Basic Input/Output System (BIOS)

5.1Introduction 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

5.1Introduction to BIOS BIOS combination BIOS program CMOS stores BIOS program BIOS parameter

5.1Introduction 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

5.1Introduction 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

5.1Introduction to BIOS BIOS chip

5.2The 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.

5.2The BIOS Boot Process 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.

5.2The 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

5.2The BIOS Boot Process POST Error messages Error messages are shown on display system Interpret error messages by consulting owner’s manual

5.3Configuring the BIOS Setup program interfaces 1.Hit a particular key or key combination at a right time to enter the BIOS setup utility

5.3Configuring the BIOS Setup program interfaces 2.A BIOS setup screen is displayed.

5.3Configuring 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

5.3Configuring 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

CMOS Setup Main menuMain menu –Access to all submenus

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

SoftMenu Setup Normally set to Default or Auto for all

Advanced Features POST, boot order

Power Management Use to enable/disable power-saving features

PnP/PCI Rarely need to manipulate on today’s PCs

Set Password Locks access to CMOS settings Prevents non-techs from changing key settings