B.I.O.S.

Basic Input Output System

Plan of the presentation Introduction

Presentation History

BIOS: a hardware A component A storage space Evolutionarity

BIOS: a firmware BIOS an algorithm Hardware management An interface Starting diagram

Future

Introduction

PresentationHistory

Presentation Basic Input Output System ou BIOS

package of basic function (read, write, …)

contents in the read-only memory (ROM) of the motherboard

Term used for the whole of the “firmware” or “microcodes” of a motherboard

Intermediary between the Hardware and the Operating System

History 1981 : program code that makes up the BIOS

Before the 90s so BIOSes were held on ROM chips

○ could not be altered○ As its complexity and need for updates grew

Between 90s and 2005 BIOS firmware was subsequently stored on EEPROM or flash memory

In 2006, the first systems supporting a Serial Peripheral Interface appeared, and the BIOS flash moved again

In the newest systems, the core of this code remains functionally identical to that in decades-old machines

BIOS: a hardware

A componentA storage spaceEvolutionarity

A component type of component: CMOS

Particularity: low energy consumption

Directly implant on a motherboard or a peripheric card

ROM (90s)

○ Manufactured by the designer of Mother-Board

○ Can’t be altered

PROM / EPROM / EEPROM (90 to Nowadays)

○ A first version was implement in

○ Manufacture release update

○ Can be update

Supplied with a battery (lithium) Save personnal change (except Rom)

A storage space BIOS is a storage space:

stored in a permanent way○ lithium battery○ low energy consumption

a memory of reduced size○ No more than 100 bytes

contains:○ parameters○ functions

Evolutionarity computer system can contain several BIOS firmware chips

plug-in adapter cards such as SCSI, RAID, Network interface cards, and video boards include their own BIOS

Add-in cards usually only require such an add-in BIOS if they: Need to be used prior to the time that the operating

system loads Are not sufficiently simple, or generic in operation to be

handled by the main BIOS directly

Evolutionarity

Older operating systems such as DOS may continue to ake use of the BIOS to handle input and output

most modern operating systems interact with hardware devices directly

these add-in BIOSs are still called by modern operating systems, in order to carry out specific tasks

BIOS: a firmware

BIOS an algorithmHardware managementAn interfaceStarting diagram

BIOS an algorithm FSB (Front side bus):

that carries all electronic signal information between the processor (CPU) and the random access memory (RAM)

Unit: MHz

DRAM clock (Dynamic random

access memory): Fequence of the RAM

Hardware management

Identify and initiate component hardware

Most important role to load the operating system.

The BIOS provides first instructions of the microprocessor when you turn on your computer

Hardware management Some of the other common tasks that the BIOS performs

include: A power-on self-test (POST) for all of the different

hardware components Activating other BIOS chips on different cards installed in

the computer Managing a collection of settings for the hard disks,

clock...

The BIOS is special software that interfaces the major hardware components of your computer with the operating system.

An interface To enter the CMOS Setup, you must press a certain key or

combination of keys during the initial startup sequence

A set of text screens with a number of options appears.

Common options include: System Time/Date Boot Sequence Plug and Play Mouse/Keyboard Drive Configuration Memory Security Power Management Exit

Starting diagram During the boot sequence, the BIOS is doing a remarkable amount of work to get

your computer ready to run.

When you turn on your computer, the BIOS does several things. This is its usual sequence: Check the CMOS Setup for custom settings Load the interrupt handlers and device drivers Initialize registers and power management Perform the power-on self-test (POST) Display system settings Determine which devices are bootable Initiate the bootstrap sequence

BIOS can emit one “BEEP”: end of the POST the computer will play an audible 'BEEP' If the POST completed successfully without detecting any problems with then

system will play a single short beep if a problem is detected before the BIOS initializes the video card, or a video

card is not present or not detected then the BIOS will play several 'BEEPS'

Starting diagram

Future

Future Extensible Firmware Interface (EFI)

EFI is intended as a significantly improved replacement of the old legacy BIOS firmware interface

A lot of advantages compared with BIOS

BIOS is written in assembly language, EFI is developed in C

Future

B.I.O.S.

Basic Input Output System