive parameters instead of relying on AUTO selection. Using the drive recognition program in Setup can be used if the drive being installed is not a removable hard drive that you intend to swap with other hard drives. If there is a chance that the hard drive will be swapped on a frequent basis then the AUTO selection is probably the best. Selecting AUTO will require more time in the POST at startup. Some systems offer neither a recognition utility nor the AUTO selection. These require that the drive parameters are known and entered with each disk in the system being configured by hand.

Motherboards supporting an EIDE (aka Fast-ATA) controller for hard drives will support four disks including CD-ROM drives. Older IDE (aka ATA or AT-bus) controllers may only support two hard drives. SCSI controllers are not setup from the CMOS Setup program; SCSI controllers generally allow you to enter a setup program loaded from the SCSI controller.

Older drives, typically MFM and RLL drives had a type number. The number of drives on the market quickly outstripped any ability to store the parameters for all drives permanently in CMOS. Number 47 is the user configurable type number and is sometimes labeled as "User". For most drives, you will have to manually enter the specific data (parameters) for the drive. Those parameters are, typically:

Hard Drive Parameters
Cylinders ... Number of cylinders (tracks across all surfaces)
Heads ... Number of heads
Sectors ... Number of sectors per track
Size ... Size of the hard drive in MB
WPCom ... Write Precompensation (used only for MFM and RLL drives usually 0 or 65535)
Address Mode ... LBA or CHS ( and others)

LBA mode disk parameters can, typically, be discovered with AUTO mode or automatic configuration. If you have an older BIOS, you will need a disk manager to get larger drives recognized.

If you didn't get documentation that contains the hard drive parameters for your system and drives, make sure you copy down the drive parameters before you have a problem with CMOS memory.

Advanced CMOS Setup Menu

You can fairly well count on most of the Standard CMOS Setup menu selections being consistent from system to system. Beyond that, the CMOS menus can be as varied as the number of motherboards and BIOS chips being used. Within any given generation of PC's however, it would be unusual to not find certain features somewhere else in the Setup menus.

But in fact, there is a wide disparity in what can be set or tweaked from BIOS to BIOS, from motherboard to motherboard, and there is wide disparity in the location of parameters within the menu structure. For instance, the drive settings, commonly found in the Standard CMOS setup, can be found in a peripheral sub-menu under the Advanced CMOS Setup on some systems. In general, advanced settings are settings that affect how the chipset in a computer operates.

Some large number of "advanced" parameters are simply turned on or off, and these conditions are quite often called "enabled" and "disabled" respectively.

Quick Boot -- set the Above 1MB Memory Test: If the feature is called Quick Boot, you want it "On", otherwise, if the feature is called "Above 1 MB Memory Test" then you want it "Off." The first megabyte of memory is checked for errors, automatically, but BIOS routines will check all your memory if you tell it to. Windows runs its own verification through system drivers, so the BIOS check is unnecessary.

Memory-Test Click Sound: If turned "On", the computer clicks during the memory count during boot.

Memory Parity Error Check -- If your memory is parity memory, it can be checked for errors by enabling this parameter. A ninth bit is calculated as the parity value and checked. Parity is odd and the ninth bit is set to make the addition of all 1's in a byte (plus the parity bit) equal an odd number. If the parity check reveals a number that is not odd, then the system issues an NMI (Non-Maskable Interrupt) and stops. If you have non-parity memory, turn this off (disabled).

Typematic Rate programming: Two settings to modify: typematic rate and typematic rate delay. If you can do this through the operating system or utilities, do it there, and set it as disabled in the BIOS settings stored in CMOS. Otherwise, your keyboard must support this feature. Keep reading for information on the two settings.

Typematic Rate: A keyboard adjustment to determine how quickly a character prints to screen when a key is held down. In some cases, the choice here will be "Fast" or "Slow". In other cases, the number of characters per second will be entered (15 cps is typical, usually not over 30 cps.) For Windows systems, the typematic rate can also be set through Control Panel.

Typematic Rate Delay: The typematic rate delay is the length of time between when a key is held down and when a character begins to auto-repeat. 500 nanoseconds is a typical delay. You can think of this as an "off-key" time. How fast you type determines what this value should be. Windows also allows this value to be set from Control Panel.

NumLock: PCs boot with NumLock activated. It can be toggled to start the PC with NumLock inactivated.off with this CMOS setting.

Show F1 on Error: The F1 key is now fairly commonly used to tell the system to continue to boot in spite of certain minor problems it may encounter. If the POST finds a nonfatal error, such as a missing keyboard, the POST pauses until the F1 key is pressed. This feature should be turned "On". There are some circumstances where, maybe, it should be turned "Off." For the case, for instance, that you want the machine to boot without a keyboard, though for most user applications, I can't think why that would be.

Boot Sequence: The common setting is A:, C: which tells the system to check for an operating system to load first on Drive A (floppy) and then on Drive C (hard drive) if no operating system is found on Drive A. Some systems allow the CD-ROM drive to be specified as a boot device also. And still others will allow you to include a PXE NIC. The Boot Sequence parameter allows the order to be changed to C:, A:; CD-ROM, A:, C:; C:. A:, CD-ROM and others depending on the system. SCSI may be one of the choices given certain motherboards. And some SCSI centric servers may not let you choose CD-ROM (IDE) if you choose SCSI.

Shadowed Memory is used to copy the BIOS routines for the system board, video cards, and network cards from ROM to main memory (RAM). RAM is 3 times faster or more than ROM, so shadowing can increase performance. Unfortunately, it's not so simple to use. Careful experimentation is required to ensure that there are no conflicts between the shadowed memory and memory used by some hardware devices. The status of shadowed memory can be one of these three: Disabled, Shadow, and Cache. Disabled means that the memory is not shadowed and there will be no address conflicts. Shadow means that the memory will be shadowed, but the address will not be cached. Cache means that the memory is shadowed and it can be cached. The default is disabled. For some OS's, this should be left disabled. If you received your system "ready-to-go" from somewhere, and it works "just fine", you should record what the vendor set as being shadowed so that you will know in the future. Most vendors use the "default" settings.

For Windows and other operating systems that substitute their own routines for BIOS routines, once the OS is up and running, particularly Windows NT and subsequent Windows OS's that are based on NT, it is possible that no  performance increase will be noticed.  The speed of newer flash BIOS chips may even be quicker than some DRAM.

Virus Warning: Award BIOS incorporates Trend virus detection software. Mostly this monitors the boot sector and notifies you if something tries to write to it. In general, you should leave this turned off and invest in real virus protection software. It may cause conflicts.

Numeric Processor Test: Any CPU that you are going to put into a PC today has a FPU (Floating Point Unit) processor. This should be "enabled." Older CPU's required a math co-processor that was on a separate chip.

Floppy Drive Seek at Boot: I leave it turned on. Some say turn it off if you are not going to use the floppy drive. Some say it will preserve the floppy drive. Eah. I don't think it makes any difference and I occasionally use the floppy drive.

Boot Sequence
Controls the order in which the BIOS looks for a bootable device on start-up. Depending on your hardware, there may be a variety of options available here, including booting off the ZIP drive or LS-120 (if your BIOS supports this). Most users have this set to A, C. This makes the system look at the A: drive first for a system disk before going to the hard drive. If you are using SCSI drives, the set to A, SCSI.

Bootup CPU Speed: Bypasses some system checks. If you're in that much of a hurry set it HIGH. If you have problems, set it back to LOW.

External Cache Memory: If the system contains L2 cache, enable its use. If the system does not contain L2 cache, then disable this. If this is enabled and there is no L2 cache memory, the system may hang. If not enabled and you have L2 cache, the L2 cache is unused.

Internal Cache Memory: Enables L1 cache on the CPU chip. If your CPU has it, enable this.

Fast gate A20 option
A20 refers to the first 64K of extended memory, known as the high memory area. This option controls whether this chunk of memory is used to control all memory above 1MB. In older systems this was traditionally handled by the keyboard controller chip. For faster performance, enable this.

Turbo Switch: Disable this. Most modern processors are not intended to be run at different speeds.

Shadow Memory Cacheable
Enable for faster performance. This copies BIOS code to system RAM for faster access. Disable if there are any problems.

Video ROM Shadow
A relic from the past. When enabled, it copies code from the video portion of your BIOS over to RAM for faster access. In old DOS games, this sped up video performance. But, with Windows, it does not help. Since Windows games use API's like DirectX to write directly to the video card bypassing BIOS, enabling this option could decrease stability of your system since games could overwrite video instructions in RAM.

Adapter ROM Shadow...
This is followed by some cryptic memory addresses. This controls whether you want to shadow the ROM on any adapter cards on your system. Because you need to know what card take what memory addresses in order to use this wisely, it is recommended that this be disabled just like Video ROM shadow.

Quick Power on Self Test
This option enables a quicker boot-up by skipping some of the internal diagnostics that would usually take place on start-up. It makes boot-up faster, but also leaves you more susceptible to errors (wince); some problems will not be detected at start-up.

IDE HDD Block Mode
Enabling this function can speed up IDE drives by allowing multiple sector read/write operations, a feature most modern IDE drives support. For Win 9x, give it a whirl. Under NT, Microsoft recommends it is disabled to prevent data corruption.

Report No FDD for Windows 95
This setting fools Windows 9x into thinking there is no floppy controller installed, thus freeing up that IRQ.

You set things ONE AT A TIME and if they don't work, you set them back. Looking for somebody to sue? Never ever do anything to any parameter in CMOS--take it to a bonifide certified technician and pay his bill. Don't do this at home, kids.

While, in the near future, things will undoubtably change, we don't expect drastic changes in the BIOS or CMOS memory for the next few years.  There are currently a significant number of BIOS chips and systems