1. Chapter 6
The System Unit

2. Competencies (1 of 2) Describe the four basic types of system units
Discuss how a computer uses binary codes to represent data in electronic form
Describe each of the major system unit components
Discuss microprocessors, including specialty processors
Describe the different types of memory
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3. Competencies (2 of 2) Discuss expansion slots and boards
Describe the five principal types of expansion buses
Discuss the four standard ports
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4. System Unit Desktop System Units Notebook System Units
Tablet PC System Units
Handheld Computer
System Units
Four basic types of system units (chassis) (Key Term)
Desktop – electronic components and selected secondary storage
Horizontal models
Vertical models or tower models (Key Term)
Notebook – components, secondary devices, and input devices
Tablet PC (Key Term) – supports the use of a stylus or pen to input commands and data
Convertible tablet PC (Key Term) – notebook computer with monitor that swivels/folds
Slate tablet PC (Key Term) – similar to notebook but monitor is attached to the system unit and does not have an integrated keyboard
Hand-held computer systems
Personal digital assistant (Key Term) (PDA) – electronic components, secondary storage, input/output devices
Palm computers (Key Term) - contain an entire computer system
System unit is also referred to as the system cabinet (Key Term)
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5. Electronic Data and Instructions
Data and instructions are represented electronically
Two-state system or Binary System
Off/on electrical states
Characters represented by 0s and 1s
Bits
Bytes
Our voices recognize analog (Key Term) signals
Continuous signals
Computers only recognize digital (Key Term) signals
Electrical
On/off state
The binary system consists of two digits – 0 and 1
Each 0 or 1 is called a bit – short for binary digit
Bits are combined into groups of eight bits called bytes
Smallest character = bit; eight bits = 1 byte or one character
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6. Binary Coding Schemes Three types of binary coding schemes
ASCII - American Standard Code for Information Exchange
EBCDIC - Extended Binary Coded Decimal Interchange Code
Unicode – handles languages with large numbers of characters
Knowing this information helps understand what takes place when data entered into computer – why it takes “so long” for the data to get transformed
Three basic schemes of coding
ASCII – primarily desktop
EBCDIC – primarily mainframe and super
Unicode – to handle languages with large numbers of characters
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7. System Board Connects all components
Allows communication between devices
Main board or motherboard
Circuit board electronic components
Sockets
Slots
Bus lines
Connects all system components and allows input and output devices to communicate with system unit
Other names: main board; motherboard
Located in the system unit, consists of a large flat circuit board with sockets and chips (Key Term)
Chips contain numerous circuits etched on a small wafer of layers of silicon and other materials
Chips are mounted on carrier packages (Key Term)
Chips are also referred to as a silicon chip (Key Term), semiconductor (Key Term), or integrated circuit (Key Term)
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8. Microprocessor Central Processing Unit (CPU) Two Basic Components
Control unit
Arithmetic-logic unit (ALU)
Located on the microprocessor chip and has two components - the control unit and the arithmetic-logic unit
Control Unit
Program instructions
Directs flow between memory and Arithmetic-Logic Unit
Directs flow between CPU and I/O devices
Arithmetic-Logic Unit - ALU
Two types of operations
Arithmetic operation (Key Term)
Logical operation (Key Term)
Microprocessor Chips
Word size
CISC
RISC
Smart Card (Key Term)
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9. Microprocessor Chips Chip capacities are expressed in word sizes
Two Recent Significant Developments
64-bit processors
Becoming more commonplace
Windows XP Professional X64 Edition
Dual-Core Chips
Can provide two separate and independent CPUs
Parallel processing
A word (Key Term) is the number of bits that can be accessed at one time by the CPU
Older computers process data and instructions in millionths of a second – microseconds (Key Term)
Newer computers
Nanoseconds (Key Term) – microcomputers
Picoseconds (Key Term) – supercomputers
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10. Specialty Processors Coprocessors Smart cards RFID tags
Designed to improve specific computing operations
Graphics coprocessors
Smart cards
Credit card sized with an embedded chip
Used by many universities
RFID tags
Information chips
Used for tracking purposes
Specialty processors are designed to handle special functions
Graphics
Displaying and manipulating 2-D and 3-D graphics images
Smart cards (and readers)
Plastic cards that have an embedded chip
Can store 80 times the information stored on the magnetic strip of a regular credit card
RFID tags
Used by luxury car manufacturers for fuel efficiency, tracking, and satellite entertainment
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11. Memory Holding area for data, instructions, and information
Memory is contained on chips connected to the system board
Types of memory chips
RAM
ROM
CMOS
RAM (Random-access memory) (Key Term)
Frequently accessed
Acts as high-speed, temporary holding area
Faster processing results
Temporarily holds data and programs being processed by the CPU
Volatile - when power shuts off, contents of RAM are emptied
Exception - flash RAM can retain data when power disrupted, used in high end portable computers
Cache (pronounced: “cash”)
Area in RAM set aside to store information frequently accessed
Acts as a high-speed, temporary holding area for parts of programs and data
Results in faster processing results for the user
ROM (Read-only memory) (Key Term)
Nonvolatile; CPU retrieves programs written on the ROM chip
Typical user does not go in and change information on ROM
Also called firmware (Key Term).
CMOS (complementary metal-oxide semiconductor) (Key Term)
Provides flexibility and expandability for system
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12. RAM Random Access Memory (RAM) chips hold the program and data
Cache memory or RAM cache
Flash RAM or flash memory
Other types of RAM
DRAM
SDRAM
DDR
Direct RDRAM
Cache memory – improves processing by acting as a temporary high-speed holding area between the memory and CPU
Flash memory – can retain data even if the power is disrupted
Most expensive type of RAM
Used for digital telephones, digital video cameras, and portable computers
Virtual Memory (Key Term) – large programs are divided into parts and the parts are stored on a secondary device, usually a hard disk. Each part is then read into RAM only when needed
RAM is also referred to as temporary or volatile storage (Key Term)
It is a good idea to save your work in progress to a second a secondary storage device. which is permanent or nonvolatile storage (Key Term)
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13. 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
ROMs are also called firmware
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14. CMOS
Complementary metal-oxides semiconductor (CMOS) chips provide flexibility for a computer system
Contains essential information every time the computer is turned on
Date and time
Amount of RAM
Type of keyboard
Content can be changed to reflect changes in the computer system
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15. System Clock Important measurement indicating speed
Located on a small chip
Produces electrical beats
Synchronizes operations
Expressed in gigahertz (GHz)
(billions of beats per second)
Faster clock speed, faster computer
System clock (Key Term) controls the speed of the system
Synchronizes operations inside the computer
Expressed in gigahertz, or millions of cycles per second
Faster the clock speed, the faster the computer
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16. Expansion Slots and Cards
Allow for new devices to be added
Open architecture
Slots provide for expansion
Expansion cards are also called …
Plug-in boards
Controller cards
Adapter cards
Interface cards
Expansion slots provide an open architecture
Expansion cards provide network connections, PC/TV combinations, and more
This open architecture allows users to expand and update their systems
Devices to meet these needs, expansion cards, are inserted into the expansion slots
A closed architecture (Key Term) card relies on a proprietary add-on, often at more expensive prices
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17. Commonly Used Expansion Cards
Video cards (graphics cards)
Sound cards
Modem cards (internal modems)
Network interface cards (NIC)
TV tuner cards
PC cards (PCMCIA cards)
Video cards – known as graphics cards; connect the system board to the monitor; convert internal electronic signals to video signals
Sound cards – convert electronic signals to audio signals and accept audio input from microphones
Modem cards – allow distant computers to communicate with each other by converting computer electronic signals to travel over phone lines
Network adapter cards (Key Term) (NICs or Network Interface Cards) - connect system unit to a cable (Key Term) attached to a network
TV turner cards (Key Term) (television boards (Key Term), video recorder cards (Key Term), video capture cards (Key Term)) - PC/TV combination cards led to high audio quality systems called home PCs
TV tuner converts video signal for viewing on computer monitor
PC cards - credit card-sized expansion cards for portable computers, also known as PCMCIA (Personal Computer Memory Card International Association) cards (Key Term)
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18. Plug and Play
Set of hardware and software standards developed by Intel, Microsoft, and others
Creating devices that are able to configure themselves when installed
Not all computer systems and expansion cards have plug and play (Key Term) capabilities
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19. 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
Bus lines provide data pathways that connect various system components
A bus line is also called a bus (Key Term)
It is a pathway for bits representing data and instructions
Every computer has two basic categories of buses
System – connects the CPU to memory on the system board
Expansion – connects the CPU to slots on the system board
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20. Expansion Buses
Connects the CPU to other components on the system board, including expansion slots
Principal types
Industry Standard Architecture (ISA)
Peripheral Component Interconnect (PCI)
Accelerated Graphics Port (AGP)
Universal serial bus (USB)
FireWire buses
Remember that architecture determines whether or not new devices can be easily added
Industry Standard Architecture (ISA) – developed for IBM PC 8 bits then expanded to 16 bits, although slow, still widely used
Peripheral Component Interconnect (PCI) – originally for video demands of GUI (graphical user interfaces); widely used to connect CPU, memory, and expansion boards; either 32 or 64 bit, more than twenty times faster than an ISA
Accelerated Graphics Port (AGP), over twice as fast as PCI bus; dedicated to acceleration of graphics and 3-D animations; closer to CPU and faster access for video cards
Universal serial bus (USB) – gradually replacing serial and parallel ports (Key Term)
Faster than AGP bus
New version is USB 2.0
FireWire buses – High-performance serial bus (HPSB) (Key Term) – operate much like the USB buses and perform at speeds comparable to USB 2.0
Used with digital camcorders
Used with video editing software
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21. TV Tuner Cards And Video Clips
Allows you to view your favorite TV shows while running other applications such as Excel
Video can be captured to a file, added to a Web page, attached to an , or added to a class presentation
Relatively inexpensive and
easy to install
Factors that could limit the performance
Speed of the processor
Amount of memory
Secondary storage capacity
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22. 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
Two Types
Standard Ports
Specialized Ports
Ports are connecting sockets on the outside of a system unit
Ports are often standard features of computer systems and others are more specialized
Ports
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23. Standard Ports Four common ports Serial ports Parallel ports USB ports
FireWire ports
Four common ports
Serial ports – data transported one bit at a time; mouse, keyboard, modem, etc.
Parallel ports – for external devices needing lots of data over short distances, like printers, scanners, external Zip drives
USB ports (universal serial bus) – gradually replacing serial and parallel ports; can connect multiple devices; faster than parallel
FireWire ports also known as high performance serial bus (HPSB) ports (Key Term) – for high-speed printers and video cameras; as fast as USB 2.0
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24. Specialized Ports Three specialized ports
Musical Instrument digital interface (MIDI)
Smaller computer system interface (SCSI)
Infrared data association (IrDA)
MIDI – special type of serial port for connecting musical instruments
SCSI – special type of high-speed parallel port for connecting a series of input and/or output SCSI devices to a single SCSI controller card
IrDA – also known as fast infrared ports (FIR). They provide a wireless mechanism for transferring data between devices
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25. 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
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26. 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
Cables are used to connect exterior devices to the system unit via the ports
Direct current (DC) powers computers
Desktop computers have a power supply unit located within the system unit
Notebook computers use AC adapters that are located outside the system unit
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27. 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 $25K - $50K annually
Opportunities for advancement typically come in the form of work on more advanced computer systems
Some computer technicians move into customer service positions or go into sales
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28. A Look to the Future Xybernaut Corporation
Wearable computers
Called POMA
Includes…
Windows CE
Wireless pointing device
Head-mounted display
MP3 player
Abridged Windows Office programs
Xybernaut Corp is currently marketing a personal wearable computer called POMA
The device is described as a personal multimedia appliance
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29. Discussion Questions Describe the four basic types of system units.
Describe the two basic components of the CPU.
What are the differences and similarities between the three types of memory?
Identify five expansion cards and describe the function of each.
Identify and describe four standard ports and three specialized ports.
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