How Computers Work

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How Computers Work

• Unit 1, Module 3
• PC Hardware Components - Part 2

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Storage Devices

• Temporary (primary storage, or memory)
• Temporarily holds data and instructions while
  processing them
• Faster to access than permanent storage
• Permanent (secondary storage)

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Primary Storage Devices

• Memory, or RAM, located on the motherboard and on
  other circuit boards
• Volatile
• Temp. memory
• Nonvolatile (or ROM) memory
• Memory that holds data permanently even when the
  power is turned off

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Primary Storage Devices

• Common types of boards that hold memory chips
• SIMMs (single inline memory modules)
• DIMMs (dual inline memory modules)
• RIMMs (memory modules manufactured by Rambus,
  Inc.)
• Which one is the most common type of memory used
  today?

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RAM Chips
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Types of RAM ModulesPin Sizes
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Primary Storage Cache Memory

• Cache speeds up memory access, or holding area
  for data or instructions that are accessed
  frequently
• On newer CPUs, cache is stored inside the CPU
  housing on a memory chip that sits very close to
  the CPU microchip
• Older CPUs use COAST (cache on a stick) which is
  memory module on the motherboard or it is stored
  on individual chip

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Secondary Storage Devices

• Permanently hold data, even when PC is turned off
• Hard disks
• Floppy disks
• Zip drives
• CD-ROMs

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Hard Drive

• Contains a platter that rotates at high speed.
• An arm with sensitive read/write head reaches
  across the platters which enables writing new
  data and reading exiting data from the HD.

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Hard Drive

• Uses IDE (Integrated Drive Electronics)
  technology can accommodate up to four EIDE
  devices on one system
• IDE provides two connectors on a motherboard for
  two data cables
• Motherboard can accommodate up to 4 IDE devices
  on one systemHD, Zip Drive, CD-ROM and tape
  Drives

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Motherboard with Two IDE Connectors
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A Typical System
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Floppy Drive

• Sizes 3.5 and the older 5.25 floppy drives
• Requires a controller
• Floppy drive cable allows attach two drivesDrive
  A at the end of the cable and Drive B in the
  middle of the cable
• Electricity to a floppy drive is provided by a
  the power cord from the power supply

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Floppy Drive
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CD-ROM

• Compact Disc Read Only Memory
• Needs a power cord and IDE data cable

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Motherboard Components Used for Communication
Among Devices

• Traces
• Are circuits, or paths, that enable data,
  instructions, and power to move from component to
  component on the board
• Represented by fine lines on both the top and the
  bottom of boards surface
• Traces are also referred as a Bus Lines

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Bus Lines
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Motherboard Components Used for Communication
Among Devices

• The bus
• The ability of the CPU to communicate with the
  rest of the system
• System of pathways used for communication to
  travel between devices.
• The motherboard has more than one bus.

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Motherboard Components Used for Communication
Among Devices

• The System Bus
• Know as the (external bus), (expansion bus),
  (front side bus) or (memory bus)
• The main bus on the motherboard that communicates
  with the CPU, Memory, and the Chip Set, and
  Expansion Slots
• It is know as the external bus because it is
  outside the processor

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Motherboard Components Used for Communication
Among Devices

• The system is bus is a expansion bus because it
  is a bus system that allows the processor to talk
  to another device which are connected to
  expansion slots.
• Types of expansion slots
• PCI (Peripheral Component Interconnect)
• For high-speed input/output devices)
• AGP (Accelerated Graphics Port)
• For a video card
• ISA (Industry Standard Architecture)
• Used by older and/or slower devices)

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System Clock

• Found on a bus to Synchronizes activity on the
  motherboard
• Sends continuous pulses carried on bus over the
  motherboard to chips, expansion slots to ensure
  that all activities are performed in a
  synchronized fashion
• The clock single or pulses are generated by a
  quartz crystal located on motherboard
• Frequency of activity is measured in Megahertz
  (MHz), or 1 million cycles per second

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System Clock

• CPU operates from 166 MHz to two GHz, or two
  thousand MHz (2 billion cycles per second.)
• This means rate of speed that the processor
  executes commands is measured by the clock speed

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Expansion Cards

• Enable the CPU to connect to an external device
  or to a network are mounted in expansion slots on
  the motherboard
• Cards can provide ports as well
• Expansion cards include sound, video, network,
  modem
• Determine the the function of the card by looking
  at the port
• Example Video Card has 15 pins, 3 rows of pins

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The Electrical System

• Power supply
• Converts AC power from the wall outlet into DC
  power that can be used by the computer.
• Newer power supplies provide 3.3, 5 and 12 volts
  of DC.
• Runs a fan directly from electrical output
  voltage to cool inside of computer case

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Instructions and Data Stored on the Motherboard

• ROM (read-only memory) chips store very basic
  instructions and data that are stored on
  motherboard
• ROM chip has software instructions permanently
  etched into the chip is called Firmware
• This type of memory is nonvolatile

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Instructions and Data Stored on the Motherboard

• BIOS (basic input/output system) chips
• ROM Chips hold programs or software the tell CPU
  how to perform many input/output tasks.
• Examples
• ROM BIOS chip on the motherboard contain
  programming to start up the PC and to perform
  other task such as interacting with Floppy Disk
  Drive

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Instructions and Data Stored on the Motherboard

• As new hardware components or BIOS features
  become available the ROM chips need to be
  upgraded or within the past needed to be replaced
• TodayFlash ROM chips allows for ROM chips to be
  reprogrammed or changed without replacing the
  chips

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Instructions and Data Stored on the Motherboard

• CMOS chip
• Also called CMOS RAM
• CMOS contains data about the system
  configuration, current time and date
• When computer turns on, it looks for the CMOS
  chip to find what hardware it should expect to
  find.

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Instructions and Data Stored on the Motherboard

• CMOS chipcontinued
• Powered by a battery on motherboard when power is
  off
• CMOS chip is RAM but the chip retains its data
• If battery dies setup info. is all lost
• Access to a computer can be controlled by
  power-on password in CMOS by accessing the setup
  screen
• Some computers provide a jumper near CMOS chip
  that when set to On causes the computer to
  forget any changes that have been made to default
  settings in CMOS or disable the password

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SetupInstallation Information

• Jumpers two wires that stick up side by side on
  the system board that are used to hold
  configuration information.
• The two pins and the connection together server
  as electrical connection on the motherboard
• If the pins are not connected with a cover, the
  setting is considered OFF
• If the cover is present, the setting is ON.

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Jumpers
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Dip Switches

• Dual Inline Package Switch (DIP)
• Like on a light switch that has on and off
  settings
• Not found on new systems

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Review

• Storage within in a computer consists of primary
  and secondary storage.
• Two types of memory exist within a computer
  Volatile and nonvolatile.
• BIOS provides instructions for your computer in
  order for it to boot.
• Configurations settings are set by using jumpers
  and dip switches.