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.

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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

• 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

CPU(Central Processing Unit)

InputUnits

OutputUnits

Primary Memory

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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 Datafor 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 CD-

ROMs.

– 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) 59.00 .50

Zip 100 (100 MB) 99.00 10.00

CD-WR (650 MB) 360.00 and up 1.00

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Input Devices

• Capacity - The amount of information that can be stored on the medium.

Unit Description Approximate Size

1 bit 1 binary digit1 nibble 4 bits1 byte 8 bits 1 character1 kilobyte 1,024 bytes 1/2 page, double spaced1 megabyte 1,048,576 bytes 500,000 pages

1 million bytes1 gigabyte 1,073,741,824 bytes 5 million pages

1 billion bytes1 terabyte 1 trillion bytes 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. 1 byte (8 bits)– One page single-spaced document. 4.0 K– Nineteen pages formatted text. 75 K– One second of high-fidelity sound. 95-110 K– Complete word processing program. 8.4 MG

• Storage Capacity: How much data can be stored on…– One inch of 1/2 in. wide magnetic tape. 4 K– One 3 1/2” floppy disk, high density. 1.4 MG– One Compact Disk. 650 MG– One DVD. up to 17 GB

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Moving InformationWithin 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 InformationWithin 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 InformationWithin 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.

Super Computers

Mainframe Computers

Minicomputers

Microcomputer

Palmtop Computer

Calculator

Fast Expensive Complex Large

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 graphics-

handling 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

Horizontally-oriented PCiMac, Apple Macintosh Computer

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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