6666CH
AP
TE
R
THE SYSTEM UNIT
6-2
© 2005 The McGraw-Hill Companies, Inc. All Rights Reserved.
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
6-3
© 2005 The McGraw-Hill Companies, Inc. All Rights Reserved.
System UnitsMicrocomputers
Desktop
Notebook
Tablet PC
Handheld
6-4
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Electronic Data and Instructions
Data and instructions are represented electronically
Computers recognize digital signals
Binary systemBit
Byte
6-5
© 2005 The McGraw-Hill Companies, Inc. All Rights Reserved.
Binary Coding Scheme
Two state systemOff/on electrical states
Characters represented by 0s and 1s
Three types of schemesASCII - American Standard Code for Information Exchange
EBCDIC - Extended Binary Coded Decimal Interchange Code
Unicode
6-6
© 2005 The McGraw-Hill Companies, Inc. All Rights Reserved.
Binary Code
Code Uses
ASCII Microcomputers
EBCDIC Large Computers
Unicode International Languages
6-7
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System Board
Connects all components
Allows communication between devices
Main board or motherboard
Circuit board electronic components
Sockets
Slots
Bus lines
6-8
© 2005 The McGraw-Hill Companies, Inc. All Rights Reserved.
Microprocessor
Central Processing Unit (CPU )
Two basic components Control unit
Arithmetic and logic unit
6-9
© 2005 The McGraw-Hill Companies, Inc. All Rights Reserved.
Microprocessor Chips
Chip capacities are expressed in word sizes
Types of microprocessor chipsCISC chips: Complex instruction chips
Most widely used design
Used by Intel
RISC chips: Reduced instruction set computer chipsUses fewer instructions
Design is simpler and less costly
Used by the PowerPC
6-10
© 2005 The McGraw-Hill Companies, Inc. All Rights Reserved.
Specialty Processors
Graphics coprocessors
Parallel processors
Smart cards
6-11
© 2005 The McGraw-Hill Companies, Inc. All Rights Reserved.
Memory
Holding area for data, instructions, and information
Types of memory chipsRAM – holds programs and data
ROM – fixed start-up instructions
CMOS – flexible start-up instructions
6-12
© 2005 The McGraw-Hill Companies, Inc. All Rights Reserved.
Memory Capacity
UnitUnit CapacityCapacity
Megabyte (MB) 1 billion bytes
Gigabyte (GB) 1 million bytes
Terabyte (TB) 1 trillion bytes
6-13
© 2005 The McGraw-Hill Companies, Inc. All Rights Reserved.
System Clock
Important measurement indicating speed Located on a small chip
Produces electrical beats
Synchronizes operations
Expressed in gigahertz
Faster clock speed, faster computer
What is a gigahertz?
6-14
© 2005 The McGraw-Hill Companies, Inc. All Rights Reserved.
Expansion Slots and Cards
Allow for new devices to be addedOpen architecture
Slots provide for expansion
Expansion cards are also called …Plug-in boards
Controller cards
Adapter cards
Interface cards
6-15
© 2005 The McGraw-Hill Companies, Inc. All Rights Reserved.
Commonly Used Expansion Cards
Video cards
Modem cards
Network interface cards (NIC)
TV tuner cards
PC cards
6-16
© 2005 The McGraw-Hill Companies, Inc. All Rights Reserved.
Bus Lines
Connect parts of the CPU to each other
Data roadway for traveling bitsMeasured as bus width
More lanes, faster traffic
Two basic categoriesSystem buses
Expansion buses
6-17
© 2005 The McGraw-Hill Companies, Inc. All Rights Reserved.
Types of Expansion Buses
Industry Standard Architecture (ISA)
Peripheral Component Interconnect (PCI)
Advanced Graphic Port (AGP)
Universal serial bus (USB)
FireWire buses HPSB – high performance serial bus
Used with digital camcorders & video editing software
6-18
© 2005 The McGraw-Hill Companies, Inc. All Rights Reserved.
Ports
Socket for connecting external devices
Four common portsSerial
Parallel
USB
FireWire
6-19
© 2005 The McGraw-Hill Companies, Inc. All Rights Reserved.
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
AC adapter
Power Supply Unit
6-20
© 2005 The McGraw-Hill Companies, Inc. All Rights Reserved.
A Look to the FutureXybernaut Corporation
Wearable computersCalled POMA Includes…
Windows CEWireless pointing deviceHead-mounted displayMP3 playerAbridged Windows Office programs
6-21
© 2005 The McGraw-Hill Companies, Inc. All Rights Reserved.
Key Terms
AC adapter (164)accelerated graphics port (AGP) (163) adapter card (159)alternating current (AC) (164)analog (151)arithmetic operation (155)Arithmetic logic unit (AL
ASII (152)
binary coding scheme (152)
binary system (151)
bit (151)
bus (162)
bus line (154)
bus width (162)
byte (151)
6-22
© 2005 The McGraw-Hill Companies, Inc. All Rights Reserved.
Key Terms
video card (159)
video capture card (159)
video recorder card (159)
volatile storage (157)
virtual memory (157)
word (155)
workstation (155)
6-23
© 2005 The McGraw-Hill Companies, Inc. All Rights Reserved.
FAQs
What are the four basic types of system units?
What is analog? What is digital?
What is a microprocessor and what does it do?
What is RAM? What is ROM?
I hear a lot about flash memory. What is it?
I need a USB port to install a wireless mouse. What are ports?
What is a network card?
6-24
© 2005 The McGraw-Hill Companies, Inc. All Rights Reserved.
Discussion Questions
Explain how a computer understands instructions.
Define memory and describe three types of memory chips.
Explain the purpose of expansion cards and slots. Give examples of some commonly used expansion cards.
Describe how bus lines work.
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