Computer Architectures

Jung H Kim

Dept of Systems Engineering

Chapter1.Computing and Computers

Elements of Computers

(100-3)*2-(100-5)/3

BrainControl

Execute

Instruction

Data

Data Paper

Processor

MemoryControl

Execute

Input/ Output

Devices

Instruction

Data

Data

Every Computer Must Have the Following Components

1. A processor capable of control and execute programs.

2. A memory for saving programs and data.

3. A means of transferring information between the memory and a processor and between the computer and outside world.

Computation

Z = f(x)

in order to evaluate f(x), express x as a sequence of function(or instruction set)

f1, f2, … , fn

Y1 = f1(x)

Y2 = f2 (Y1)

:

:

Y n-1 = f n-1(Y n-2)

Z = f n(Y n-1)

Derived output

Given input

Limitation of Computers

1. The machine should not store the answers to all possible problems.

2. The machine should only be required to solve problems to which a solution procedure or a program can be given

3. It should process information at a finite time.

Touring Machine ( reasonable computing machine)

:A function f is computable if f(x) can be executed by any specified x in a finite number of steps.

… … MemoryX

P

Limitation of Computers

Unsolvable Problem

Goldbach’s conjecture

: Every even integer greater than 2 is the sum of exactly two prime number

such as 8=3+5 and 12=5+7.

It is not known if the conjecture is true for every even integer, nor is any

reasonable procedure known to determine whether the conjecture is true.

Limitation of Computers

Intractable Problem Factors : the nature of the given problem and computer power ) Example. Traveling sales problem

The brute-force approach : n! The best algorithm : exp(n)

Two questions in the difficulty of the algorithm

1.Space complexity : How much memory space is needed to execute it? 2.Time complexity : How much time is needed to execute it?

The VLSI Era

VLSI(Very Large Scale Integration)

LSI(Large Scale Integration)

MSI(Medium Scale Integration)

SSI(Small Scale Integration)

: profound impact on computer design and application

Current VLSI : photolithography technique

Ex)

CPU on a VLSI chip

Playstation 2 on a VLSI chip

Wafer scale integration( WSI )

The VLSI Era

CISC( Complex Instruction Set Computers )Intel 80x86, Motorola 680x0

: Execution of even a small percentage of complex instructions can reduce overall performance

RISC( Reduced Instruction Set Computers) IBM 6600/ SUN SPARC

Von Neumann bottle neck : CPU-memory speed disparity It takes CPU about 5 times longer to obtain a word from memory

than from one of internal registers -- how to reduce the bottle neck: cache memory, interleaved