Technical The BIOS and CMOS BIOS Features Set-up

BIOS Features Set-up

All advanced BIOS features set-up options are described on this page.

Virus Warning

During and after the system boots up, any attempt to write to the boot sector or partition table of the hard disk will halt the system and causes a message to flash on the screen. This field is really intended for a DOS only operating a computer and should be disabled when running Windows 9x operating systems which do not trap INT 13. Some BIOS do not have an option to disable this field and a utility such as twk153b.zip may have to be used. This feature of the BIOS is not supported by UDMA 66 HDD or SCSI HDD or any drives connected to cache controllers.
It is important that the option is disabled prior to installing any operating system on the computer as the Virus Warning may prevent proper installation. Also hard drive utilities such as defragmenter, will be prevented from performing correctly with the option enabled.

Enabled: Activate automatically when the system boots up causing a error message to appear when anything attempts to access the boot sector or hard disk partition table.
Disabled: No warning message appears when anything attempts to access the boot sector or hard disk partition table.

CPU Internal Cache

This field enables (speed up memory access) or disables the cache function on board the CPU. The option is really only useful disabled, if the user is trying to determine if it is a problem or fault on the cache that is preventing normal operation. Can also useful when over clocking, if the cache is suspected as being the cause of a system not being able to run faster than the recommended CPU speed.

Enabled: Enable cache function.
Disabled: disable cache function.

External Cache

This field enables (speed up memory access) or disables the level two (L2) cache function on the motherboard or CPU on the Pentium III. The option is really only useful disabled, if the user is trying to determine if it is a problem or fault on the cache that is preventing normal operation. Can also useful when over clocking, if the cache is suspected as being the cause of a system not being able to run faster than the recommended CPU speed.

Enabled: Enable cache function.
Disabled: disable cache function.

CPU L2 Cache ECC Checking

This field sets the option for the L2 cache ECC checking function and may not be available on all motherboards. This will detect and correct single-bit errors in data stored in the L2 cache and detect but not correct, double-bit errors. ECC checking stabilizes the system. Enabling ECC checking reduces system performance but the difference is small, if at all. The stability and reliability achieved via ECC checking is worth the added overhead.

Enabled: Enables the L2 cache's ECC checking function
Disabled: Disables the L2 cache's ECC checking function.

Processor Number Feature

This field sets the option for reading the Pentium III serial number by external programs. Enable this if a secure transactions requires such a feature. This field will only appear a Pentium III processor is installed.

Enabled: External programs can read the Pentium III serial number
Disabled: The Pentium III serial number is not available to external programs.

Quick Power on Self Test

This field enables quick POST. The BIOS will shorten or skip some check items during POST to speed up POST after powering on the computer.

Disabled: Normal POST.
Enabled: Enable quick post.

Boot Sequence

This field enables the user to set the sequence in which the BIOS will search for an operating system. To ensure the shortest booting time possible, select the hard disk that contains the operating system as the first choice. Normally, that would be drive C but if using a SCSI hard disk, then select SCSI.
A bootable CD is a disc that contains a bootable image an ISO 9660 file that is an exact representation of a floppy or hard drive from which a user can boot the system. The options are:

A, C, SCSI
C, A, SCSI
C, CD-ROM, A
CD-ROM, C, A
D, A, SCSI (only when using at least 2 IDE hard disks)
E, A, SCSI (only when using at least 3 IDE hard disks)
F, A, SCSI (only when using 4 IDE hard disks)
SCSI, A, C
SCSI, C, A
A, SCSI, C
LS/ZIP,C
C only.

Some BIOS may offer different options in future releases or do not support all of the options above. The following options may be found:

First Boot Device: set the first device from which the BIOS will attempt to load the operating system
Second Boot Device: set the second device from which the BIOS will attempt to load the operating system
Third Boot Device: set the third device from which the BIOS will attempt to load the operating system
Boot Other Device: This feature determines whether the BIOS will attempt to load an OS from the Second or Third Boot Device if it fails to load one from the first boot device.

It is possible to boot to different operating systems if each is contained on a different hard drive, by changing the search sequence, or first boot device.

Swap Floppy Drive

This field option allows the user to determine whether to enable Swap Floppy Drive or not.

Enabled: The BIOS will swap floppy drive assignments so that floppy drive A becomes floppy drive B and drive B becomes drive A under DOS.
Disabled: The assignment of floppy drive A and floppy drive B are left the same.

Boot up Floppy Seek

This field option is to determine if the BIOS will check for a floppy drive. During POST the BIOS will determine if the floppy disk drive installed is 40 or 80 track.

Enabled: The BIOS searches for floppy disk drives during booting.
Disabled: Skip search for floppy disk drive and speed up boot sequence.

Boot up Numlock Status

This option allows the BIOS to automatically enable the NUM Lock function when the system boots up.

On: The Numeric Keypad will function in the numeric mode
Off: The Numeric Keypad will function in the cursor control mode.

Gate A20 Option

This field determines how Gate A20 is used to address memory above 1 MB. The option enables whether the motherboard Chipset controls the operation of Gate A20, or the keyboard controller controls Gate A20. Setting Gate A20 to operate from the Chipset improves memory access performance above 1 MB because the Chipset is much faster in switching Gate A20 than the keyboard controller, (if my own memory serves me correctly) because of an extra pin that can address all the RAM without resorting to Segment and Offset to work out a exact memory address.
No real difference in performance will be noticed in DOS.

Fast: The A20 signal is controlled by Port 92 or Chipset specific method
Normal: The A20 signal is controlled by keyboard controller or Chipset hardware.

Typematic Rate setting

This feature enables control of the keystroke repeat rate when holding down a key continuously. If the option is disabled, continually holding down a key on the keyboard will only generate one instance. This field may no longer appear on modern motherboards.

Enabled: Enable typematic rate and typematic delay controls.
Disabled: Disable typematic rate and typematic delay programming. The system BIOS will use the default value for both fields.

Typematic Rate (Chars/sec)

This is the rate at which the keyboard will repeat the keystroke if a user holds down a key continuously, the time between displaying the second character, third character and so on. The option for this field has no effect if Typematic Rate Setting is disabled.

6 - 30: Set the speed of the typematic rate (characters per second).

Typematic Delay

This is the delay, in milliseconds, before the keyboard automatically repeats the keystroke that have been pressed continuously, the time between displaying the first character and second characters. The option for this field has no effect if Typematic Rate Setting is disabled.

250 - 1000: Set the time of the typematic delay.

Security Option

This field allows the user to limit access to the System and Set-up System is selected to protect both the system and set-up, with a password, every time the computer boots. Set-up only prompts for a password when the user calls the BIOS set-up

System: The system will not boot and access to Set-up will be denied until the correct password is entered at the prompt.
Set-up: The system will boot, but only access to Set-up will be denied until the correct password is entered at the prompt.

To enable security, select either Supervisor Password or User Password from the Main Menu and then the user will be asked to enter the password and then the user will be asked to confirm the password. To disable security, select either Supervisor Password or User Password from the Main Menu and then the user will be asked to enter the password. Do not type anything and just press Enter, it will disable security. Once the security is disabled, the system will boot and enter Set-up freely. Older motherboards have the options Set-up and Always.

PCI/VGA Palette Snoop

This field is used when multiple VGA devices operate on different buses. Each device can handle data from the CPU on each set of palette registers on every video device. This option is really only useful if a video card is used on the ISA bus and a VGA card on the PCI bus and prevents display problems after using the ISA cards. Such as MPEG overlay cards.

Enabled: This item must be set to Enabled if any ISA adapter card installed in the computer requires VGA palette snooping. If enabled the the colour palettes card can be synchronised between the PCI and VGA buses. Enable this option when when a VGA/TV converter is fitted.
Disabled: Disables the palette snooping into the graphics card frame buffer memory.

OS Select for DRAM >64 MB

This field is needed to define the operating system installed if more than 64 MB of RAM is in the system. This is because OS/2 manages memory differently to other operating systems.

Non-OS/2: If the operating system is not OS/2, then select this option.
OS/2: If the system has more than 64 MB of DRAM and running IBM OS/2 operating system, then select this option.

HDD SMART Capability

This field sets the option for using the hard disk drive SMART capability. The Self Monitoring Analysis And Reporting technology is supported by all current hard disks and allows early prediction and warning of the hard disk failing. SMART aware utilities can monitor the hard disk's condition. There is no performance disadvantages in enabling SMART capability.

Enable: HDD SMART capability is enabled
Disable: HDD SMART capability is enabled.

This field may not appear on older motherboards.

Video BIOS Shadow

This field sets the option to copy the Video BIOS to system RAM for quicker access. Shadowing improves the BIOS performance because the BIOS can now be read by the CPU through the 64-bit DRAM bus as opposed to the ROM bus. Copying the BIOS uses system RAM to hold the ROM contents. The windows operating system does not use the BIOS to access the graphics cards hardware, so no BIOS calls are made and no advantage to enabling shadowing.

Enabled: The Video BIOS will be copied to RAM. Video Shadowing can increase the video speed on older motherboards and graphics cards
Disabled: Video shadow is disabled.

C8000 ~ CBFFF Shadow / D0000 ~ DFFFF Shadow

This field option decides if the memory block of an address range will be shadowed or not. Copying the BIOS uses system RAM to hold the ROM contents. The windows operating system does not use the BIOS to access the graphics cards hardware, so no BIOS calls are made and no advantage to enabling shadowing.

Enabled: The contents of the named ROM area are written to the same address in system memory (RAM) for faster execution when using DOS
Disabled: Shadowing of the named ROM area is disabled.

Some expansion cards have their own BIOS, and would benefit from shadowing from slow ROM to faster RAM providing that DOS is the operating system. Windows operating systems do not use the BIOS to make calls to hardware and would not benefit from shadowing and would have memory reserved that would not be used.

Delay for HDD:

Some HDD require some spin-up time in order to be identified correctly. This settings specifies how long the BIOS has to wait.

Set this as low as possible to boot faster.

Report No FDD for Win95

This field enables the option to run the system without a floppy drive.

Enabled: Releases IRQ 6 to the system. It is also possible to disable the FDD Controller.
Disabled: the BIOS will not report the missing floppy drive to windows.

Standard CMOS Set-up

Chipset Set-up