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Bios

What BIOS Does • The BIOS software has a number of different

roles, but its most important role is to load the operating system. When you turn on your computer and the microprocessor tries to execute its first instruction, it has to get that instruction from somewhere. It cannot get it from the operating system because the operating system is located on a hard disk, and the microprocessor cannot get to it without some instructions that tell it how. The BIOS provides those instructions. Some of the other common tasks that the BIOS performs include:

• A power-on self-test (POST) for all of the different hardware components in the system to make sure everything is working properly.

• Activating other BIOS chips on different cards installed in the computer - For example, SCSI and graphics cards often have their own BIOS chips.

• Providing a set of low-level routines that the operating system uses to interface to different hardware devices - It is these routines that give the BIOS its name. They manage things like the keyboard, the screen, and the serial and parallel ports, especially when the

computer is booting. • Managing a collection of settings for the hard disks,

clock, etc.

• The BIOS is special software that interfaces the major hardware components of your computer with the operating system. It is usually stored on a Flash memory chip on the motherboard, but sometimes the chip is another type of ROM.

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BIOS uses Flash memory, a type of ROM.

When you turn on your computer, the BIOS does several things. This is its usual sequence:

1 - Check the CMOS Setup for custom settings 2 - Load the interrupt handlers and device drivers 3 - Initialize registers and power management 4 - Perform the power-on self-test (POST) 5 - Display system settings 6 - Determine which devices are bootable 7 - Initiate the bootstrap sequence

Configuring BIOS• To enter the CMOS Setup, you must press a

certain key or combination of keys during the initial startup sequence. Most systems use "Esc," "Del," "F1," "F2," "Ctrl-Esc" or "Ctrl-Alt-Esc" to enter setup. There is usually a line of text at the bottom of the display that tells you "Press “XxX “ to Enter Setup."

Bios Setup Utility

F1 General Help Gives the list of options available for each item

F5Previous Values Restores the values that were in place at the time the user

entered the BIOS. Useful if you can't remember what you changed, but is only valid if you have not yet rebooted.

F6 Load Fail-Safe

Defaults Loads all options with pre-set conservative values that the system whoudl be able to run with with no conflict.

F7 Load Optimized

Defaults Saves changes and reboots the system

F10 Save Returns for any sub-screen to the Main Menu.

ESC Exit Used to enter into a sub-screen which provides options for an item on a higher level menu

ENTER Select Used to enter into a sub-screen which provides options for an item on a higher level menu

+ / - PU/PD

Value Used to toggle up and down the available options for a particular item

Function Command Description

Options in Bios• System Time/Date - Set the system time and date • Boot Sequence - The order that BIOS will try to load the operating

system • Plug and Play - A standard for auto-detecting connected devices;

should be set to "Yes" if your computer and operating system both support it

• Mouse/Keyboard - "Enable Num Lock," "Enable the Keyboard," "Auto-Detect Mouse"...

• Drive Configuration - Configure hard drives, CD-ROM and floppy drives

• Memory - Direct the BIOS to shadow to a specific memory address • Security - Set a password for accessing the computer • Power Management - Select whether to use power management,

as well as set the amount of time for standby and suspend • Exit - Save your changes, discard your changes or restore default

settings

Extra Options• Power On After AC Failure -> It is an option in the bios of most ATX Mb's. They have

an option for "Power State After AC Loss" -- and the options are, "On", "Off", "Last State".

• AGP Driving Control -> This BIOS function allows you to adjust the control of the AGP driving force. It is usually set to Auto by default, thereby allowing the chipset to assume control and automatically adjust the AGP driving force to suit the installed AGP card.

• Floppy Mode 3 Support -> We can see this option in every bios but most uses iin Japanees computer for 1.2MB 3.5 formatted discs so useless for us can be said.

• Virus Warning -> Some BIOS manufacturers have put Virus Protection in their products. When installing Windows 95, Setup needs to write to the DOS Boot Record. The same is true for Windows 98, except when upgrading from Windows 95. If the BIOS Virus Warning is still Enabled, Setup will fail just after accepting the License agreement.

• The solution should be simple.Just Disable the Virus Warning via the CMOS SETUP before installing Windows 95/98.There are however BIOSs where this is not possible!

• PCI Latency Timer -> PCI latency timers are a mechanism for PCI bus-mastering devices to share the PCI bus fairly. "Fair" in this case means that devices won't use such a large portion of the available PCI bus bandwidth that other devices aren't able to get needed work done.

• Boot Other Devices -> in this option you can choose your boot places in an order for example if you choose Hard Disk, CD-ROM and SCSI, your system if can’t seethe

hard disk then it will open from cd-rom with this option. • Swap Floppy Drive -> A useful feature for those machines that use two floppy

drives, when enabled this swaps the A: and B: drives. This enables you to change the bootable floppy without having to open the case and switch the cable.

• VGA Palette Snooping ->This BIOS feature determines if your graphics card should allow VGA palette snooping by a fixed function display card. It is only useful if you use a fixed-function display card that requires a VGA-compatible graphics card to be present.

• It is recommended that you disable this feature if you do not use any fixed-function display card like a MPEG decoder card.

Refreshing Bios

Refreshing Bios means clearing the CMOS instructions cause the Bios values hold in there with this way you can refresh Bios values.

If you want to clear CMOS, you must go on motherboard and press the “CMOS clear” or “CLR RTC” bridge with a jumper then you will clear the Bios options…

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