Introduction

Dr. Bernard Chen Ph.D.University of Central Arkansas

Spring 2009

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What Is Computer Architecture?

Computer Architecture = Instruction Set Architecture +

Machine Organization

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Instruction Set Architecture ISA = attributes of the computing

system as seen by the programmer Organization of programmable storage Data types & data structures Instruction set Instruction formats Modes of addressing Exception handling

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Machine Organization Capabilities & performance

characteristics of principal functional units (e.g., registers, ALU, shifters, logic units)

Ways in which these components are interconnected

Information flow between components Logic and means by which such

information flow is controlled

What is “Computer”

• A computer is a machine that performs computational tasks using stored instructions.

A computer consist of … ?

1) Central processing unit (CPU);

2) Random access memory (RAM);

3) Input-output processors (IOP).

These devices communicate to each other through a set of electric wires called bus.

CPU consists of

> Arithmetic logic unit (ALU): Executes arithmetic (addition, multiplication,...) and logical (AND, OR,...) operations.

> Control unit: Generates a sequence of control signals (cf. traffic signal) telling the ALU how to operate; reads and executes microprograms stored in a read only memory (ROM).

> Registers: Fast, small memory for temporary storage during mathematical operations.

RAM stores

> Program: A sequence of instructions to be executed by the computer

  Data

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History of Computers

The world’s first general-purpose electronic computer was ENIAC built by Eckert and Mauchly at the University of Pennsylvania

during World War II. However, rewiring this computer to perform a new task requires

days of work by a number of operators.

ENIAC built by Eckert and Mauchly at the University of Pennsylvaniaduring World War II

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The first practical stored-program computer wasEDSAC built in 1949 by Wilkes of Cambridge University.Now the program in addition to data is stored in the memory so that different problems can be solved without hardware rewiring anymore.

 

The first practical stored-program computer

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Eckert and Mauchly later

went to business, and built

the first commercial

computer in the United

States, UNIVAC I, in 1951.

UNIVAC I

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IBM System/360 series

A commercial breakthrough occurred in 1964 when IBM introduced System/360 series.

The series include various models ranging from $225K to $1.9M with varied performance but with a single instruction set architecture.

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Supercomputers The era of vector supercomputers started

in 1976 when Seymour Cray built Cray-1 Vector processing is a type of parallelism which speeds up computation. We will learn related concept of pipelining in this course.

In late 80’s, massively parallel computers such as the CM-2 became the central technology for supercomputing.

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Another important development is the invention of the microprocessor--a computer on a single semiconductor chip.

Microprocessors

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Microprocessor

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Microprocessors enabled personal computers such as the Apple II (below) built in 1977 by Steve Jobs and Steve Wozniak.

personal computers

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In 1965, Gordon Moore predicted that the number of transistors per integrated circuit would double every 18 months. This prediction, called "Moore's Law," continues to hold true today. The table below shows the number of transistors in several microprocessors introduced since 1971.

Moore’s Law

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Moore’s Law Still Holds

’60 ’65 ’70 ’75 ’80 ’85 ’90 ’95 ’00 ’05 ’10

Tra

nsi

stor

s P

er D

ie

1K4K 16K

64K256K

1M

16M4M

64M

4004

80808086

80286i386™

i486™Pentium®

MemoryMicroprocessor

Pentium® IIPentium® III

256M

Pentium® 4

Itanium®

1G2G4G

128M

Source: Intel

108

107

106

105

104

103

102

101

100

109

1010

1011

512M

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Digital Systems - Analog vs. Digital

0000000000000000011111110000011110001000111110001011011010001011

(a) Analog form (b) Sampled analog form (c) Digital form

Magnetic tape contaning analog and digital forms of a signal.

•Analog vs. Digital: Continuous vs. discrete.

•Results--- Digital computers replaced analog computers

Digital Advantages

More flexible (easy to program), faster, more precise.

Storage devices are easier to implement.

Built-in error detection and correction.

Easier to minimize.

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Binary System

• Digital computers use the binary number system. Binary number system: Has two digits: 0 and 1.

• Reasons to choose the binary system:1. Simplicity: A computer is an “idiot” which

blindly follows mechanical rules; we cannot assume any prior knowledge on his part.

2. Universality: In addition to arithmetic operations, a computer which speaks a binary language can perform any tasks that are expressed using the formal logic.

ExampleAdding two numbersHigh-level language (C)c = a + b;

Assembly languageLDA 004ADD 005STA 006

Machine language0010 0000 0000 01000001 0000 0000 01010011 0000 0000 0110

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Since the need is great for manipulating the relations between the functions that contain the binary or logic expression, Boolean algebra has been introduced.

The Boolean algebra is named in honor of a pioneering scientist named: George Boole.

A Boolean value is a 1 or a 0.A Boolean variable takes on Boolean values. A Boolean function takes in Boolean variables and produces Boolean values.

Boolean algebra

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Boolean or logic operations

1. OR. This is written + (e.g. X+Y where X and Y are Boolean variables) and often called the logical sum. OR is called binary operator.

2. AND. Called logical product and written as a centered dot (like product in regular algebra). AND is called binary operator.

3. NOT. This is a unary operator (One argument), NOT(A) is written A with a bar over it or use ' instead of a bar as it is easier to type.

4. Exclusive OR (XOR).

Written as + with circle around it . It is also a binary operator.

True if exactly one input is true (i.e. true XOR true = false).

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INPU XOR

AB

A B

0 0 0

0 1 1

1 0 1

1 1 0

INPU OR A+B

A B

0 0 0

0 1 1

1 0 1

1 1 1

INPU AND

A.B

A B

0 0 0 1

0 1 0 1

1 0 0 1

1 1 1 0

TRUTH TABLES

___ A.B

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Important identities of Boolean ALGEBRA.

Identity: •A+0 = 0+A = A •A.1 = 1.A = A

Inverse: •A+A' = A'+A = 1 •A.A' = A'.A = 0 •(using ' for not)

+ for OR. for AND

Important identities of Boolean ALGEBRA

Associative: A+(B+C) = (A+B)+C A.(B.C)=(A.B).C

Due to associative law we can write A.B.C since either order of evaluation gives the same answer.

Often elide the . so the product associative law is A(BC)=(AB)C

Important identities of Boolean ALGEBRA

Distributive: A(B+C)=AB+AC Similar to math. A+(BC)=(A+B)(A+C)

Contradictory to math.

How does one prove these laws?? Simple (but long) write the Truth

Tables for each and see that the outputs are the same.

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Important identities of Boolean ALGEBRA.