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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 interfaces
1.Hit a particular key or key combination at a right
time to enter the BIOS setup utility
Configuring the BIOS
• Setup program interfaces
2. 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  CDROM
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 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
Boot
Step 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.”
Real life Visual of how the BIOS Works
If everything’s go,
Manager hands its
duties to the…
(BIOS)
Checks On
(Operating
System)
(Devices, Drivers,
etc.)
Checks On
Function/Work On
(Computer)
End…
• Thank you……..