THE SYSTEM UNIT

SYSTEM UNIT

- also known as system chassis

- contains electronic components that make up a computer system

Basis categories of system units

ELECTRONIC DATA AND INSTRUCTIONS

•          Data and instructions are represented electronically
•         Two-state or binary system is used to represent data and instructions

  ·    BS consists of only two digits- 0 and 1

  · Bit = short for binary digit

  ·   Bytes = bits are combined into group of eight

-        Three types of binary coding schemes

·      ASCII - American Standard Code for Information Interchange

·      EBCDIC - Extended Binary Coded Decimal Interchange Code

·      Unicode– handles languages with large numbers of characters

SYSTEM BOARD

   -        Connects all components

   -        Allows communication between devices

   -        Main board or motherboard

   -        Circuit boardelectronic components

·      Sockets

·      Slots

·      Bus lines

 

MICROPROCESSOR

   -        Central Processing Unit (CPU)

   -        Two Basic Components

    ·      Control unit

    ·      Arithmetic-logic unit (ALU)

       Microprocessor Chips

   -        Chip capacities are expressed in word sizes

   -        Two Recent Significant Developments

·      64-bit processors

~ Have become standard for most of today’s desktop and laptop computers

·      Multi-Core Chips

~ Can provide two separate and independent CPUs

~ Parallel processing

Specialty Processors

   -        Coprocessors

·      Designed to improve specific computing operations

·      Graphics coprocessors

   -        Smart cards

·      Credit card sized with an embedded chip

·      Used by many universities

   -        Specialty processors in cars

·      As many as 70

·      Used to control features

   -        RFID tags

·      Information chips

·      Used for tracking purposes

MEMORY

   -        Holding area for data, instructions, and information

  -   Memory is contained on chips connected to the system board

RAM

   -        Called VOLATILE STORAGE/TEMPORARY

·      Their content will lose if power is disrupted

   -        Cache memory

·      High-speed holding area for frequently useddata and information

   -        DIMM (dual in-line memory module)

·      Used to expand memory

   -        Virtual memory

·      Divides program into parts that are read inRAM as needed

 

ROM

  -        Read-only memory (ROM) chips are not volatile and cannot be changed by the user

  -       CPU can read, or retrieve data and programs but the computer cannot write

   -        Contain special instructions

·      Needed to start a computer

·      Give keyboard keys their special capabilities

·      Put characters on screen

Flash Memory

   -    Flash memory offers a combination of the features of RAM and ROM. 

   -      Flash memory is used for a wide of range of applications.

   -       If changes are made to the computer system, these changes are reflected in flash memory.

EXPANSION SLOTS AND CARDS

   -        Insert expansion cards into slot

   -        Ports on the card allow cables connect to devices outside the SU

   -        Types of EC:

  ·      Graphics cards

  ·      Sound cards

  ·      Modem cards

  ·      Network interface cards (NIC)

  ·      PC cards and Express cards

  ·      TV tuner- Allows you to view your favourite TV shows

BUS LINES

   -        Connect parts of the CPU to each other

   -        Data roadway for traveling bits

·      Measured as bus width

·      More lanes, faster traffic

   -        Two basic categories

·      System buses

·      Expansion buses

Expansion Buses

  -  Connects the CPU to other components on the system board, including expansion slots

    -        Principal types

·      PCI Express (PCIe)

·      Peripheral Component Interconnect (PCI)

·      Universal serial bus (USB)

·      FireWire buses

·      Serial Advanced Technology Attachment (SATA)

PORTS

   -        Socket for connecting external devices

   -        Ports can connect directly to the system board or they can connect to cards that are inserted into slots on the system board

Standard Ports

   -        Four common ports

·      VGA

·      USB ports

·      FireWire ports

·      Ethernet ports

 

Legacy Ports

   -        Serial ports

   -        Parallel ports

   -        Keyboard and mouse ports

   -        Game ports

   -        Infrared data association (IrDA)

Specialized Ports

   -        Three specialized ports

·      Musical Instrument digital interface (MIDI)

·      Sony/Philips Digital Interconnect Format (S/PDIF)

·      High Definition Multimedia Interface (HDMI)

Cables

   -    Used to connect exterior devices to the system unit via the ports

  -      One end of the cable is attached to the device and the other end has a connector that is attached to a matching connector on the port

 

POWER SUPPLY

   -        Computers require direct current (DC)

   -      DC power provided by converting alternating current (AC) from wall outlets or batteries

   -        Desktop computers use power supply units

   -        Notebooks and handhelds use AC adapters

Careers in IT

  -  Computer technicians repair and install computer components and systems

     -          Employers look for

·      Certification in computer repair

·      Good communication skills

     -        Continued education is required

     -        Computer technicians can expect to earn an hourly wage of $13.50 to $22.50

•         References from

        1. Computing Essentials Complete 2010 by Timothy J.O'Leary and Linda I.O'Leary from McGRAW Hill

2.http://en.wikipedia.org/wiki/Computer_case

3.http://www.techterms.com/definition/system_unit