Systems Architecture, Fifth Edition

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Chapter Goals

• Discuss the development of automated computing
• Describe the general capabilities of a computer
• Describe computer system components and their
  functions
• List computer system classes and their
  distinguishing characteristics
• Define the role and function of application and
  system software

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Chapter Goals (continued)

• Describe the economic role of system and
  application development software
• Describe the components and functions of computer
  networks

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Systems Architecture

• Describes structure, interaction, and technology
  of computer system components
• Capabilities of a computer
• Accept numeric inputs
• Perform computational functions
• Communicate results

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Automated Computation

• Mechanical
• Early computers with limited capabilities
• Electronic
• Fast, accurate reliable
• Optical
• Fast, accurate reliable

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Mechanical Implementation

• Mechanical representation of a mathematical
  calculation
• Difference engine - Charles Babbage, 1821
• Limitations and shortcomings
• Complex design and construction
• Wear, breakdown, and maintenance of parts
• Limits on operating speed

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Electronic Implementation

• Stores numerical values as magnetic charges or by
  positioning electrical switches
• Can convert physical movement into electrical
  signals, or vice versa
• World War II impetus for change
• Faster, more reliable, easier to build than
  mechanical counterparts

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Optical Implementation

• Harnesses energy of a moving photon
• Represents data as pulses of light stored
  directly or indirectly by materials that reflect
  or dont reflect light
• Now common in computer networks that cover large
  distances

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Computer Capabilities

• Processing
• Storage
• Communication

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Processor

• Device that performs data manipulation and
  transformation functions
• Computation
• Comparison
• Data movement among memory, mass storage, and
  input/output devices

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Processor Terminology

• Instructions
• Programs
• General-purpose and special-purpose processors
• Formulas and algorithms
• Comparisons and branching

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Storage Capacity

• Types of information to be stored
• Intermediate processing results
• Data
• Programs
• Characteristics of storage devices vary widely
• Cost
• Access speed
• Reliability

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Input/Output Capability

• Must encompass many communication modes
• Sound, text, and graphics (for humans)
• Electronic or optical communication (for other
  computers)

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Computer Hardware
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Central Processing Unit

• General-purpose processor
• Executes all instructions (computation and
  comparison functions)
• Directs all data movement

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CPU Components
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System Bus

• Internal communication channel that connects all
  other hardware devices
• Primary pathway for moving data and instructions
  among hardware components
• Capacity is critical to performance, secondary
  storage, and I/O device performance

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Primary Storage(Main Memory)

• Holds program instructions and data for currently
  executing programs
• Implemented with random access memory (RAM)
• Provides access speed and allows CPU to read or
  write to specific memory locations
• Volatile does not provide permanent storage

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Secondary Storage

• Composed of high-capacity nonvolatile storage
  devices that hold
• Programs not currently being executed
• Data not needed by currently executing programs
• Data needed by currently executing programs that
  does not fit within available primary storage

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Input/Output Devices

• Implement external communication functions
• Human-oriented communication devices(e.g.,
  keyboard, mouse, printer)
• Computer-oriented communication devices(e.g.,
  modem, network interface unit)

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Computer System Classes
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Multicomputer Configurations

• Any organization of multiple computers to support
  a specific set of services or applications
• Common configurations
• Cluster
• Blade
• Grid

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Cluster

• Group of similar or identical computers that
  cooperate to provide services or execute a common
  application
• Connected by high-speed network
• Typically located close to one another
• Advantages scalability and fault tolerance
• Disadvantages complex configuration and
  administration

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Blade

• Circuit board that contains most of a server
  computer a specialized cluster
• Same advantages and disadvantages as a cluster,
  but also
• Concentrate more computing power in less space
• Are simpler to modify

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Grid

• Group of dissimilar computer systems, connected
  by high-speed network, that cooperate to provide
  services or execute a common application
• Computers may be in separate rooms, buildings, or
  continents
• Computers work cooperatively at some times,
  independently at others

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Bigger Isnt Always Better

• Groschs Law (1952) has been rewritten due to
• Multiple classes of computers
• Expanded abilities to configure computers for
  specific purposes
• Increased software costs relative to hardware
  costs
• Large computer databases
• Widespread adoption of graphical user interfaces
• Multicomputer configurations

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The Role of Software

• Translates user requests into machine
  instructions
• Performs complex translation process that bridges
  two gaps
• Human language to machine language (binary)
• High-level abstraction to low-level detail

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Software Types
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System Software Layers

• System management
• System services
• Resource allocation
• Hardware interface

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Operating Systems

• Most important system software component
• Collection of utility programs that provides
• Administrative utilities
• Utility services to application programs
• Resource allocation functions
• Direct control over hardware

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Operating System Functions

• Program storage, loading, and execution
• File manipulation and access
• Secondary storage management
• Network and interactive user interfaces

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Application Development Software

• Programs used to develop other programs
• Types
• Program translators
• Program editors
• Debugging tools
• System development tools

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Economics of System and Application Development
Software

• System software consumes hardware resources
• Cost per unit of computing power has rapidly
  decreased
• Software is more cost-effective when reused many
  times

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Computer Networks

• Set of hardware and software components that
  enable multiple users and computer systems to
  share information, software, and hardware
  resources
• Enables many types of personal communication

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External Resources

• Ability to share data, programs, and hardware
  resources among computers
• Gives modern organizations flexibility to deploy
  and redeploy computing and information resources
  to satisfy rapidly changing needs

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Network Software

• Finds requested resources on the network
• Negotiates resource access with distant resource
  allocation software
• Receives and delivers resources to requesting
  user or program
• May also listen for and validate resource
  requests, and deliver resources via the network

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Network Communication and the Physical Network

• Network communication devices
• Simpler than I/O devices do not need to convert
  data represented electronically into another form
• Must support communication at high speeds
• Physical network
• Complex combination of communication protocols,
  methods of data transmission, and network
  hardware devices

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Summary

• Basic elements of computer system architecture
• Hardware
• Software
• Networks
• Importance of knowing how all components of a
  computer system interrelate as well as their
  internal workings