1. 6 THE SYSTEM UNIT CHAPTER
This chapter identifies and describes the four basic types of system units and system components

2. Competencies Describe the four basic types of system units
Discuss how a computer uses binary codes
Describe the major system unit components
Describe system boards, microprocessors, and memory
Describe the function of the system clock, expansion slots, boards, and bus lines
Discuss ports, cables, and power supply
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3. System Units Microcomputers
Desktop
Notebook
Tablet PC
Handheld
Four basic types of system units (chassis)
Desktop – electronic components and selected secondary storage
Notebook – components, secondary devices, and input devices
PDA – electronic components, secondary storage, input/output devices
Tablet PC – supports the use of a stylus or pen to input commands and data
Convertible table PC – notebook computer with monitor that swivels/folds
Slate tablet PC – similar to notebook but monitor is attached to the system unit and does not have an integrated keyboard
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4. Electronic Data and Instructions
Data and instructions are represented electronically
Computers recognize digital signals
Binary system
Bit
Byte
Our voices recognize analog signals
Continuous signals
Computers only recognize digital 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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5. Binary Coding Scheme Two state system Three types of coding schemes
Off/on electrical states
Characters represented by 0s and 1s
Three types of 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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6. Binary Code Code Uses ASCII Microcomputers EBCDIC Large Computers
Unicode
International Languages
The binary coding scheme shows how characters are represented on computers
When you press on a key on the keyboard, a character is automatically converted into a series of electronic pulses
They are important to computer specialist as well to help track down errors and other types of problems
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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
Chips contain numerous circuits etched on a small wafer of layers of silicon and other materials
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8. Microprocessor Central Processing Unit (CPU ) Two basic components
Control unit
Arithmetic-logic unit
Located on the microprocessor chip and has two components - the control unit and the arithmetic-logic unit
RISC and CISC are two types of microprocessor chips
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
Logical
Microprocessor Chips
Word size
CISC
RISC
Smart Card
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9. Microprocessor Chips Chip capacities are expressed in word sizes
Types of microprocessor chips
CISC chips: Complex instruction set
computer chips
Most widely used design
Used by Intel
RISC chips: Reduced instruction set computer chips
Uses fewer instructions
Design is simpler and less costly
Used by the PowerPC
A word 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
Newer computers
Nanoseconds – microcomputers
Picoseconds – supercomputers
Types of chips
CISC – Intel’s Pentium processors use this chip
RISC – used in powerful workstations
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10. Specialty Processors Graphics coprocessors Parallel processors
Smart cards
Specialty processors are designed to handle special functions
Graphics
Displaying and manipulating 2-D and 3-D graphics images
Parallel
Runs large programs
Approach is called parallel processing
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
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11. Memory Holding area for data, instructions, and information
Types of memory chips
RAM – holds programs and data
ROM – fixed start-up instructions
CMOS – flexible start-up instructions
RAM (Random-access memory)
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)
Nonvolatile; CPU retrieves programs written on the ROM chip
Typical user does not go in and change information on ROM
Also called firmware.
CMOS (complementary metal-oxide semiconductor)
Provides flexibility and expandability for system
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12. Memory Capacity Unit Capacity Megabyte (MB) 1 million bytes
Gigabyte (GB)
1 billion bytes
Terabyte (TB)
1 trillion bytes
Memory is the holding area for data, instructions, and information
Contained on chips connected to the system board
The three commonly used units of measurement are :
Megabyte
Gigabyte
Terabyte
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13. 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
Controls speed of 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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14. 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 card relies on a proprietary add-on, often at more expensive prices
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15. 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)
Modem Card
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 (NICs or Network Interface Cards) - connect system unit to a cable attached to a network
TV turner cards (television boards, video recorder cards, video capture cards) - 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
Inserting a PC card into a notebook
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16. 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
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17. 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
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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18. Types of Expansion Buses
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
Faster than AGP bus
New version is USB 2.0
Bus Pathway
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19. Ports Socket for connecting external devices Four common ports
Serial
Parallel
USB
FireWire
Cables are used to connect exterior devices to the system via the ports
Ports are connecting sockets on the outside of system unit
Four common ports
Serial – data transported one bit at a time; mouse, keyboard, modem, etc.
Parallel – for external devices needing lots of data over short distances, like printers, scanners, external Zip drives
USB (universal serial bus) – gradually replacing serial and parallel ports; can connect multiple devices; faster than parallel
FireWire also known as High Performance Serial Bus (HPSB) – for high-speed printers and video cameras; as fast as USB 2.0
Ports
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20. 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
AC adapter
Power Supply Unit
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21. 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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22. 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.
Have students turn to the end of Chapter 6 in their textbooks to view the same “Open-Ended” questions/statements
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