2 Systems Architecture, Fifth Edition Chapter Goals Discuss the development of automated computing Describe the general capabilities of a computer Describe

2Systems Architecture, Fifth Edition

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


Chapter Goals (continued)

• Describe the economic role of system and application development software

• Describe the components and functions of computer networks


Systems Architecture

• Describes structure, interaction, and technology of computer system components

• Capabilities of a computer– Accept numeric inputs

– Perform computational functions

– Communicate results


Automated Computation

• Mechanical– Early computers with limited capabilities

• Electronic– Fast, accurate reliable

• Optical– Fast, accurate reliable


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



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


Optical Implementation

• Harnesses energy of a moving photon• Represents data as pulses of light stored directly or

indirectly by materials that reflect or don’t reflect light

• Now common in computer networks that cover large distances


Computer Capabilities

• Processing• Storage• Communication


Processor

• Device that performs data manipulation and transformation functions– Computation

– Comparison

– Data movement among memory, mass storage, and input/output devices


Processor Terminology

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


Storage Capacity

• Types of information to be stored– Intermediate processing results

– Data

– Programs

• Characteristics of storage devices vary widely– Cost

– Access speed

– Reliability


Input/Output Capability

• Must encompass many communication modes– Sound, text, and graphics (for humans)

– Electronic or optical communication (for other computers)


Computer Hardware



Central Processing Unit

• General-purpose processor– Executes all instructions (computation and

comparison functions)

– Directs all data movement



CPU Components

Arithmetic logic unit (ALU)

• Contains electrical circuits that implement each instruction

Registers • Internal storage locations that can each hold a single instruction or data item

Control unit • Controls movement of data to and from CPU

• Accesses program instructions and issues appropriate commands to ALU


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


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


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



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)


Computer System Classes

Microcomputer • Meets information processing needs of single user

• Examples: PCs, network computers

Midrange computer • Supports many programs and users simultaneously

Mainframe • Handles information processing needs of large number of users and applications

• Designed for large amounts of data storage and access

Supercomputer • Designed for rapid mathematical computation



Multicomputer Configurations

• Any organization of multiple computers to support a specific set of services or applications

• Common configurations– Cluster

– Blade

– Grid


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


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


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


Bigger Isn’t Always Better

• Grosch’s 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


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



Software TypesApplication program

• Stored set of instructions for responding to a specific information-processing tasks

• Used directly by end users

Utility program

• Contains instructions for performing general-purpose tasks

• Usually operates invisibly in the background

System software

• Implements utility functions needed by many application programs

• Allocates computer resources to application programs

• Manages computer resources

• Does not interact with end users



System Software Layers

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



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


Operating System Functions

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


Application Development Software

• Programs used to develop other programs• Types

– Program translators

– Program editors

– Debugging tools

– System development tools


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



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



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


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


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


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

Documents

2 Systems Architecture, Fifth Edition Chapter Goals Discuss the development of automated computing Describe the general capabilities of a computer Describe