Computer Architectures Jung H Kim Dept of Systems Engineering

Chapter1. Computing and Computers

Elements of Computers (100-3)*2- (100-5)/3 Brain Control Execute Instruction Data Paper Processor Memory Control Execute Input/ Output Devices Instruction 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) f 1, f 2, …, f n Y 1 = f 1 (x) Y 2 = f 2 (Y 1 ) : Y n-1 = f n-1 (Y n-2 ) Z = f n (Y n-1 ) Derived outputGiven 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