Basic Input Output System B.I.O.S.

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 Presentation History

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 component A storage space Evolutionarity

A component type of component: CMOS Supplied with a battery (lithium) 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 algorithm Hardware management An interface Starting 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 BIOS can emit one “BEEP”: 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

Basic Input Output System B.I.O.S.