Module 2Module 2

How Computers WorkHow Computers Work

Basic Functions of an Operating Systems

• Input – recognizing input from the keyboard or mouse

• Processing –- manipulating data according to the user's

instructions

• Output – sending output to the video screen or printer

• Storage – keeping track of files for use later; examples of

storage devices include floppy disks and hard drives.

Bootstrap

• For an operating system to run, it must be loaded into the

computer's Random Access Memory (RAM).

• When a computer is first turned on, it launches a small program

called the bootstrap loader that is located on the BIOS chip on

the motherboard.

• The bootstrap's primary functions are to test the computer's

hardware and to locate and load the operating system into

RAM.

Power-On Self Test

• To test the computer's hardware, the bootstrap program runs a program

called power-on self-test or POST.

• In this test, the computer's Central Processing Unit (CPU) checks itself

first and then checks the computer's system timer.

• The POST checks the Random Access Memory (RAM) by writing data to

each RAM chip and then reading that data. Any difference indicates a

problem.

• If the POST finds errors, it sends a message to the computer monitor. If

the POST finds errors that cannot be displayed on the monitor, it sends

errors in the form of "beeps."

• The POST sends one beep and the screen begins to display OS loading

messages once the bootstrap has determined that the computer has

passed the POST.

Generic Cold Boot Sequence

Desktop / Tower ModelsDesktop / Tower Models

PowerFloppy disk drive

CD-ROM drive Hard disk drive

LEDs NIC

Video card Audio card Parallel portSerial portMouse Port

Tower ModelsTower Models

Power SuppliesPower Supplies

Converts AC to DC Converts AC to DC Typically 250 –300 wattsTypically 250 –300 watts ATAT

P8 & P9 connectorP8 & P9 connector 12 pin12 pin +5, -5, +12, -12+5, -5, +12, -12

ATXATX P1 connectorP1 connector 20 pin (keyed)20 pin (keyed) +3.3,+5, -5, +12, -12+3.3,+5, -5, +12, -12

Cooling SystemsCooling Systems

The power supply fan helps The power supply fan helps prevent the computer prevent the computer components from components from overheating by maintaining overheating by maintaining airflow in the case. airflow in the case.

Overheating is a critical Overheating is a critical problem that can cause a problem that can cause a computer system to computer system to malfunction or fail. malfunction or fail.

A heat sink is made of a A heat sink is made of a material that absorbs the material that absorbs the heat generated. heat generated.

Motherboards

• System board / main board is crucial because it is the nerve

center of the computer system. Everything else in the system

plugs into it, is controlled by it, and depends on it to

communicate with other devices on the system.

• It generally houses the CPU, the controller circuitry, the bus,

RAM, expansion slots for additional boards, and ports for

external devices. In addition, it contains the CMOS and other

ROM BIOS and support chips providing varied functionality.

Motherboard Form Factors

• Describe their physical dimensions.

• AT

• ATX

• The ATX motherboard is similar to the Baby AT

motherboard, except for a number of important

enhancements. Most new systems come with the ATX

motherboard form factor.

Motherboard Components

• The major components on the motherboard include:

• chipset – interconnects all the devices on the motherboard

• CPU socket

• expansion sockets

• I/O support

• BIOS

• RAM sockets

• power supply socket

• CMOS chip

• dip switches and jumpers

• memory cache

The MotherboardThe Motherboard

The MotherboardThe Motherboard

The MotherboardThe Motherboard

The Motherboard

Power Supply

Hard (C) Drive

Floppy (A) Drive

CD (D) Drive

Inside the Computer

Video Card

Sound Card

Motherboard

Back Plane Card

Processor

RAM Speaker

DIMM memory slots

ISA slot joystick connector

IDE connectors

PCI slots hard drive

CD Drive

power connector

Floppy connector

printer connector

Mouse and keyboard connector

USB ports

processor (ZIF) socket

chipset

AMR slot

AGP slot

Expansion SlotsISA slot

PCI slots

AMR slot

AGP slot

ISA – Industry Standard Architecture

AMR – Audio/Modem Riser

AGP – Accelerated Graphics Port

PCI – Peripheral Component Interconnect

Dual Processor Motherboard DIMM memory slot

IDE connectors

PC bus slots

hard drive

CD Drive

power connector

Floppy connector

system board IC

VESA slot

keyboard connector

ISA slots

PCI slot

COM 1 COM 2 parallel port PRT 1

SIMM memory slots

processor (ZIF) socket

system RAM

IDE connectors

hard drive

CD Drive

Floppy connector

System board IC

Expansion slots

ISA slot

PCI slotsAMR slot AGP slot

PS/2 or Mini-Din

keyboard

mouse

USB

Com 1

Com 2

parallel port/PRT 1

game port

speaker

line-in

mic

power connector

RJ-45USB

1/8” Stereo Phone Jacks

DB-15 – Serial Port

DB-9 – Com 1 and Com 2

DB-15 – Video PortPS/2 - Mini Din – Keyboard and Mouse

Central Processing Units

Central Processing Unit

• Most important elements of the personal computer.

• On the motherboard, the CPU is contained on

a single integrated circuit called the microprocessor.

• The computer will not run without a CPU.

• Often referred to as the brains of a computer, the CPU contains

two basic components:

• Control unit

• Arithmetic/Logic Unit (ALU)

Control Unit

• Instructs the rest of the computer system on how to follow a

program's instructions.

• It directs the movement of data to and from processor

memory.

• The control unit temporarily holds data, instructions, and

processed information in its arithmetic/logic unit.

• In addition, it directs control signals between the CPU and

external devices such as hard disks, main memory, I/O ports,

etc.

Processor Speed

• CPU descriptions as Pentium 133, Pentium 166, or Pentium 200 are

well known. These numbers are specifications that indicate the

maximum (reliable) operating speed at which the CPU can execute

instructions.

• The CPU speed is not controlled by the microprocessor itself, but by

an external clock located on the motherboard.

• The speed of the processor is determined by the frequency of the

clock signal. Typically expressed in megahertz (MHz), and the higher

the number, the faster the processor.

BIOS ROM

• The basic input/output system (BIOS) contains the instructions and data in the ROM chip that control the boot process and the computer hardware.

• BIOS is sometimes called firmware.

• The ROM chip that contains the firmware is called the ROM BIOS chip, ROM BIOS, or simply BIOS.

AGP

Expansion Cards

Network card

Modem card

Sound card

Video card

Expansion Slots

• Sockets, are receptacles on the computer motherboard that accept

printed circuit boards. They allow additional devices to be added.

• Examples include video cards, I/O cards, and

sound cards.

• Common expansion slots:

• Industry Standard Architecture (ISA ) – 8 MHz, 16-bit

• Peripheral Component Interconnect (PCI ) – 33 MHz, 32 and 64-

bit

• Accelerated Graphics Port (AGP) - video adapters – 32-bit

Riser Cards

Riser card

CNR

AMR

Riser Cards

System Buses

RAM – Random Access Memory (SIMMS / RAM – Random Access Memory (SIMMS / DIMMS / RIMMS)DIMMS / RIMMS)

RAM – Random Access Memory (SIMMS / RAM – Random Access Memory (SIMMS / DIMMS Installation)DIMMS Installation)

Cache MemoryCache Memory

• L1 cache is located on the CPU.• L2 cache is located between the

CPU and DRAM.• L1 cache is faster than L2 because

it is located within the CPU and runs at same speed as the CPU.

• It is the first place the CPU looks for its data.

• If data is not found in L1 cache, the search will then continue with L2 cache, and then on to main memory.

• COASt modules are used to provide cache memory on many Pentium-based systems.

Monitors

• Computers are usually connected to a display, also called a

monitor.

• Some key monitor-related terms are: pixels, refresh rate,

resolution, and size. Measure screen size diagonally.

• Pixels – Are picture elements. The screen image is made of pixels

(tiny dots), which are arranged in rows across the screen. Each

pixel consists of three colors: red, green, and blue (RGB).

• Dot pitch – A measurement of how close together the phosphor

dots are on the screen. The finer the dot pitch, the better image

quality (measured in millimeters).

• CRT – Cathode Ray tube

• LDC – Liquid Crystal Display

• Cable technology - VGA and DVI are the two most common.

• Viewable area (usually measured diagonally)

• Aspect ratio and orientation (landscape or portrait)

• Maximum resolution

• Dot pitch - Refresh rate - Color depth

• Amount of power consumption

Display Technology

Dot PitchDot Pitch

Refresh Rate, Measured in Hertz (Hz)Refresh Rate, Measured in Hertz (Hz)

Changing Your Screen ResolutionChanging Your Screen Resolution

CRTCRT

A cathode-ray tubeA cathode-ray tube is a special-purpose is a special-purpose electron tube in which electrons are electron tube in which electrons are accelerated by high-voltage anodes, accelerated by high-voltage anodes, formed into a beam by focusing electrodes, formed into a beam by focusing electrodes, and projected toward a phosphorescent and projected toward a phosphorescent screen that forms one face of the tube. screen that forms one face of the tube. The beam of electrons leaves a bright spot The beam of electrons leaves a bright spot wherever it strikes the phosphor screen. wherever it strikes the phosphor screen.

Video Card

video BIOS

video controller IC

video RAM

PortsPorts

USBDB9

COM

Ports

Firewire

DB25--parallel

SCSI

Mini-DIN

Game Port-DB15

PORTS

I /O Ports

• All peripheral devices that connect to the computer such as printers,

scanners, and so on, use connectors on the back of the computer

known as ports.

• Ports:

• Serial ports – 1 bit at a time (9 pin male)

• Parallel ports – 1 byte at a time

• USB (Universal serial bus) – 127 devices daisy chained, hot

swappable, 450 Mbps

• Modem - RJ11 connectors

• NIC – RJ45 connectors

• Firewire – 63 devices using cable lengths up to 4.5 m, 400Mbps

Serial Ports

• A serial port can be used to connect devices that use a serial

interface such as a modem, scanner, mouse, etc.

• Generally, a PC can identify up to four serial ports, but the

typical computer contains only two, referred to as COM1 and

COM2.

• A serial port transmits data bits one after the other (serially)

over a single line.

Parallel Ports

• A parallel port is a socket on the computer that is used to

connect a printer or other peripheral device such as a portable

hard disk, tape backup, scanner, or a CD-ROM.

• The parallel port contains eight lines for transmitting an entire

byte (8 bits) across the eight data lines simultaneously.

• Parallel ports can be configured as

• LPT1 (IRQ 7)

• LPT2 (IRQ 5)

PS/2 Ports

• PS/2 keyboard or PS/2 mouse ports (Mini-DIN) are used to

connect your PC to its keyboard and mouse.

• Both ports look identical, ports are not interchangeable.

• Mouse (green)

• Keyboard (purple).

• Usually both ports are color coded or labeled to avoid any

confusion.

USB – Universal Serial BusUSB – Universal Serial Bus

127 devices127 devices Transfer rate up to 12 Transfer rate up to 12

MbpsMbps USB 2.0 up to 450 MbpsUSB 2.0 up to 450 Mbps

USB keyboardsUSB keyboards MiceMice PrintersPrinters ModemsModems ScannersScanners Digital camerasDigital cameras Digital video camerasDigital video cameras External disk drivesExternal disk drives

EIDE and SCSI Controllers

• The internal hard drive is connected to a disk controller with a

cable—a 40 pin cable.

• The hard drive and other devices can use one of two types of

interface controllers to work with the computer.

• These include the Enhanced Integrated Drive Electronics

(EIDE), and Small Computer System Interface (SCSI,

pronounced "scuzzy") connections.

EIDE Controllers

• Enhanced IDE (EIDE) is the "new and improved" Integrated

Drive Electronics (IDE) drive interface.

• Not confined to IDE's 528 MB of data, the EIDE interface can

handle up to 8.4 GB or more.

• While IDE can support only two drives, EIDE can support up to

four devices using two IDE cables.

SCSI Controllers

Small Computer System Interface

• Like EIDE, SCSI devices have the controlling electronics on each of

the drives.

• A standard SCSI interface will allow up to 7devices to be connected

to one SCSI adapter or controller. If the SCSI card is counted, it

makes eight SCSI devices.

• Such devices may include hard drives, CD-ROM drives, taped drives,

scanners, and removable drives.

• Each SCSI device in the chain, including the SCSI controller card is

given a SCSI ID number from 0 to 7; #0 for the primary boot device

(hard drive), and #7 for the SCSI controller card.

SCSI continued . .SCSI continued . .

Hard Disk Drive

• The HDD has a much larger storage capacity than the floppy

for long-term storage.

• It stores your programs and files, as well as the operating

system.

• Typically, the HDD is an internal drive that cannot be

removed from the computer.

Hard Disk Drive Components

• Disk platters, read/write heads, head actuator

assembly, spindle motor, logic/circuit board,

bezel/faceplate, configuration jumpers, and interface

connectors.

• Disk platters are the actual media on which data is

stored in the hard disk drive.

• Read/write heads are used to access the media.

The disk platters require a read/write head for each

side.

• Spindle motor which spins the platters.

Floppy Disk DriveFloppy Disk Drive

3.5”3.5” 1.44 MB storage1.44 MB storage Write ProtectWrite Protect

CD ROMCD ROM

Secondary Storage DeviceSecondary Storage Device CD-ROM Speed indicated by x CD-ROM Speed indicated by x

(multiples of 150 kbps)(multiples of 150 kbps) CR-ROM – Read OnlyCR-ROM – Read Only CD-R – Record ableCD-R – Record able CD-RW – Record able & CD-RW – Record able &

rewritesrewrites 650 – 700 MB650 – 700 MB 52x/32x/52x52x/32x/52x W /RW/RW /RW/R

DVD – Digital Video DiskDVD – Digital Video Disk

Storage Capacity 25 times Storage Capacity 25 times more than CDsmore than CDs

DVD-RDVD-R DVD-RWDVD-RW

NIC –Network Adapter CardNIC –Network Adapter Card

Network InterfaceNetwork Interface Token RingToken Ring EthernetEthernet

RJ-45RJ-45

ModemModem

uses Dial Up Network uses Dial Up Network connectionconnection

converts digital data into converts digital data into analoganalog

modulates/demodulatesmodulates/demodulates 56 Kbps 56 Kbps RJ-11 connectorsRJ-11 connectors UART chip—16550 UART chip—16550 V.92 current standardV.92 current standard

Interrupt Request

“Hey CPU wake up and process this.”

• Modern computers and operating systems owe their reliability

to the organized way in which they handle internal transactions.

• Various hardware devices, for example, may want to tell the

CPU that they have some information available that is ready for

transfer.

• The devices indicate this by making an interrupt request, or

IRQ.

• It is a general rule that IRQs CANNOT be shared.

Interrupt Request

Direct Memory Access (DMA)

• Channels allow devices to bypass the processor and directly

access the computer memory.

• Devices with a DMA channel assignment, as a result, gain the

advantage of faster data transfers.

• DMA channels are typically used by high-speed communication

devices for transferring large amounts of data at high speeds.

• Examples of such devices include sound cards, some network

cards, some SCSI cards, some disk drives, and some tape

backup drives.

DMA ChannelsDMA Channels

I /O Address

• In addition to an IRQ, computer components also need to be

assigned an I/O port number.

• An I/O port number is a memory address where data is

temporarily stored as it moves in and out of the devices.

• The I/O address is very similar to a post office box.

I /O Address

32-32-32-FF-EE-77-8

Frequently referred to I / O Addresses:

•3F8 = COM1

•2F8 = COM2

•3E8 = COM3

•2E8 = COM4

•378 = LPT1

•278 = LPT2

Laptop Computers / Batteries / LCD DisplaysLaptop Computers / Batteries / LCD Displays

PCMCIA CardsPCMCIA CardsPersonal Computer Memory Card Interface AssociationPersonal Computer Memory Card Interface Association

Type I Type I 3.3 mm3.3 mm memorymemory

Type IIType II 5.0 mm5.0 mm NIC, modem, etc.NIC, modem, etc.

Type IIIType III 10.5 mm10.5 mm Hard drivesHard drives

Docking StationDocking Station

Collection of devices:Collection of devices: MonitorMonitor AC PowerAC Power Network ConnectionNetwork Connection KeyboardKeyboard MouseMouse PrinterPrinter

Wireless Access PointsWireless Access Points

Allows computer to go Allows computer to go anywhere within a rangeanywhere within a range

Wired controller receives Wired controller receives and transmits data to and transmits data to wireless adapterwireless adapter

802.x802.x AA BB G G

Q:Q: How many devices will SCSI 1 support?How many devices will SCSI 1 support?A:A: 7 devices7 devicesQ:Q: How many devices will SCSI 2 support?How many devices will SCSI 2 support?A:A: 16 devices16 devicesQ:Q: How can I measure a monitor and what are the colors How can I measure a monitor and what are the colors

associated with a monitor?associated with a monitor?A:A: Diagonally, Red-Green-BlueDiagonally, Red-Green-BlueQ:Q: What is a warm boot?What is a warm boot?A:A: Restarting the computer, Ctrl-Alt-DelRestarting the computer, Ctrl-Alt-DelQ:Q: What is the very first thing that POST checks?What is the very first thing that POST checks?A:A: CPU then memoryCPU then memoryQ:Q: Does the external clock on the motherboard determine the Does the external clock on the motherboard determine the

speed of the CPU?speed of the CPU?

A:A: YesYes

Let’s see what you have learned . .Let’s see what you have learned . . . .

Q:Q: What type of processor uses Slot A on a What type of processor uses Slot A on a motherboard?motherboard?

A:A: AMDAMDQ:Q: What is AGP?What is AGP?A:A: Accelerated Graphics Port, Used for Video adaptersAccelerated Graphics Port, Used for Video adaptersQ:Q: What expansion slot runs at 33 MHz?What expansion slot runs at 33 MHz?A:A: PCI – Peripheral Component InterconnectPCI – Peripheral Component InterconnectQ:Q: How many pins are there in a SIMM module?How many pins are there in a SIMM module?A:A: 72 pins72 pinsQ:Q: How many pins are there in a DIMM module?How many pins are there in a DIMM module?A:A: 168 pins168 pins

Q:Q: What type of memory is commonly used as cache?What type of memory is commonly used as cache?

A:A: SRAM – Synchronous Random Access MemorySRAM – Synchronous Random Access Memory

Q:Q: Is a USB device hot swappable?Is a USB device hot swappable?

A:A: YesYes

Q:Q: How many devices can I hook up to a USB device?How many devices can I hook up to a USB device?

A:A: 127127