CMOS Setting Specifications

The CMOS RAM must be configured with information about your system's drives and user-selected options before you can use your computer. The Setup program provided with your system is used to select the options you want to use to start your computer.

Running or Accessing the CMOS Setup Program

If you want to run the BIOS Setup program, you usually have to reboot and press a particular key or key combination during the POST. The major vendors have standardized the following keystrokes to enter the BIOS Setup in recent systems:

  • AMI BIOS. Press Delete during POST.

  • Phoenix BIOS (FirstBIOS Pro). Press F2 during POST.

  • Award BIOS (FirstBIOS). Press Delete or Ctrl+Alt+Esc during POST.

  • Microid Research (MR) BIOS. Press Esc during POST.

If your system will not respond to one of these common keystroke settings, you might have to contact the manufacturer or read the system documentation to find the correct keystrokes.

Some unique ones are as follows:

  • IBM Aptiva/Valuepoint or Thinkpad. Press F1 during POST or while powering on the system.

  • Toshiba notebook/laptop. Press Esc while powering on the system; then press F1 when prompted.

  • Older Phoenix BIOS. Boot to a safe mode DOS command prompt, and then press Ctrl+Alt+Esc or Ctrl+Alt+S.

  • Compaq. Press F10 during POST.

After you are at the BIOS Setup main screen, you'll usually find a main menu allowing access to other menus and submenus of different sections or screens.

Using the Intel D845PEBT2 D845PEBT2 motherboard as an example (one of Intel's recent motherboards), let's go through all the menus and submenus of this typical motherboard. Although other motherboards might feature slightly different settings, most are very similar.

BIOS Setup Menus

Most modern BIOSs offer a menu bar at the top of the screen when you're in the BIOS Setup that controls navigation through the various primary menus. Typical menu bar offers the choices:

  • Maintenance - Specifies the processor speed and clears the setup passwords. This menu is available only in Configure mode, set by a jumper on the board.
  • Main - Allocates resources for hardware components.
  • Advanced - Specifies advanced features available through the chipset.
  • Security - Specifies passwords and security features.
  • Power - Specifies power management features.
  • Boot - Specifies boot options and power supply controls.
  • Exit - Saves or discards changes to the setup program options.

Choosing each of these selections takes you to another menu with more choices. The following sections examine all the choices available in a typical motherboard, such as the Intel D845PEBT2.

Maintenance Menu

The Maintenance menu is a special menu for setting the processor speed and clearing the setup passwords. Older motherboards used jumpers to configure the processor bus speed (motherboard speed) and processor multiplier. Most newer boards from Intel and others now offer this control via the BIOS Setup rather than moving jumpers.

In the case of Intel, one jumper still remains on the board called the configuration jumper, and it must be set to Configure mode for the Maintenance menu to be available. Setup displays this menu only if the system is set in Configure mode.

To set Configure mode, power off the system and move the configuration jumper on the motherboard from Normal to Configure. Because this is the only jumper on a modern Intel board, it is pretty easy to find.

When the system is powered back on, the BIOS Setup automatically runs, and you will be able to select the Maintenance menu. After making changes and saving, power off the system and reset the jumper to Normal mode for normal operation.

If a user forgets his password, all he has to do is set the configuration jumper, enter the Maintenance menu in BIOS Setup, and use the option provided to clear the password. This function doesn't tell the user what the password was; it simply clears it, allowing a new one to be set if desired.

This means the security is only as good as the lock on the system case because anybody who can get to the configuration jumper can clear the password and access the system. This is why most better cases come equipped with locks.

Main Menu

The standard CMOS Setup menu dates back to the 286 days, when the complete BIOS Setup consisted of only one menu. In the standard menu, you can set the system clock and record hard disk and floppy drive parameters and the basic video type. Newer BIOSs have more complicated setups with more menus and submenus, so the main menu often is fairly sparse compared to older systems.

The main menu in a modern system reports system information such as the BIOS version, the processor type and speed, the amount of memory, and whether the memory or cache is configured for ECC functionality. The main menu also can be used to set the system date and time.

ECC stands for error correcting code, which is the use of extra bits on the memory modules to detect and even correct memory errors on-the-fly. For ECC to be enabled, more expensive ECC DIMMs would have to be installed in the system.

Note that all DIMMs would need to be ECC versions for this to work; if even one is non-ECC, ECC can't be enabled. I highly recommend purchasing ECC memory and enabling this function because it makes the system much more fault tolerant and prevents corrupted data due to soft errors in memory.

Random memory errors can occur at the rate of up to 1 bit error per month for every 64–256 megabytes installed. ECC ensures that these errors don't creep into your data files, corrupt the system, or cause it to crash. Be sure to check whether your motherboard supports ECC memory before purchasing memory.

You can install ECC memory in a non-ECC-capable board, but the ECC functions will not work. Also make sure you are aware of the memory requirements for your board.

Don't try to install more memory than the board supports, and be sure the modules you use meet the specifications required by the board. See the documentation for the motherboard for more information on the type and amount of memory that can be installed.

Most older BIOSs report memory as base and extended memory instead of as a single value. Base memory is typically 640KB and sometimes is called conventional memory. Extended memory is that which is beyond the first megabyte in the system.

You can't change any values in the memory fields; they are only for your information because they are automatically counted up by the system. If the memory count doesn't match what you have installed, a problem has likely occurred with some of the memory: It is defective, is not fully seated or properly installed, or is a type that is incompatible with your system.

Security Menu

Most BIOSs include two passwords for security, called the supervisor and user passwords. These passwords help control who is allowed to access the BIOS Setup program and who is allowed to boot the computer. The supervisor password is also called a setup password because it controls access to the setup program.

The user password is also called a system password because it controls access to the entire system. If a supervisor password is set, a password prompt is displayed when an attempt is made to enter the BIOS Setup menus.

When entered correctly, the supervisor password gives unrestricted access to view and change all the Setup options in the Setup program. If the supervisor password is not entered or is entered incorrectly, access to view and change Setup options in the Setup program is restricted.

If the user password is set, the password prompt is displayed before the computer boots up. The password must be entered correctly before the system is allowed to boot. Note that if only the supervisor password is set, the computer boots without asking for a password because the supervisor password controls access only to the BIOS Setup menus.

If both passwords are set, the password prompt is displayed at boot time, and either the user or the supervisor password can be entered to boot the computer. In most systems, the password can be up to seven or eight characters long. If you forget the password, most systems have a jumper on the board that allows all passwords to be cleared.

This means that for most systems, the password security also requires that the system case be locked to prevent users from opening the cover and accessing the password-clear jumper. This jumper is often not labeled on the board for security reasons, but it can be found in the motherboard or system documentation.

Provided you know the password and can get into the BIOS Setup, a password can also be cleared by entering the BIOS Setup and selecting the Clear Password function. If no Clear function is available, you can still clear the password by selecting the Set Password function and pressing Enter (for no password) at the prompts.

To clear passwords if the password is forgotten, most motherboards have a password-clear jumper or switch. Intel motherboards require that you set the configuration jumper, enter the Maintenance menu in BIOS Setup, and select the Clear Password feature.

If you can't find the documentation for your board and aren't sure how to clear the passwords, you can try removing the battery for 15 minutes or so—it clears the CMOS RAM. It can take that long for the CMOS RAM to clear on some systems because they have capacitors in the circuit that retain a charge. Note that this also erases all other BIOS settings, including the hard disk settings, so they should be recorded beforehand.

Power Menu

Power management is defined as the capability of the system to automatically enter power-conserving modes during periods of inactivity. Two main classes of power management exist; the original standard was called Advanced Power Management (APM) and was supported by most systems since the 386 and 486 processors.

More recently, a new type of power management called Advanced Configuration and Power Interface (ACPI) has been developed and began appearing in systems during 1998. Most systems sold in 1998 or later support the more advanced ACPI type of power management.

In APM, the hardware does the actual power management, and the operating system or other software had little control. With ACPI, the power management is now done by the operating system and BIOS, and not the hardware.

This makes the control more centralized and easier to access and enables applications to work with the power management. Instead of using the BIOS Setup options, you merely ensure that ACPI is enabled in the BIOS Setup and then manage all the power settings through Windows 98/Me, 2000/XP, or later.

When in Standby mode, the BIOS reduces power consumption by spinning down hard drives and reducing power to or turning off monitors that comply with Video Electronics Standards Organization (VESA) and Display Power Management Signaling (DPMS).

While in Standby mode, the system can still respond to external interrupts, such as those from keyboards, mice, fax/modems, or network adapters. For example, any keyboard or mouse activity brings the system out of Standby mode and immediately restores power to the monitor.

In most systems, the operating system takes over most of the power management settings, and in some cases, it can even override the BIOS settings. This is definitely true if the operating system and motherboard both support ACPI.

Some systems feature additional power management settings in their BIOS. These options are listed in "Additional Power Management Settings" in the Technical Reference section of the DVD packaged with this book.

Boot Menu (Boot Sequence, Order)

The Boot menu is used for setting the boot features and the boot sequence (through submenus). If your operating system includes a bootable CD—Windows XP, for example—use this menu to change the boot drive order to check your CD before your hard drive.

Exit Menu

The Exit menu is for exiting the Setup program, saving changes, and loading and saving defaults. After you have selected an optimum set of BIOS Setup settings, you can save them using the Save Custom Defaults option. This enables you to quickly restore your settings if they are corrupted or lost. All BIOS settings are stored in the CMOS RAM memory, which is powered by a battery attached to the motherboard.