Computers and Networking Systems

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Computers and Networking Systems

• Class 2.1

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Chapter 1

• How Computers Work

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How a CPU Works and Communicates with Other
Devices

• Responsible for most processing
• Depends on chip set, system clock, and buses to
  move data to and from I/O devices, memory, and
  secondary storage
• Only two states on and off

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Components of a CPU

• Input/output (I/O) unit
• Manages data and instructions entering and
  leaving the CPU
• One or more arithmetic logic units (ALU)
• Does all comparisons and calculations
• Control unit
• Manages all activities inside CPU itself

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Components of a CPU
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How the CPU Works

• Registers hold data and instructions while it
  processes them
• Memory cache holds data and instructions just
  before they are processed
• Internal bus runs at different speed than
  external bus

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Interrupt Request (IRQ) Lines
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I/O Control Lines
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Understanding Binary

• With computers, everything is binary every
  process is a series of zeros and ones
• Decimal and hexadecimal notations are two
  shorthand ways of displaying binary numbers

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Understanding Binary

• Hexadecimal notation (hex)
• Shorthand way to display long binary numbers
  easier for humans to understand
• Built on multiples of sixteen
• ASCII (American Standard Code for Information
  Interchange) standard
• Has assigned an 8-bit code for letters, symbols,
  and other characters

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Computer Terminology
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Chapter 2

• How Hardware and Software Work Together

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Hardware and Software Interaction An Overview

• Software
• Intelligence of the computer
• Determines what hardware is present
• Decides how hardware is configured and used
• Uses hardware to perform tasks
• Consists of programs that instruct computers to
  perform specific tasks

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Operating System (OS)

• Software that controls a computer
• Manages hardware
• Runs applications
• Provides user interface
• Stores, retrieves, and manipulates files
• Communicates with hardware using system
  resources uses BIOS or device drivers for
  interface to system resources

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Categories of PC Software

• BIOS (basic input/output system) and device
  drivers
• Operating system (OS)
• Application software

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System Resources

• Tools used by hardware or software to communicate
  with the other
• Memory addresses
• I/O addresses
• Interrupt request numbers (IRQs)
• Direct memory access (DMA) channels
• All four types depend on certain lines on a bus
  on the motherboard

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System Resources
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Interrupt Request Number (IRQ)

• Line on a bus that a device uses to alert the CPU
  that it needs servicing
• Interruptions to CPU are called hardware
  interrupts
• Polling is an alternative to an interrupt

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Common Uses for Some IRQs
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IRQs

• Preconfigured assignments make it easier to
  configure devices and avoid conflicts with other
  devices
• COM1 and COM2 (for serial devices such as modems)
• LPT1 and LPT2 (for parallel devices such as
  printers)

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IRQs
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Memory Addresses

• Hexadecimal numbers, often written in
  segment/offset form, assigned to RAM and ROM so
  that the CPU can access both

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How Memory AddressesAre Assigned

• CPU has fixed number of memory addresses,
  determined by CPU and bus it is using
• They can be assigned to any type of physical
  memory in the system that needs to be addressed
  by the CPU
• Once addresses have been assigned (usually during
  boot process), CPU sees physical memory as a
  single list that can be accessed using memory
  addresses

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How Memory AddressesAre Assigned
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Assignments for I/O Addresses
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DMA Channels

• Provide shortcuts for a device to send data
  directly to memory bypasses CPU
• A chip on the motherboard contains DMA logic and
  manages the process
• Each channel requires two lines to manage it
• One for DMA controller to request clearance from
  CPU
• One used by CPU to acknowledge that DMA
  controller is free to send data over data lines
  without interference from CPU

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Booting up Your Computer

• Refers to the computer bringing itself up to an
  operable state without user intervention
• Hard boot (cold boot)
• Involves initially turning on power with on/off
  switch
• More stressful than soft boot because of initial
  power surge through equipment
• Soft boot (warm boot)
• Uses OS to reboot
• Faster than hard boot

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Plug and Play (PnP) Standard

• Makes installing hardware devices less
  complicated
• Rather than having to reset DIP switches and
  jumpers, OS and/or startup BIOS automatically
  configures hardware devices to reduce or
  eliminate conflicting requests for system
  resources
• Applies to OS, BIOS on the motherboard, and BIOS
  on devices

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Functions PerformedDuring the Boot

• Startup BIOS tests essential hardware components
  (power-on self test or POST)
• Setup information is used to configure both
  hardware and software
• Hardware components are assigned system resources
  they will later use for communication

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Functions PerformedDuring the Boot

• Startup BIOS finds the OS, which is loaded,
  configured, and executed
• Hardware devices are matched up with the BIOS and
  device drivers that control them
• Some application software may be loaded and
  executed

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Boot Step 1
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How BIOS Finds/Loads the OS
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Boot Step 3
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Chapter 3

• Electricity and Power Supplies

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The Properties of Electricity
continued
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The Properties of Electricity
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Relationships Among Voltage, Current, and
Resistance

• Voltage and current have a direct relationship
• When voltage increases, current increases
• Resistance has an inverse relationship with
  voltage and current
• As resistance increases, either current or
  voltage decreases
• As resistance decreases, either current or
  voltage increases (Ohms Law)

continued
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Relationships Among Voltage, Current, and
Resistance

• An electrical circuit is created by a combination
  of voltage, current, and resistance
• One volt drives a current of one amp through a
  resistance of one ohm

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AC (Alternating Current)

• Cycles or oscillates back and forth
• Most economical way to transmit electricity to
  homes and workplaces

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DC (Direct Current)

• Travels in only one direction
• Required by most electronic devices, including a
  computer (power supply acts as both a rectifier
  and a transformer)
• Rectifer
• Converts alternating current to direct current
• Transformer
• Changes the ratio of current to voltage

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Computer Power Supply
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Materials Used to Make Electrical Components

• Conductors
• Insulators
• Semiconductors

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Transistor

• Electronic device that can serve as a gate or
  switch for an electrical signal
• Can amplify flow of electricity
• Made of three layers of semiconductor material
• Basic building block of an integrated circuit
  (IC) that is used to build a microchip

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Capacitor

• Can hold an electrical charge
• Smoothes out uneven flow of electricity through a
  circuit
• Maintains a charge long after current is no
  longer present

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Diodes and Resistors

• Diode
• Semiconductor device that allows electricity to
  flow in only one direction
• Resistor
• Electronic device that limits amount of current
  that can flow through it

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Protecting Your Computer System General
Precautions

• Dont touch chips on motherboard or expansion
  cards
• Dont touch a chip with a magnetized screwdriver
• Dont use a graphite pencil to change DIP switch
  settings
• Turn off a computer before moving it
• Keep disks away from magnetic fields, heat, and
  extreme cold

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Protecting Against Electricity

• Turn off power and unplug computer
• Use a ground bracelet
• Never touch inside of a computer while it is
  turned on
• Never remove cover or put your hands inside
  monitor or power supply

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Static Electricity

• Electrostatic discharge (ESD)
• Electrical charge at rest
• Brief flow of electricity caused by contact
  between two objects that had a difference in
  voltage potential
• Can cause catastrophic or upset failure
• How to protect against ESD
• Ground bracelet or static strap
• Ground mats
• Static shielding bags

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EMI (Electromagnetic Interference)

• Caused by magnetic field produced as a side
  effect when electricity flows
• How to protect against EMI
• Cover expansion slots
• Dont place system close to or on same circuit as
  high-powered electrical equipment
• Use line conditioners

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Surge Protectionand Battery Backup

• Devices that control electricity to a computer
• Surge suppressors
• Power conditioners
• Uninterruptible power supplies (UPSs)
• All should have UL (Underwriters Laboratory) logo

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Surge Suppressors

• Protect equipment against damaging spikes in
  electrical voltage
• Also called a surge protector
• Can come as power strips, wall-mounted units that
  plug into AC outlets, or consoles some provide
  RJ-11 telephone jack to protect modems and fax
  machines from spikes
• Data line protector (for phone line)

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Power Conditionersand UPSs

• Condition power passing through them
• Provide some protection against spikes and raise
  voltage when it drops during brownouts
• Measured by the load they support in watts,
  volt-amperes (VA), or kilovolt-amperes (kVA)

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Uninterruptible Power Supply

• Benefits
• Conditions line for brownouts and spikes
• Provides backup power during a blackout
• Protects against very high potentially damaging
  spikes
• Types
• Standby device
• Switches from one circuit to another when a
  blackout begins
• Inline device
• Provides continuous power
• Line-interactive device

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AT Form Factor

• Used on older motherboards
• Uses full-size AT cases used by original IBM AT
  personal computer
• Cannot be used with smaller AT cases or with
  newer ATX cases
• Difficult to install, service, and upgrade
• No longer produced by most manufacturers

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AT Motherboard
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ATX

• Superseded earlier AT and Baby AT form factors
• Open, nonproprietary industry specification
  developed by Intel in 1995
• Easier to add and remove components
• Greater support for I/O devices and processor
  technology
• Lower costs
• Better positioning of components on motherboard

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ATX

• Possible to reduce cable lengths, which can help
  reduce potential for EMI and corrupted data
• Power supply and motherboard use single power
  connector (P1 connector)
• Power supply fan blows air into case cools
  processor directly
• Soft switch feature
• Other types of ATX boards (Mini-ATX, MicroATX,
  FlexATX )

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ATX Motherboard
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A Desktop Case
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Minitower
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A Digital Multimeter
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Using a Multimeter

• Before you begin, tell the multimeter
• What you want it to measure (voltage, current, or
  resistance)
• Whether current is AC or DC
• Expected range of values
• How to measure voltage
• How to measure current
• How to measure continuity

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Measuring Voltageof a Power Supply
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Measuring Voltage Output to an AT Motherboard
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Measuring Voltage Output to an ATX Motherboard
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Upgrading Your Power Supply

• Easiest way to fix a power supply you suspect is
  faulty is to replace it

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Introduction to Troubleshooting

• Isolate the problem
• Problems that prevent PC from booting
• Problems that occur after a successful boot

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Questions to Ask

• When did the problem start?
• Were there any error messages or unusual displays
  on the screen?
• What programs or software were you using?
• Did you move the system recently?
• Has there been a recent thunderstorm or
  electrical problem?

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Questions to Ask

• Have you made hardware, software, or
  configuration changes?
• Has someone else been using your computer
  recently?
• Can you show me how to reproduce the problem?
• Does the PC boot properly?

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PC Problem Solving
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Guidelines for Troubleshooting the Power System

• Are there any burnt parts or odors?
• Is everything connected and turned on? Loose
  cable connections? Computer plugged in?
• Are all switches turned oncomputer, monitor,
  surge protector, UPS, separate circuit breaker?
  Is wall outlet good?
• If fan is not running, turn off computer, open
  case, and check connections to power supply. Are
  they secure? Are all cards securely seated?

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Troubleshooting the Power System

• Check for correct wire connections to the
  motherboard
• Remove all nonessential expansion cards one at a
  time
• Vacuum entire unit

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Potential Outcomes of a Faulty Power Supply

• Memory errors
• Data errors
• System hangs
• System reboots
• Damage to a motherboard or other component

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Troubleshooting the Power Supply Itself

• Remove dust from power supply and vents
• Check that power supply fan and fan over CPU are
  working
• Remove other devices that use same circuit
• Upgrade power supply
• Measure voltage output or exchange power supply
  for one you know is good
• Install electrical conditioner to monitor and
  condition voltage

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Troubleshooting the Power Supply Fan

• Replace fan
• Replace entire power supply

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Power Problems with the Motherboard

• Is it grounded to the chassis?
• Check for missing standoffs
• Check for shorts
• Never replace a damaged motherboard without
  testing the power supply