B.I.O.S

Basic Input Output System

Introduction to BIOS

• Basic Input / Output System (BIOS)– boot the computer by providing a basic set of

instructions– load the operating system after turning on the

computer– perform POST (Power-On Self Test)– provide set-up program for changing BIOS

parameters– provide low-level routines for the

communications between OS and hardware devices

Introduction to BIOS

• BIOS combination– BIOS program– CMOS stores BIOS program– BIOS parameter

Introduction to BIOS

• Advantages of storing BIOS in ROM

– code and data are readily available during booting

– BIOS content are not corrupted by errant applications

• BIOS hardware components

– BIOS ROM

• PC startup program (POST)

– BIOS CMOS memory

• house the configuration information of individual PC

Introduction to BIOS

• The BIOS ROM

– All BIOS are contained in ROM in old days

– BIOS is now located in EEPROM chip

• erased and rewritten by special programs

• called flash BIOS

• BIOS CMOS memory

– provide a non-volatile storage for PC’s control information

– need very little power to operate

– powered by lithium battery

BIOS chip

The BIOS Boot Process

1. The power supply sends a signal to the components in the system

unit.

2. The CPU finds the ROM chips that contains BIOS.

3. The BIOS performs the POST which checks components (e.g.

mouse, keyboard connectors and expansion card)

4. The results of the POST are compared with data in the CMOS chip.

5. The BIOS looks for the system files in floppy disk drive and hard disk.

6. The system files and the kernel of the OS load into RAM from hard disk.

The BIOS Boot Process

• Beep codes– A series of beep: BIOS program encounter

problems– One short beep: everything is normal– Errors can be indicated when video screen does

not function– Interpret the beep codes by consulting main

board menu

The BIOS Boot Process

• POST Error messages– Error messages are shown on display system– Interpret error messages by consulting owner’s

manual

Configuring the BIOS

• Setup program interfaces1.Hit a particular key or key combination at a right

time to enter the BIOS setup utility

Configuring the BIOS

• Setup program interfaces2. A BIOS setup screen is displayed.

Configuring the BIOS

• Typical key control– Incorrect settings of BIOS may lead to system

halt– Quit the setup without saving changes if we are

not sure about the changed settings– Boot sequence

• control the order in which BIOS looks for an OS on start-up

• usual sequence: floppy disk hard disk CD-ROM

Configuring the BIOS

• Typical key control– Performance tuning through BIOS settings

• BIOS settings are responsible for how the chipset is controlled.

• Chipset is the key to the overall system performance

• BIOS parameters:– Choose the optimal bus speed settings

– Enable the CPU’s internal cache

– External cache memory

– Enable system BIOS shadowing

– Quick power-on self test

– Update the BIOS

Parts of the Boot ProcessParts of the Boot Process

• Step 1: POST

• Step 2: ROM BIOS startup program searches for and loads an OS

• Step 3: OS configures the system and completes its own loading

• Step 4: User executes application software

Boot Step 1

BootStep 2

Boot Step 3

A Easy Real Life Example of the BIOS

• Imagine the BIOS is the general manager of a store. The manager has to make sure all of the employees (Drivers, devices, etc) and everything is in order for opening (Booting up). So the manager (BIOS) checks all of the employees and sees if they are in working fast enough and getting the job done. If they are then the store (Computer) is in good shape. Then the general manager goes into his office and does some paper work and turns its duties to the operating system (manager). So basically when you hear BIOS, think general manager of the computer or “store.”

Checks On

(BIOS)

Function/Work On

(Devices, Drivers, etc.) Checks On

(Computer)

If everything’s go, Manager hands its

duties to the…

(Operating System)

Real life Visual of how the BIOS Works

End…End…• Thank you……..