Third architecture

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Computers Everywhere

Affect every aspect of our lives. Process the data which makes a modern

society function. Embedded in a huge range of devices. Microcomputers bring computing directly

to almost everyone. Opening up new ways of communication. Breaking down political and national

boundaries.

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Information Systems

A computer is part of an information system» Hardware» Software » Data » People» Procedures

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Hardware and Software

HardwareThe physical components associated with a computer or other system.» CPU» Peripheral Devices

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Hardware and Software

SoftwareThe programs which control the operation of a computer, together with the associated documentation. Divided into system and application software.A program is a set of instructions that tell the computer how to process data to produce the required results.

5Why Learn About Hardware and Software?

Hardware can improve productivity, increase revenue, reduce costs, and provide better service

Managers are expected to know about hardware» To help define business needs» To ask questions and evaluate options

when buying equipment

6Why Learn About Hardware and Software?

Software is indispensable for any computer system

Systems software needed for input, calculations, and output

Application software aids in productivity

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Computer Systems: Integrating the Power of Technology

Choosing the right computer hardware requires understanding its relationship to the information system and needs of the organization

Hardware objectives are subordinate to, but supportive of, the information system and the current and future needs of the organization

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Data and Information

What is data? Data is unorganised facts, numbers,

letters and symbols represented in a formalised manner suitable for communication, interpretation and processing by humans or computers.

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Data and Information

What is information? Information is data which has been

assigned a commonly understood meaning.

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Data and Information

Data:AB34652 22025 46723 45890 98345

Information:Number of Products Sold in November in All Sales Areas

Product South North East West

AB34652 22025 46723 45890 98345

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People

Those who use the information provided by the hardware and software. (end-users)

Those who supply the raw data for processing.

Those who write programs. (programmers)

Those who support the running of the system. (computing officers, support engineers)

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Procedures

The rules or guidelines for the running of the information system and its components.» System manuals» Program manuals

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What is a System?

A system is an organised set of related components established to perform a certain task.

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What is a Computer?

An electronic device that can perform the following tasks:» Respond predictably to input» Store the set of instructions needed to

process the input» Process the input according to these

instructions» Store the results of processing» Output information

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Computer Architecture

Hardware

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Architecture

Architecture is those attributes visible to the programmer» Instruction set » Number of bits used for data representation » I/O mechanisms » Addressing techniques» e.g. Is there a multiply instruction?

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Organization

Organization is how features are implemented» Control signals» Interfaces» Memory technology» e.g. Is there a hardware multiply unit or is it

done by repeated addition?

18Architecture & Organization

All Intel x86 family share the same basic architecture

The IBM System/370 family share the same basic architecture

This gives code compatibility» At least backwards

Organization differs between different versions

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Structure & Function

Structure is the way in which components relate to each other

Function is the Operation of individual components as part of the structure

All computer functions are:» Data processing» Data storage» Data movement» Control

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Setup of a Microcomputer

21Setup of a Microcomputer(contd.)

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Computer Operations

Input Processing Output

External Storage

23Von Neumann Architecture

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Instruction Execution

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Arithmetic Logical Unit

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Computer Organization

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Logical PC structure

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Structure - Top Level

Computer

Main Memory

InputOutput

SystemsInterconnection

Peripherals

Communicationlines

CentralProcessing Unit

Computer

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Structure - The CPU

Computer Arithmeticand Logic Unit

ControlUnit

Internal CPUInterconnection

Registers

CPU

I/O

Memory

SystemBus

CPU

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Hardware Components

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Hardware Components

Central processing unit (CPU)» Arithmetic/logic unit (ALU): performs calculations and

makes logical comparisons» Control unit: accesses, decodes and coordinates data

in CPU and other devices Primary memory: holds program instructions and

data for processing; Random Access Memory chips Secondary storage: long-term storage; magnetic disc

Input and output devices Communications devices

32Microcomputer Structure

Address

bus

ALU

Primary Memory

Input

Output

Secondary Memory

Control Unit

Data

bus

Control

busCPU

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Central Processing Unit

Highly complex electronic circuitry that converts data input to information output

Consist of two parts, control unit and arithmetic / logic unit (ALU)

Control unit interprets and executes a list of instructions which comprise the program

The list of operation that performs the desired task is called a program

34Central Processing Unit (CPU)

The microprocessor operates on a list of stored instructions which are executed in a sequential manner, so called a Stored Program Computer.

Arithmetic / Logic Unit executes arithmetic and logical operations.

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Primary Memory

High speed semiconductor memory used to store the program and also any data values which are associated with it

Directly addressed by the microprocessor and the two principal types are read-only memory (ROM) and read/write memory (RAM)

Also known as the immediate access store or main memory

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Primary Memory

ROM is used only for permanent programs and unchanging data storage

RAM (Random Access Memory) is used to stored programs and data that can change during the operation of the computer

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Secondary Memory

Mass-storage devices, such as disk drivers, are not directly addressable but have large storage capacities at a relatively low cost

The contents must be transferred to the primary memory before the processor can access the information

Also known as the backing store

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Input/Output (I/O) Unit

Contains the interface circuits needed to allow the I/O devices to properly communicate with the computer

Examples of input devices are keyboard, image scanner, mouse ...

Examples of output devices are printer, plotter, monitor ...

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The Bus System

Information is passed between the various units of a computer via a communication subsystem called a Bus.

In practice a microprocessor bus is divided into three groups of signals:

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The Data Bus

A set of wires along which data is transferred between units

Signals are bi-directional, since data can flow into or out of the microprocessor

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The Address Bus

A set of wires along which is sent the binary code (the address) that identifies the memory location to be used

Addresses can only be issued by the microprocessor, so it is uni-directional

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The Control Bus

A collection of special signals that coordinates the activities of the various units

Each type of microprocessor has its own particular set of signals

8-bit microprocessors have 8-bit data bus and usually have 16-bit address bus, which allows them to address 64 Kbytes (216) memory locations

43Internal Architecture of Microprocessor

Microprocessor Types Microprocessors are commonly

characterized by the number of bits they process in a single instruction, which is generally determined by the width of the data path, typically are 4-bit, 8-bit, 16-bit, 32-bit and 64 bit.

44Internal Architecture of Microprocessor

Another major distinction is between single-chip microcomputers (often call microcontrollers) which include a microprocessor, memory, and I/O on the same chip, and general-purpose microprocessors, which require external memory and I/O circuits.

45Internal Architecture of Microprocessor

The Microprocessor The microprocessor may be considered to

comprise the following: A number of registers (temporary storage

elements) which can each hold a number of bits of binary information, typically 8 bits (1 byte) and 16 bits representing program instruction, data, addresses.

Program counter (PC) or Instruction Pointer (IP), is used to hold the address of next instruction to be executed.

46Microprocessor Internal Architecture

Control Unit

Instruction Register

Accum

ulator

Flags General Purpose

Registers

Stack Pointer

Program Counter

Address Buffer

Data Buffer

Arithmetic / Logic

Unit

Control signals

Internal control signals

Address bus Data bus

47Microprocessor Internal Architecture

Instruction Register (IR) is used to hold an instruction whilst it is being decoded (by the instruction decoder) to determine the actions necessary to execute the instruction.

General-purpose registers are a set of specified memory locations within the microprocessor used for holding temporary values awaiting further processing.

48Microprocessor Internal Architecture

Accumulator is a special microprocessor register used to hold one of the operands and also the result of an arithmetic or logical operation.

Stack Pointer (SP) is a special microprocessor register pointing to a stack implemented in the primary memory

Arithmetic / Logic Unit (ALU) is the circuitry which performs arithmetic (+, -, x, / ... ) and logical (AND, OR, NOT, XOR, ...) operations.

49Microprocessor Internal Architecture

Timing and control unit is the circuitry which controls both the internal operation of the microprocessor (the operation of ALU and registers) and the external operation of the complete microcomputer system (memory and I/O read/write).

50Microprocessor Internal Architecture

Flags are single-bit information which indicate some particular aspect of the CPU operation result.

e.g. Z = result is zero, OV = result is overflow,   C = carry or borrow is generated

in addition or subtraction operation