Basic Input/Output Basic Input/Output System (BIOS)System (BIOS)

5.15.1 Introduction to BIOSIntroduction to BIOSBasic 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

5.15.1 Introduction to BIOSIntroduction to BIOSBIOS combination

BIOS program

CMOS stores BIOS program

BIOS parameter

5.15.1 Introduction to BIOSIntroduction to BIOSAdvantages of storing BIOS in ROM

code and data are readily available during booting

BIOS content are not corrupted by errant applications

BIOS hardware componentsBIOS ROM

PC startup program (POST)

BIOS CMOS memoryhouse the configuration information of individual PC

5.15.1 Introduction to BIOSIntroduction to BIOSThe BIOS ROM

All BIOS are contained in ROM in old days

BIOS is now located in EEPROM chiperased and rewritten by special programs

called flash BIOS

BIOS CMOS memoryprovide a non-volatile storage for PC’s control information

need very little power to operate

powered by lithium battery

5.15.1 Introduction to BIOSIntroduction to BIOSBIOS chip

5.25.2 The BIOS Boot ProcessThe BIOS Boot Process1. 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.

5.25.2 The BIOS Boot ProcessThe BIOS Boot Process5. 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.

5.25.2 The BIOS Boot ProcessThe BIOS Boot ProcessBeep 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

5.25.2 The BIOS Boot ProcessThe BIOS Boot ProcessPOST Error messages

Error messages are shown on display system

Interpret error messages by consulting owner’s manual

5.35.3 Configuring the BIOSConfiguring the BIOSSetup program interfaces

1. Hit a particular key or key combination at a right time to enter the BIOS setup utility

5.35.3 Configuring the BIOSConfiguring the BIOSSetup program interfaces

2. A BIOS setup screen is displayed.

5.35.3 Configuring the BIOSConfiguring the BIOSTypical 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 sequencecontrol the order in which BIOS looks for an OS on start-up

usual sequence: floppy disk hard disk CD-ROM

5.35.3 Configuring the BIOSConfiguring the BIOSTypical key control

Performance tuning through BIOS settingsBIOS 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

CMOS Setup CMOS Setup • Main menu Main menu

– Access to all submenusAccess to all submenus

Standard CMOS FeaturesStandard CMOS Features• Clock, hard drives, floppy drivesClock, hard drives, floppy drives

SoftMenu SetupSoftMenu Setup

Normally set to Default or Auto for allNormally set to Default or Auto for all

Advanced FeaturesAdvanced Features

POST, boot orderPOST, boot order

Power ManagementPower Management

Use to enable/disable power-saving featuresUse to enable/disable power-saving features

PnP/PCIPnP/PCIRarely need to manipulate on today’s PCsRarely need to manipulate on today’s PCs

Set PasswordSet Password

Locks access to CMOS settingsLocks access to CMOS settingsPrevents non-techs from changing key settingsPrevents non-techs from changing key settings