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PRESENTATION ON

COMPUTER ARCHITECTURE

Vikash Kumar .A

Ramanujam School Of Computer Science,

Pondicherry University.

BIOS AND OS LOADING

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ROM

- Learn How EverythingWorks

Read Only

Memory :

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HISTORY OF

ROM Every stored - program computer requires some formof non-volatile, or erasable, storage to store the initialprogram that runs when the computer is powered on.

BOOTSTRAPPING

BEFORE 1948 Until then it was not a stored-program computer asevery program had to be manually wired into the machine,which could take days to weeks

Then it is employed as non-volatile storage forprograms in most early stored-program computers, in ROM(Read Only Memory)

ENIAC

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In 1960S

Invent of integrated circuits Both ROM and static RAM were implemented as arraysof transistors in silicon chips

A ROM memory cell could be implemented using fewer

transistors than an SRAM memory cell, since the latterrequires a latch (comprising 5-20 transistors) to retain itscontents

In 1980S Most home PC stored a BASIC interpreter or Operating

System in ROM as non-volatile storage

Were too expensive.

Later the IBM PC XT often included magnetic diskdrives, and larger amounts of RAM, allowing them to load

their operating systems from disk into RAM,

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TYPES OF

ROMS Programmable Read - Only Memory

Erasable Programmable Read - Only Memory

Electrically Erasable Programmable Read -

Only Memory

Electrically alterable Read - OnlyMemory

Flash Memory

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PROGRAMMABLE READ - ONLY MEMORY

One-Time Programmable ROM (OTP) Programmed using a special device called a PROMprogrammer PROM can only be programmed once.

ERASABLEPROGRAMMABLE READ - ONLY

MEMORY

More than one time Programmable Can be erased by exposure to strong UltravioletLight (typically for 10 minutes or longer)

Programmed using a special device called a PROMprogrammer

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ELECTRICALLY ERASABLE PROGRAMMABLE

READ ONLY MEMORY

It is based on a similar semiconductor Entire contents (or selected banks) to be electricallyerased, then rewritten electrically.

ELECTRICALLY ALTERABLE READ ONLY

MEMORY Type of EEPROM that can be modified one bit at a time Very slow process and again requires higher voltage(usually around 12 V)

FLASH MEMORY

It is a modern type of EEPROM Can be erased and rewritten faster than ordinaryEEPROM Newer designs feature very high endurance (exceeding1,000,000 cycles)

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BIOS```

BASICINPUTOUTPUTSYSTEM

bye-ose

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BIOS It is typically placed in a ROM Chip that comes withyour MB.

It is Built-in software that determines what a

computer can do without accessing programs from a disk.

It also makes it possible for a computer to boot itself.

Many modern PCs have a Flash BIOS, which meansthat the BIOS has been recorded on a Flash Memory chip,

which can be updated if necessary.BIOS is a group of programs.

ROM is a hardware chip used to store BIOS.

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The internal power supply turns on, initializes and thentakes a few moments to generate reliable power for the restof the computer.

After a Power Good signal is received, or after the resetbutton is released and there is confirmation of reliablepower, the processor will be ready to start executing.

If not within expected parameters, the chipset will

generate a reset signal to the processor in the same fashionas if you were to touch the reset button.

This will continue until the motherboard receives a PowerGood signal from the power supply

POWER GOOD

SIGNAL

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BIOS BOOT

SEQUENCE The internal power supply turns on and it receivesthe Power Good Signal from the power supply.

The processor will be ready to start executing.

But it is suffering from amnesia; there is nothing at all

in the memory to execute.

Programmers pre-program the processor to alwayslook at BIOS ROM for the start of the BIOS boot program

At the location FFFF0h, right at the end of the systemmemory

The BIOS performs the Power-On Self Test(POST)

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POWER-ON SELF

TEST

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POST ERRORS

If there are any fatal errors, the boot process stops.

POST beep codes can be found in this area.

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AMI BEEP CODES (AMERICANMEGATRENDS)# of Beeps Error Description

1 Refresh Failure The memory refresh Circuitry is faulty

2 Parity Error Parity error in the Base (1st 64K) of memory

3 64K Base Memory Error Memory error in the base memory (1st 64K)

4 Timer Not Operational Timer 1 is not functioning (also caused by error in base memory)

5 Processor Error CPU error

6 8042 Gate A20 Failure Unable to switch to protected mode

7 Processor Exception Interrupt error The CPU on the CPU card generated an interrupt error

8 Display Memory Read/Write Error Video adapter is missing, incorrectly seated or has faulty memory

9 ROM checksum error The ROM checksum does not match that of the BIOS

10 Coms Shutdown Register Read/Write The shutdown register for coms RAM has failed

11 Cache Memory Bad The cache memory test has failed. Cache memory will be disabled. *** DO NOT

enable it ***

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AWARD BEEPCODES

Beep Code Error

1 Long 2 Short Video Card Error - Either re-seat or replace video card

Repeating beeps Memory Error - Memory is either damaged or badly seated

Repeating Hi/Low Beeps Damaged or Overheating CPU

Hi Frequency Beeps Overheating CPU

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IBM BEEPCODESBeep Code Error

1 Short Beep Normal POST, System booted OK

2 Short Beeps POST Error - Code on Display

No Beep Power supply or Motherboard error

Continuous Beep Power supply or Motherboard error

Repeating short beeps Power supply or Motherboard error

1 short, 1 long beep System board error

1 long, 2 short beeps Display adapter error (MDA/CGA)

1 long, 3 short beeps Display adapter error (EGA/VGA)

3 long beeps 3270 keyboard card

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BIOS BOOT SEQUENCE

cont The BIOS code begins its search by looking for a videocard

The BIOS begins searching for other devices thatThe floppy drive is located at 0000:7C00

The IDE/ATA hard disk BIOS will be found at C8000h If Hard Disk Will not be found by BIOS means

it shows a errorsmessage

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DISK BOOT ERROR

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BIOS BOOT SEQUENCE

cont The BIOS displays its startup screen

It will also test for Memory count-up which isdisplayed in the screen.

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CMOS~~~

COMPLEMENTARY

METALOxide Semiconductor

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CMOSHardware that is common, necessarybut may change

RAM, hard drives, floppy drives, serial and parallel

ports

Programs are stored on the system BIOS chip, whilethe changeable data is stored on a CMOS chip

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CMOS SETUP UTILITIES

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CMOS SETUPPROGRAM

The data on the CMOS chip can be accessed andupdated through the CMOS setup program.

American Megatrends (AMI), Award software, andPhoenix Technologies are the main manufacturers of

BIOS.

The CMOS setup can be accessed when the systemboots, but there are different ways of doing that

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ACCESSING THE CMOS

AMI and Award Press DEL

Phoenix Press Ctrl-Alt-Esc or F2

Other possible key combinations are:

DEL, Ctrl-Alt-Ins, Ctrl-A, Ctrl-S, Ctrl-F1, F2, F10

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CMOS SETUP

The floppy drive, hard drive, and the date/time settingscan be changed using the standard CMOS setup

Modern computers provide extra CMOS settings formemory management, password and booting options, error

handling, and power management

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CMOS SETUP

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CMOS SETUP

The following CMOS setting options areavailable:

CPU soft menu Enables you to set the voltageand multiplier settings on the motherboard for the CPU.

Advanced BIOS feature Used for selecting bootoptions.

Advanced chipset features Deals withextremely low-level chipset functions.

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CMOS SETUP

The following CMOS setting options areavailable (continued):

Integrated peripherals Allows you to configure,enable, or disable onboard ports.

Power management setup Used to setup powermanagement settings for the system.

PnP/PCI configurations Used for assigning IRQsto certain resources

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CMOS SETUP

Other options include:

Load Fail-Safe Defaults: used when low-levelproblems occur

Load Optimized Defaults: sets the CMOS to thebest possible speed and stability of the system

Set Password

Save and Exit Setup

Exit Without Saving

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SOFT MENU

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ADVANCED BIOSFEATURES

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INTEGRATEDPERIPHERALS

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POWER MANAGEMENTSETUP

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PLUG AND PLAYCONFIGURATIONS

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CMOS PASSWORD

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PHOENIX BIOS SETUP

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OLDER AWARD CMOSSETUP

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CMOSMAINTENANCE

Common causes of loosing CMOS data are Battery run out, dirt, faulty power supply, electrical

surges, and chip creeps

The CMOS settings can be checked by memorizingsettings, using Optimized defaults, and backing up a

copy of the CMOS

To backup your CMOS to a floppy, use a third-party programsuch as cmossave.zip

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BATTERY

Since the data stored on a CMOS chip can besaved, power is required when the computer isturned off

Power is supplied by a battery on the

motherboard

Batteries are mounted in one of three ways:

External battery (now obsolete)

Onboard battery

Built-in battery (built into the CMOS chip and verycommon today)

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CLUES TO A WEAKBATTERY

Clock in Windows beginsto slow down

System keeps losingCMOS data when youturn it off

If you have an externalbattery, check it with avoltmeter (3.6 or 6 volts)

If a built-in battery dies,

replace the motherboard(seldom happens)

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OS BOOTSEQUENCE Once the BIOS finishes what it needs to do, it begins

searching for a drive to boot an operating system

Most are set to first look for a bootable floppy disk, and ifone is not found then proceed to a hard disk, which isusually the C: drive. Some BIOS's permit you to boot from

your CD-ROM drive

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If it is searching a hard disk, it looks for a master bootrecord at cylinder 0, head 0, sector 1, the first sector on thedisk.

Once the boot sector is found and its contents or data

verified, the BIOS starts the process of booting theoperating system by using the information in the boot sector

If a Master Boot Record is found, it is read into memory atlocation 0000:7c00

The small program in the Master Boot Record will attemptto locate an active (bootable) partition in the hard drivespartition table

If such a partition is found, the boot sector of thatpartition is also read into memory at location 0000:7C00

OS BOOT SEQUENCEcont

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Keep in mind that each operating system has its ownboot sector format

The next step involves the small program in the boot

sector locating the first part of the operating system's kernelloader program

If no boot device of any type can be found, the systemwill display an error message and stop

No boot device


OS BOOT SEQUENCE

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STEP

1:

OS BOOT SEQUENCE

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OS BOOT SEQUENCEcont STEP 2:

OS BOOT SEQUENCE

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STEP

3:

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SINGLE OS

BOOT PROCESS

SINGLE OS BOOT

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POWER ON

BIOSCONTROL

BIOSOPERATION

MBR Program(Booting Process)

Executing first sector of disk

Partition Table to find activePartition Partition

PBR locate system file

Win98 io.sys

Win XPs ntoskrnl

SINGLE OS BOOTPROCESS

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MULTIPLE OS BOOT

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Multiple OS Boot Process

Microsoft Way Non-Microsoft Way

MULTIPLE OS BOOTPROCESS

Mi ft W

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BIOS Control

MBR looks into partitiontable

PBR of activepartition

But Win98 installed (altered toWin Xp)

No Win98 contain( file likeio.sys)

It contain the

ntldr

Ntldr looks into boot.ini (loadsthe OS)

If Win 98 select then it looks for

bootsect.dos

Microsoft Way

N Mi ft W

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Non-Microsoft Way

In this system, installing multiple OSes isconceptually simple

First make as many Primary Partitions and LogicalPartition as you want

Then set the status of one of the Partition asActive, and install on OS. After this set the statusof that partition as Hidden (or Inactive ) and setanother Partition as Active and install another OS

N Mi ft W

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Non-Microsoft Way

3 points Displays a list of all OSes present in both Primary andLogical Partitions.

When a user select one, Boot Loader makes the

Partition of that OS as Active and passes the control to it

Then, the Boot Sector of the corresponding OS takescontrol and loads the OS. This Boot Sector may be PBR of aPrimary Partition or LEBR of a Logical Extended Partition.

By this way, each OS remains independent of each other.

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Thank

bios 21.10.2009)

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