Transcript Chapter 3: Computer Hardware Components: CPU, Memory, and I/O

Chapter 3:
Computer Hardware Components:
CPU, Memory, and I/O
Berlin Chen 2003
Textbooks: 1. Kurt F. Lauckner and Mildred D. Lintner, "The Computer Continuum,"
Prentice Hall, Second Edition, 2001.
What is the typical
configuration of a computer
sold today?
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Outline
• How did the computer become known as the
stored-program computer?
– Do they all have the same characteristics?
• Memory on chips and memory on magnetic
media, how do they differ?
• What do you look for when comparing memory
devices?
• How is information moved around within the
computer?
• How can you help your computer run better?
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Basic Concepts of Computer
Hardware
Primary Memory
Input
Units
CPU
(Central Processing Unit)
Output
Units
• This model of the typical digital computer is often
called the von Neumann computer
– Programs and data are stored in the same
memory: primary memory
– The computer can only perform one
instruction at a time
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Basic Concepts of Computer
Hardware
• Input/Output (I/O): Refers to the process of
getting information into and out of the computer
– Input: Those parts of the computer receiving
information to programs
– Output: Those parts of the computer that provide
results of computation to the person using the
computer
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Sources of Data
for the Computer
• Two types of data stored within a computer
– Original data or information: Data being
introduced to a computing system for the first time
• Computers can deal directly with printed text, pictures,
sound, and other common types of information
– Previously stored data or information: Data that
has already been processed by a computer and is
being stored for later use
• These are forms of binary data useful only to the
computer
• Examples: Floppy disks, DVD disks, and music CDs
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Input Devices
• Two categories of input hardware:
– Those that deal with original data
– Those that handle previously stored data
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Input Devices
• Input hardware: Those that deal with original
data.
–
–
–
–
–
Keyboard
Mouse
Voice recognition hardware
Scanner
Digital camera
• Digitizing: The process of taking a visual image,
or audio recording and converting it to a binary
form for the computer
– Used as data for programs to display, play or
manipulate the digitized data
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Input Devices
• Connecting Hardware to the computer:
– Hardware needs access through some general
input/output connection.
• Port: The pathway for data to go into and out of the computer
from external devices such as keyboards
– There are many standard ports as well as custom
electronic ports designed for special purposes
– Ports follow standards that define their use
» SCSI, USB: Multiple peripheral devices (chain)
» RS-232, IDE: Individual peripheral devices
• Peripheral device: A piece of hardware like a printer or disk
drive, that is outside the main computer
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Input Devices
• Connecting Hardware to the computer:
(continued)
– Hardware needs software on the computer that can
service the device.
• Device driver: Software addition to the operating system that
will allow the computer to communicate with a particular
device.
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Input Devices
• Common Basic Technologies for Storing Binary
Information:
– Electronic
– Magnetic
– Optical
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Input Devices
• Electronic Circuits
– Most expensive of the three forms for storing binary
information.
– A flip-flop circuit has either one electronic status or
the other. It is said to flip-flop from one to the other.
– Electronic circuits come in two forms:
• Permanent
• Non-permanent
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Input Devices
• Magnetic Technology
– Two parts to most of the magnetic forms of
information storage:
• The medium that stores the magnetic information.
– Example: Floppy disk. Tiny spots on the disk are
magnetized to represent 0s and 1s.
• The device that can “read” that information from the medium.
– The drive spins the disk.
– It has a magnetic sensing arm that moves over the disk.
– Performs nondestructive reading.
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Input Devices
• Optical
– Uses lasers to “read” the binary information from the
medium, usually a disc.
• Millions of tiny holes are “burned” into the surface of the disc.
• The holes are interpreted as 1s. The absence of holes are
interpreted as 0s.
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Input Devices
• Secondary Memory Input Devices
– These input devices are used by a computer to store
information and then to retrieve that information as
needed.
• External to the computer.
• Commonly consists of floppy disks, hard disk drives, or CDROMs.
– Secondary memory uses binary.
• The usual measurement is the byte.
– A byte consists of 8 binary digits (bits). The byte is a
standard unit.
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Input Devices
• The four most important characteristics of
storage devices:
–
–
–
–
Speed and access time
Cost / Removable versus non-removable
Capacity
Type of access
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Input Devices
• Speed (Access time) - How fast information can
be taken from or stored onto the computer
memory device’s medium
– Electronic circuits: Fastest to access
• 40 billionths of a second
– Floppy disks: Very slow in comparison
• Takes up to 1/2 second to reach full speed before access is
even possible
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Input Devices
• Cost
– Megabyte: A Million bytes
– Gigabyte: A billion bytes
– Two parts to a removable secondary storage device
• The cost of the medium (Cheaper if bought in quantity)
• The cost of the drive
Examples:
Cost for drive
Cost for medium
Floppy drive (1.4MB)
Zip 100 (100 MB)
CD-WR (650 MB)
59.00
99.00
360.00 and up
.50
10.00
1.00
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Input Devices
• Capacity - The amount of information that can
be stored on the medium.
Unit
1 bit
1 nibble
1 byte
1 kilobyte
1 megabyte
1 gigabyte
1 terabyte
Description
1 binary digit
4 bits
8 bits
1,024 bytes
1,048,576 bytes
1 million bytes
1,073,741,824 bytes
1 billion bytes
1 trillion bytes
Approximate Size
1 character
1/2 page, double spaced
500,000 pages
5 million pages
5 billion pages
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Input Devices
• Type of Access
• Sequential - Obtained by proceeding through the storage
medium from the beginning until the designated area is
reached (as in magnetic tape)
• Random Access - Direct access (as in floppy and hard
disks)
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Primary Memory
• Primary storage or memory: Is where the data and
program that are currently in operation or being
accessed are stored during use
– Consists of electronic circuits: Extremely fast and
expensive
– Two types
• RAM (non-permanent)
– Programs and data can be stored here for the
computer’s use
– Volatile: All information will be lost once the computer
shuts down
• ROM (permanent)
– Contents do not change
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The Central Processing Unit
• The Central Processing Unit ( CPU)
– Often referred to as the “brain” of the computer
– Responsible for controlling all activities of the
computer system
– The three major components of the CPU are:
1. Arithmetic Unit (Computations performed)
Accumulator (Results of computations kept here)
2. Control Unit (Has two locations where numbers are kept)
Instruction Register (Instruction placed here for analysis)
Program Counter (Which instruction will be performed next?)
3. Instruction Decoding Unit (Decodes the instruction)
– Motherboard: The place where most of the
electronics including the CPU are mounted
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Output Devices
• Output units store and display information
(calculated results and other messages) for us to
see and use.
– Floppy disk drives and Hard disk drives.
– Display monitors: Hi-resolution monitors come in two
types:
• Cathode ray tube (CRT) - Streams of electrons make
phosphors glow on a large vacuum tube
• Liquid crystal display (LCD) - A flat panel display that uses
crystals to let varying amounts of different colored light to
pass through it
– Developed primarily for portable computers
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Output Devices
• Audio Output Devices
– Windows machines need special audio card for audio
output
– Macintosh has audio playback built in
– Audio output is useful for
• Music
– CD player is a computer
– Most personal computers have CD players that can
access both music CDs and CD-ROMs
• Voice synthesis (becoming more human sounding.)
• Multimedia
• Specialized tasks (i.e.: elevator’s floor announcements)
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Output Devices
• Optical Disks: CD-ROM and DVD
– CD-ROM (Compact Disk - Read Only Memory)
• By its definition, CD-ROM is Read Only
• Special CD drives “burn” information into blank CDs
– Burn: A laser is used to “burn” craters into the surface to
represent a binary 1
– Two main types of CDs
» CD-R (Compact Disk - Recordable)
» CD-WR (Compact Disk – Re-Writable)
• It takes longer to write to a CD-R than a hard drive
• Special software is needed to record
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Output Devices
• DVD (Digital Versatile Disk)
– Allows up to 17 gigabytes of storage (from 4.7 GB to
17 GB).
– Compatible with older CD-ROM technology.
– The four versions of the DVD:
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Output Devices
• Storage Requirements: How much storage
capacity is needed for…
–
–
–
–
–
One keystroke on a keyboard.
One page single-spaced document.
Nineteen pages formatted text.
One second of high-fidelity sound.
Complete word processing program.
1 byte (8 bits)
4.0 K
75 K
95-110 K
8.4 MG
• Storage Capacity: How much data can be stored
on…
–
–
–
–
One inch of 1/2 in. wide magnetic tape.
One 3 1/2” floppy disk, high density.
One Compact Disk.
One DVD.
4K
1.4 MG
650 MG
up to 17 GB
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Moving Information
Within the Computer
• How do binary numerals move into, out of, and
within the computer?
– Information is moved about in bytes, or multiple bytes
called words
• Words are the fundamental units of information
• The number of bits per word may vary per computer
• A word length for most large IBM computers is 32 bits
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Moving Information
Within the Computer
• Bits that compose a word
are passed in parallel
from place to place.
– Ribbon cables:
• Consist of several wires,
molded together
• One wire for each bit of
the word or byte
• Additional wires
coordinate the activity of
moving information
• Each wire sends
information in the form of
a voltage pulse
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Moving Information
Within the Computer
• Example of
sending the word
WOW over the
ribbon cable
– Voltage pulses
corresponding
to the ASCII
codes would
pass through
the cable.
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Packaging the Computer
• The many physical forms of
the general purpose
computer:
– All follow general
organization:
•
•
•
•
Primary memory
Input units
Output units
Central Processing Unit
– Grouped according to
speed, cost, size, and
complexity.
Fast Expensive Complex Large
Super Computers
Mainframe Computers
Minicomputers
Microcomputer
Palmtop Computer
Calculator
Slow Cheap Simple Small
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Supercomputers
• Supercomputers are the most powerful computers. They
are used for handling large and highly complex problems
that requires extreme calculating power
– Can perform more than 1 trillion calculation per second
– E.g. Cray T90 system houses thousands of processors
• Because of their size and expense, supercomputers are
relatively rare.
– Help analyze and forecast weather, nuclear science, DNA
structure (80,000~100,000 human genes), etc
– Housed in a protected room with special cooling systems, power
protection, and other security features
• Supercomputers are used by universities, government
agencies, and large businesses.
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Supercomputers
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Mainframe Computers
• Mainframe computers can support hundreds or
thousands of users, handling massive amounts of input,
output, and storage
– The largest type of computer in common use
• Mainframe computers are used in large organizations
where many users need access to shared data and
programs
– Insurance companies, banks, airlines, government agencies
• Mainframes are also used as e-commerce servers,
handling transactions over the Internet
– Are being used more and more as specialized servers on the
Word Wide Web (WWW), enabling companies to offer secure
transactions with customers over the Internet
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Mainframe Computers
• In a traditional mainframe environment, each user works
at a computer terminal
– A terminal is a monitor and a keyboard wired to the mainframe
• Many enterprises are now connecting personal
computers and computer networks to their mainframe
systems
– PCs have local storage and processing capabilities
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Minicomputers
• Minicomputers are smaller than mainframes but larger
than microcomputers
– Also called “midrange computers
• Minicomputers usually have multiple terminals
– Though some are designed for a single user
• Minicomputers may be used as network servers and
Internet servers
– Handle data-sharing needs of other computers on the network
– Dozens or hundreds of personal computers connected to a
network with a minicomputer as a server
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Workstations
• Workstations are powerful single-user computers
– Somewhere between multi-user midrange computers and
personal computers
– Popular among scientists, engineers, graphic artists, etc.
– Featured advanced processors, more RAM and storage
capability than PCs
– Until few years ago, the term workstation implied certain different
in chip design and operating system, making it distinct from
PCs
• Workstations are used for tasks that require a great deal
of number-crunching power, such as product design and
computer animation
– Have large, high-resolution monitors and accelerated graphicshandling capabilities
• Workstations are often used as network and Internet
servers
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Workstations
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Microcomputers
• Microcomputers are more commonly known as personal
computers (PC). The term "PC" is applied to IBM-PCs or
compatible computers
– In 1981, IBM called its first microcomputer the IBM-PC
– The Apple Macintosh is another family of microcomputers
• Full-size desktop computers are the most common type
of PC
• Notebook (laptop) computers are used by people who
need the power of a desktop system, but also portability.
• Handheld PCs (such as PDAs) lack the power of a
desktop or notebook PC, but offer features for users who
need limited functions and small size
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Microcomputers
iMac, Apple Macintosh Computer
Horizontally-oriented PC
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Microcomputers
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Software Tools for Maintaining Your
Computer Hardware
• Utility Programs exist that can help diagnose and solve
computer hardware problems
– Four major problem areas where utility programs are
helpful
• Finding and fixing problems
– Testing Input/Output peripherals
– Testing RAM, motherboard, video cards
– Recovering deleted files or fixing damaged disks
• Improving computer performance
– De-fragmenting a disk (Packs all files closer together)
• Preventative maintenance
• Troubleshooting
– Locates incompatible programs
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