Report (CSA)

8/3/2019 Report (CSA)

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John vonNeumann


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born in Budapest, Hungary on December 28,1903

renowned mathematician and computer scientistwho played an important role in computing

technologywrote a report on the stored program concept,known as the First Draft of a Report on EDVAC

died on February 8, 1957, after he was

diagnosed with cancer, he was 54 years old


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The Von-Neumann Machine


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Von Neumann Model


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MEMORY

CONTROL UNIT

MAR MDR

IR

PROCESSING UNIT

ALU TEMP

PC

OUTPUTMonitor

Printer

LED

Disk

INPUTKeyboard

Mouse

Scanner

Disk


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Memory

Basic Operations:

LOAD

read a value from a memorylocation

STORE

write a value to a memorylocation

Interface to Memory:

MAR-Memory AddressRegister

MDR-Memory Data Register

Processing Unit

Functional Units

ALU = Arithmetic and Logic Unit

performs the arithmetic operations

such as addition, subtraction,

multiplication and division, and the

logical operations

Registers

Small, temporary storage

has eight registers (R0, , R7),

each 16 bits wide Word Size

number of bits normally processed

by ALU in one instruction

also width of registers

16 bits


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Input and OutputDevices for getting data into andout of computer memory

Each device has its own interface,usually a set of registers like thememorys MAR and MDR

Some devices provide both inputand output

disk, network

Program that controls access to adevice is usually called a driver.

Control Unitorganize execution of the program

Instruction Register (IR)

- contains the current instruction

Program Counter (PC)

- contains the address of the nextinstruction to be executed

Control unit:

reads an instruction from memory

the instructions address is in the

PC interprets the instruction, generating

signals that tell the other componentswhat to do

an instruction may take manymachine cycles to complete


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The Stored Program Concept

The stored program concept says

that the program is stored with datain the computers memory. Thecomputer is able to manipulate it as

datafor example, to load it fromdisk, move it in memory, and store itback on disk.


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Stored-Program concept

Main memory stores both data and instructions

Arithmetic and logic unit (ALU) capable of operatingon binary data

Control unit, which interprets and executes the

instructions in memory

Input and output (I/O) equipment operated by thecontrol unit


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Early stored-program Computers

SEACStandards Eastern Autom

atic Computer

first-generationelectronic computer, built

in 1950 by

the U.S. National Bureau

Of Standards


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Manchester Mark1

one of the earliest stored

computer program,

developed from the SmallScale Experimental

machine

(SSEM) or

Baby(operational inJune 1948)

Manchester Automatic

Digital Machine or MADM


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SWAC

Standards Western

Automatic Computer

it was the fastest

computer in the world

until the IAS computer

was completed


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Von Neumann Architecture

All computers more or less based on the samebasic design, the Von Neumann Architecture

Model for designing and building computers,

based on the following three characteristics:1) The computer consists of four main sub-systems:

Memory

ALU (Arithmetic/Logic Unit)

Control Unit

Input/output System (I/O)

2) Program is stored in memory during execution

3) Program instructions are executed sequentially


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von Neumannvon Neumann

ArchitectureArchitecture


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The General and Expanded

Structure ofIAS Computer


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The IAS operates by repetitively performingan instruction cycle. Each instruction cycleconsists of two sub cycles.

a) Fetch cycle: the opcode of the nextinstruction is loaded into the IR and theaddress portion is loaded into the MAR

b) Execute cycle: the control circuitry interpretsthe opcode and executes the instruction bysending out the appropriate control signalsto cause data to be moved or an operationto be performed by the ALU


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MBR (Memory Buffer Register) -contains a word to be stored in memory oris sued to receive from memory

MAR (Memory Address Register) -specifies the address in memory of theword to be written from or read into the MBR

IR (Instruction Register) -contains the 8-bit op-code instruction beingexecuted

IBR (Instruction Buffer Register) -employed to hold temporarily the right-hand instructions from a word in memory

PC (Program Counter) -contains the address of the next instruction-pair tobe fetched from memory

AC and MQ (Accumulator and Multiplier Quotient) -employed to holdtemporarily operands and results of ALU operations


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Early IAS Computers

MANIACMathematical Analyzer, Num

rical Integrator, and Computer

or Mathematical

Analyzer, Numerator, Integrator, and Computer

early computer builtunder the directionofNicholas Metropolis

based on the vonN

eumann architecture ofthe IAS


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AVIDAC

Argonne Version of

the Institute's Digital Autom

atic

Computer

built by Argonne National

Laboratory

used in reactorengineering and

theoretical physics

research


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MISTIC

Michigan State Integral

Computer

Michigan State

University's first computer

consistof five sections -

input, memory, arithmetic

processing, control, andoutput


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Instruction Cycle

Fetch Instruction

Start

Execute

Instruction

Instruction cycle =

Fetch cycle + Execution cycleThe basic function performed by a computer

is program execution.

The program (to be executed) consists of a

set of instructions stored in memory

Instruction processing consists of two steps.

a) Fetch Cycle:

Processor reads (fetches) instruction from

memory one at a time is called "fetch cycle"

b)Execution Cycle:

Execution of a fetched instruction is called

"execution cycle"

All instructions and data are contained in

main memory


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Fetch Cycle


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Execute CycleProcessor-memory

data transfer between CPUand main memory

Processor I/O

Data transfer between

CPU and I/O moduleData processing

Some arithmetic or logicaloperation on data

Control

Alteration of sequence ofoperations

e.g. jump

Combination of above


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Interrupt Cycle

Interrupts

interrupt the normal

processing of the

processorInterrupts are providedfor improving theprocessing efficiency

Most external devicesare much slower thanthe processor.


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Classes ofInterrupts

Program interruptsInterrupt generated by some condition that occurs as a result of aninstruction execution. E.g., Arithmetic overflow, division by zero, etc..

Timer interrupts

This allows the operating system to perform certain functions on a regularbasis. E.g., Automatic saving of a document after certain time period.

I/O interruptsGenerated by an I/O controller to signal normal completion of an operationor to signal a variety of error conditions.

Hardware failure interruptsHardware failure interrupts will occur due to power failure, memory parity-error, etc.


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Interrupt Cycle

Added to instruction cycle

Processor checks for interrupt

Indicated by an interrupt signal

If no interrupt, fetch next instruction

If interrupt pending: Suspend execution of current program

Save context

Set PC to start address of interrupt handler routine

Process interrupt

Restore context and continue interrupted program


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Instruction Cycle - State Diagram


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Multiple Interrupts

Disable interrupts Processor will ignore further interrupts whilst

processing one interrupt

Interrupts remain pending and are checked afterfirst interrupt has been processed

Interrupts handled in sequence as they occur

Define priorities Low priority interrupts can be interrupted by

higher priority interrupts When higher priority interrupt has been

processed, processor returns to previous interrupt


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Multiple Interrupts - Sequential


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Multiple Interrupts Nested


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ComputerArchitecture &

Organization

Architecture -attributes visible to the

programmer

_Instruction set, number of bits usedfor data representation, I/O mechanisms,

addressing techniques, etc.

Organization-how features are

implemented

_Control signals, interfaces, memory

technology, etc.


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microprocessor vs. microcontroller

microprocessor

the heart of any normal

computer

also known as a CPU --is

a complete computation

engine that is fabricated on

asingle chip

The first microprocessor

was the Intel 4004,

introduced

microcontroller

is "special purpose

computers

is "embedded" inside

some

other device, dedicated to

one task and run one specific

Program, low-power devices,

dedicated input device and

often (but not always) has a

small LED or LCD display for

out ut


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Make everything as simple as

possible, but not simpler.

Albert Einstein

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