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What Is Computer Architecture?

Computer Architecture =

Instruction Set Architecture + Machine Organization

2

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

3

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

4

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
- ØData

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 Pennsylvania

during World War II

9

The first practical stored-program computer

The first practical stored-program computer was

EDSAC 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.

10

Eckert and Mauchly later went to business, and built the first commercial computer in the United States, UNIVAC I, in 1951.

UNIVAC I

11

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 singleinstruction set architecture.

12

Supercomputers

The era of vector supercomputers started

in 1976 when Seymour Cray built Cray-1 Vector processing is a type of parallelism whichspeeds 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.

13

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

14

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

16

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.

17

10

11

4G

2G

10

10

1G

512M

Memory

256M

10

9

128M

Itanium®

Microprocessor

64M

10

8

Pentium® 4

16M

Pentium® III

10

7

4M

Pentium® II

1M

10

6

Pentium®

256K

Transistors Per Die

i486™

64K

10

5

i386™

16K

80286

4K

10

4

8080

1K

8086

10

3

4004

10

2

10

1

10

0

’

60

’

65

’

70

’

75

’

80

’

85

’

90

’

95

’

00

’

05

’

10

18

Source: Intel

Digital Systems - Analog vs. Digital

- Analog vs. Digital: Continuous vs. discrete.
- Results--- Digital computers replaced analog computers

19

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.

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.

21

Example

Adding two numbers

High-level language (C)

c = a + b;

Assembly language

LDA 004

ADD 005

STA 006

Machine language

0010 0000 0000 0100

0001 0000 0000 0101

0011 0000 0000 0110

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 algebra23

Boolean or logic operations

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.

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

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.

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).

24

INPU

INPU

XOR AB

OR A+B

AND

A.B

A

A

A

B

B

B

0

0

0

0

0

0

0

0

0

1

0

0

0

1

1

1

0

1

1

1

1

1

1

0

0

0

0

1

1

1

1

1

1

1

1

1

0

1

1

0

TRUTH TABLES

___

A.B

25

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

26

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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