Introduction Dr. Bernard Chen Ph.D. University of Central Arkansas Spring 2009 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 Data History of Computers The world’s first generalpurpose 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 storedprogram 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 UNIVAC I Eckert and Mauchly later went to business, and built the first commercial computer in the United States, UNIVAC I, in 1951. 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 single instruction 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 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. 13 Microprocessors Another important development is the invention of the microprocessor--a computer on a single semiconductor chip. 14 Microprocessor 15 personal computers Microprocessors enabled personal computers such as the Apple II (below) built in 1977 by Steve Jobs and Steve Wozniak. 16 Moore’s Law 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 Moore’s Law Still Holds 1011 2G 4G 10 Transistors Per Die 10 Memory Microprocessor 109 108 107 4M 512M 1G 256M 128M Itanium® 64M Pentium® 4 16M ® 1M 6 10 256K 64K 4K 16K 5 10 104 80286 i386™ 8080 1K 103 i486™ Pentium III Pentium® II Pentium® 4004 8086 102 101 100 ’60 ’65 Source: Intel ’70 ’75 ’80 ’85 ’90 ’95 ’00 ’05 ’10 18 Digital Systems - Analog vs. Digital 0000000000000000 0111111100000111 1000100011111000 1011011010001011 (a ) A n a lo g fo rm (b ) S a m p le d a n a lo g fo rm (c ) D ig ita l fo rm M a g n e tic ta p e c o n ta n in g a n a lo g a n d d ig ita l fo rm s o f a s ig n a l. •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 21 logic. 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 Boolean algebra 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. 23 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). 24 TRUTH TABLES INPU INPU AND A.B ___ A.B A B A B 0 0 0 1 0 0 0 1 0 1 0 1 0 0 1 1 1 1 0 OR A+B INPU XOR AB A B 0 0 0 0 1 1 0 1 1 1 0 1 1 0 1 1 1 1 1 1 0 25 Important identities of Boolean ALGEBRA. Identity: •A+0 = 0+A = A •A.1 = 1.A = A + for OR . for AND Inverse: •A+A' = A'+A = 1 •A.A' = A'.A = 0 •(using ' for not) 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. Important identities of Boolean ALGEBRA. 29

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