Computer Systems Architecture

G51CSA

Computer Systems Architecture• The study of Computer Architecture is the

study of the organization and interconnection of components of computer systems.

• Computer Architects construct computers from basic building blocks such as memories, arithmetic units and buses.

• From those building blocks the Computer Architect can construct any number of different types of computers.

Lecture 1• Computer Systems• Layers of Abstraction• Computer Systems Hierarchy• History of Computers• John Von Neumann’s machine• IC Technology

Computer• A computer is a device that executes a program.

A program is composed of a set of operations or instructions that the computer can carry out.

• A computer can respond to its input (i.e., data). This action is called conditional behavior and it allows the computer to test data and then, depending on the result or outcome of the test, to choose between two or more possible actions. Without this ability, a computer would be a mere calculator.

• The modern computer is said to be a stored program machine because the program and the data are stored in the same memory system. This facility allows a computer to operate on its own program.

Computer System: Motherboard Level

The Motherboard A system board or main board It connects all system components and

allows input and output devices to communicate with the system unit

It contains chips and many other electronic components

Each IC (Integrated Circuits) chips can contain millions of transistors

Chips are packaged, so that they can be attached to a circuit board such as a motherboard, memory module or card

RAM

Disk drive connector

Parallel Port ConnectorSerial Port ConnectorUSB PortExpansion Slots and Cards

Computer Components: Interconnection

I/O CPU

MEMORY

CPU Organization

ALU

Registers

CU

CPU

Memory

F1DDFFFF 01010101010010101address content

Input/Output

I/O Module

CPU

I/O Devices

Computer System Hierarchy

UserApplication Software

High Level LanguageOperating System

Assembly LanguageMachine Code

Electronic Signal

Layers of abstraction

• Applications Software

• Systems Software

• Hardware

Layers of Abstraction

Hardware Software Interface

From Electrons & Holes to a Multiplayer Video Game

Computer Evolution and Performance (History)

• History is important because it teaches us how the world develops and enables us to understand the forces that control events.

• Zeroth Generation 1791 – 1871 - Mechanical parts

• First generation 1945 - 1955—vacuum tubes, plug boards

• Second generation 1955 - 1965—transistors, batch systems

• Third generation 1965 – 1980—ICs and multiprogramming

• Fourth generation 1980 – present—personal computers

Electro-Mechanical Devices

• There are three types of computing machine: mechanical, electronic, and electro-mechanical. A mechanical device, as its name suggests, is constructed from machine parts such as rods, gears, shafts, and cogs. The old pre-electronic analog watch was mechanical and the automobile engine is mechanical (although its control system is now electronic). Mechanical systems are complicated, can’t be miniaturized, and are very slow. They are also very unreliable.

• Electronic devices use circuits and active elements that amplify signals (e.g., vacuum tubes and transistors). Electronic devices have no moving parts, are fast, can be miniaturized, are cheap, and are very reliable.

• The electro-mechanical device is, essentially, mechanical but is electrically actuated. The relay is an electro-mechanical binary switch (on or off) that is operated electrically. By passing a current through a coil of wire (i.e., a solenoid) surrounding an iron bar, the iron can be magnetized and made to attract the moving part of a switch.

Zeroth Generation Zeroth Generation 1791-1871 – Charles Babbage, an

English mathematician, designed the first machine (analytical engine) that incorporated memory.

It had a mechanical design where wheels, gears, etc were used.

Slow and unreliable Not very popular.

Lady Ada Lovelace (daughter of Lord Byron) wrote the instruction for the machine- unfortunately it was never built

Pascal’s calculator: the Pascaline 1694

First Generation Computers (1945-1955) Computer were built with vacuum tubes – electronic valves

which control the flow of electricity. Electronic tubes were made of glass tubes with circuit inside - the size of light bulbs. Each computer contained a large number of valves. Input was written in punch card. The memory was made of magnetic ring. The language used for programming was machine code consists of 0s and 1s (machine language). No Operating System for these machines.

Disadvantages:Disadvantages: Overheating and burnt out after a while Need to replace the components frequently. Cumbersome, difficult to use and maintain Extremely expensive

ENIAC

A (Very) Brief History of Computers

Vacuum Tubes

1946 ENIAC - background• The first electronic general-purpose digital computer was John W.

Mauchly’s ENIAC, Electronic Numerical Integrator and Calculator, completed in 1945 at the Moore School of Engineering, University of Pennsylvania. ENIAC was intended for use at the Army Ordnance Department to create firing tables (i.e., tables that relate the range of a field gun to its angle of elevation, wind conditions, shell, and charge parameters, etc.).

• The ENIAC used 17,480 vacuum tubes and weighed about 30 tons. ENICA was a decimal machine capable of storing twenty 10-digit decimal numbers. Digits were stored in ring counters that operated rather like the cogwheels of mechanical calculators. A ring counter uses the following encoding scheme.

• IBM card readers and punches implemented input and output operations. Many of the fundamental elements of digital design (e.g., timing circuits, logic circuits, and control circuits) that are now so commonplace were first implemented with the construction of ENIAC. Because ENIAC had 20 independent adding circuits, all running in parallel, the ENIAC could also be called a parallel processor.

Second Generation Computers (1955 – 1965) Computers built with transistors - Much smaller and more

powerful computers Could handle interpreters such as FORTRAN or COBOL –

English like commands. Still relied on punched cards for input and printouts for output. Size of computer still large and expensive. Communication was slow. 1958 - Philco introduces TRANSAC S-2000 First transistorized commercial machine

TX-0 (Transistorised eXperimental computer 0), first transistor

based computer, build at MIT Lincoln Labs. DEC PDP-1, First affordable microcomputer. PDP-8, Cheap, the first to use single bus structure.

Third Generation Computers (1965 – 1980)

Computer manufacturers begin replacing transistors with integrated circuit (IC)

Computers became accessible to a mass audience because they were smaller and cheaper than their predecessors.

Example: IBM 360 series mainframe DEC PDP – 8 Mini Computer (1965)

Fourth Generation Computers (1980 – Present)

Microprocessor – possible to produce a complete processor on one silicon chip.

Microcomputers were introduced – can linked together to form networks – which eventually led to the development of the Internet

Also saw the development of GUIs, mouse and handheld devices.

Example : The 1st Supercomputer was announced - Cray-1

Von Neumann Machine

• In 1945, John Von Neumann designed the EDVAC (Electronic Discrete Variable Automatic Computer).

• Before von Neumann, computer programs were stored either mechanically (on cards or even by wires that connected a matrix of points together in a special pattern like ENIAC) or in separate memories from the data used by the program. Von Neumann introduced the concept of the stored program, an idea so commonplace today that we take it for granted. In a stored program or von Neumann machine, both the program that specifies what operations are to be carried out and the data used by the program are stored in the same memory. You could say that the stored program computer consists of a memory containing both data and instructions in binary form. The control part of the computer reads an instruction from memory, carries it out, and then reads the next instruction, and so on. When each instruction is read from memory, it is able to access memory itself to access any data required by the instruction.

Characteristics:

• Stored Program concept• Main memory stores Instructions and data• ALU operating on binary data. ( Arithmetic

and Logic operations on data ).• The Control unit fetches and interprets the

instructions in memory and causes them to execute.

• Input and output equipment operated by control unit

Structure of von Neumann machine

IC Technology• Small scale integration - 1965 on

—Up to 100 devices on a chip• Medium scale integration - to 1971

—100-3,000 devices on a chip• Large scale integration - 1971-1977

—3,000 - 100,000 devices on a chip• Very large scale integration - 1978 to date

—100,000 - 100,000,000 devices on a chip• Ultra large scale integration

—Over 100,000,000 devices on a chip