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Computer Architecture and

Organization

Introduction

Unit I- Fundamentals of computer Architecture

• (^) Introduction and Organization of von Neumann machine
• (^) Instruction formats
• (^) The fetch/execute cycle
• (^) Instruction decoding and execution
• (^) Registers and registers files
• (^) Instruction types and addressing modes
• (^) Subroutine call and return mechanisms
• (^) Programming in assembly language
• (^) I/O techniques and interrupts
• (^) Other design issues

History of Computers

ABACUS 4 th Century B.C. The abacus, a simple counting aid, may have been invented in Babylonia (now Iraq) in the fourth century B.C. This device allows users to make computations using a system of sliding beads arranged on a rack.

CHARLES BABBAGE (1791 - 1871)  Born in 1791, Charles Babbage was an English mathematician and professor.  In 1822, he persuaded the British government to finance his design to build a machine that would calculate tables for logarithms. With^ Charles Babbage's^ creation of the "Analytical Engine", (1833) computers took the form of a general purpose machine.

HOWARD AIKEN (1900 - 1973)  Aiken thought he could create a modern and functioning model of Babbage's Analytical Engine. He succeeded in securing a grant of 1 million dollars for his proposed Automatic Sequence Calculator; the Mark I for short. From IBM. In 1944, the Mark I was "switched" on. Aiken's colossal machine spanned 51 feet in length and 8 feet in height. 500 meters of wiring were required to connect each component.

• The Mark I did transform Babbage's dream into reality and did succeed in putting IBM's name on the forefront of the burgeoning computer industry. From 1944 on, modern computers would forever be associated with digital intelligence.

ENIAC 1946

TRANSISTOR 1948  In the laboratories of Bell Telephone,^ John Bardeen, Walter Brattain and William Shockley discovered the "transfer resistor"; later labelled the transistor. Advantages: increased reliability 1/13 size of vacuum tubes consumed 1/20 of the electricity of vacuum tubes were a fraction of the cost

ALTAIR 1975  The invention of the transistor made computers smaller, cheaper and more reliable. Therefore, the stage was set for the entrance of the computer into the domestic realm. In 1975, the age of personal computers commenced. Under the leadership of^ Ed Roberts^ the Micro Instrumentation and Telemetry Company (MITS) wanted to design a computer 'kit' for the home hobbyist. Based on the Intel 8080 processor, capable of controlling 64 kilobyes of memory, the MITS Altair - as the invention was later called - was debuted on the cover of the January edition of Popular Electronics magazine. Presenting the Altair as an unassembled kit kept costs to a minimum. Therefore, the company was able to offer this model for only $395. Supply could not keep up with demand.

IBM (PC) 1981  On August 12, 1981 IBM announced its own personal computer. Using the^ 16 bit Intel 8088 microprocessor, allowed for increased speed and huge amounts of memory. Unlike the Altair that was sold as unassembled computer kits, IBM sold its "ready-made" machine through retailers and by qualified salespeople.

FIRST GENERATION (1945-1956)  First generation computers were characterized by the fact that operating instructions were made-to-order for the specific task for which the computer was to be used. Each computer had a^ different binary-coded program called a machine language that told it how to operate. This made the computer difficult to program and limited its versatility and speed. Other distinctive features of first generation computers were the use of vacuum tubes (responsible for their breathtaking size) and magnetic drums for data storage.

Vacuum Tube

SECOND GENERATION (1956-1963)  Throughout the early 1960's, there were a number of commercially successful second generation computers used in

• business,
• universities, and
• government from companies such as Burroughs, Control Data, Honeywell, IBM, Sperry-Rand, and others. These second generation computers were also of solid state design, and contained transistors in place of vacuum