This document provides an overview of computer organization and architecture. It discusses the definition of a computer, generations of computers from mechanical to those using integrated circuits and microprocessors. It describes different classes of computing applications like desktops, servers, supercomputers and embedded systems. It explains the relationship between hardware, system software, and application software. It also summarizes the basic components of a computer like CPU, memory, I/O devices and their functions. Finally, it outlines the steps involved in instruction fetch and execution in a computer.

1. 1
Computer Organization
and
Architecture
By
Dr. Ramesh Babu DR
Professor
Dept. of Computer Science & Engineering
PES Institute of Technology

2. 2
References
1. “Computer Organization”,Carl Hamacher,
Zvonko Vranesic and Safwat Zaky, Fifth
Edition, McGrawHill
2. “Computer Organization and Design”, Davis A
Patterson & John L Hennessy, Third Edition,
Elsevier
3. “Computer Architecture: A Quantitative
Approach”, John L Hennessy & Davis A
Patterson

3. 3
Contents
Today’s Lecture will cover:
- Introduction to Computers
- Various Application of Computers
- Generation of computers
- Classes of Computing Applications
- Understanding Program Performance
- Below your Program
- High-Level Language to the Language of
Hardware

4. 4
Contents
- Inside the Computer
- Communication with Other Computers
- Technologies for Building Processors and
Memories
- Real Stuff : Manufacturing Pentium 4
Chips
- Basic Operational Concepts

5. 5
Definition of a Computer
What is it?
A Computer is a machine capable of
manipulating data in complex,
programmable ways.
wikipedia

6. 6
Generations
• First generation Computer, 1940-1956, defined
by Vacuum tubes.
• Second generation Computer, 1956-1963,
defined by Transistors
• Third generation Computer, 1964-1971, defined
by Integrated Circuits (IC)
• Fourth generation computer, 1971-today, defined
by Microprocessors
• Fifth generation computer, Present and Beyond,
defined by Artificial Intelligence (AI)

7. 7
GENERATION 0 :
MECHANICAL COMPUTERS (1642-1945)
 Abacus
 Pascal’s Mechanical Calculator

8. 8
GENERATION 0 :
MECHANICAL COMPUTERS (1642-1945)
 Leibniz Calculator

9. 9
GENERATION 0 :
MECHANICAL COMPUTERS (1642-1945)
 Programmable devices
 Jacquard’s loom

10. 10
GENERATION 0 :
MECHANICAL COMPUTERS (1642-1945)
 Babbage’s Difference Engine

11. 11
First Generation(1940-1956)
 Stored Program Concept(John von
Neumann)
 Vacuum tubes

12. 12
Second Generation(1956-1963)
 Transistor
 Development of programming languages
(COBOL, FORTRAN)

13. 13
Third Generation(1964-1973)
 IC technology
 Microprogramming, parallelism, pipelining
 Cache memory, Virtual memory

14. 14
Fourth Generation(1973-1985)
 VLSI technology
 Microprocessors
 LAN, WAN, Internet

15. 15
Beyond the Fourth
Generation(1985-??)
 AI
 Parallel processing
 Networking

16. 16
Classes of Computing Applications
• Desktop Computers
 Workstations
 Mainframes
 Supercomputers
 Minicomputers
• Servers
• Embedded computers

17. 17
Desktop Computer
A Computer designed for use by an
individual, usually incorporating a graphics
display, keyboard and mouse

18. 18
Servers
A computer used for running larger
programs for multiple users often
simultaneously and typically accessed
only via network

19. 19
Supercomputers
A class of computers with the highest
performance and cost; they are configured
as servers and typically cost millions of
dollars
- Tsubame
- Earth simulator
- Param
Supercomputer

20. 20
Embedded computer
A computer inside another device used for
running one predetermined application or
collection of software

21. 21
Handheld/Pocket PC PDA Tablet PC
Desktop Laptop

22. 22
Workstation

23. 23
Mainframe

24. 24
Supercomputer

25. 25
Understanding Program
Performance
The performance of a program depends on
a combination of the effectiveness of the
algorithms used in the program, the
software systems used to create and
translate the program into machine
instructions, and the effectiveness of the
computer in executing those instructions

26. 26
Below your Program
Application software
System software
Hardware

27. 27
System Software
Software that provides services that are
commonly useful, including operating
system, compilers and assemblers

28. 28
Operating System
Supervising program that manages the
resources of a computer for the benefit of
the programs that run on that machine

29. 29
Complier
A Program that translates high-level
language statements into assembly
language statements

30. 30
High-Level Language to the
Language of Hardware
Assembler – A program that translates a
symbolic version of instructions into the
binary version
Assembly language A symbolic
representation of machine instruction

31. 31
High-Level Language to the
Language of Hardware
A portable language such as C, Fortran, or
Java composed of words and algebraic
notation that can be translated by a
complier into assembly language

32. 32
Under the covers
Five Classic components of computer
- Input
- Output
- Memory
- Datapath
- Control Processor

33. 33
Input
A mechanism through which the computer
is fed information, such as the keyboard,
mouse, scanners, etc…

34. 34
Output Device
A Mechanism that conveys the result of a
computation to a user or another computer

35. 35
Opening the Box
Motherboard – A plastic board containing
packages of ICs, including processor,
cache memeory, and connectors for I/O
devices such as networks and disks
IC- Also called Chip A device combining
dozens to millions of transistors

36. 36
Opening the Box
Memory – The storage area in which programs are
kept when they are running and that contains
the data needed by the running programs
Central Processor Unit (CPU)
Also called processor. The active part of the
computer, which contains the datapath and
control and which adds numbers, tests numbers,
signals I/O devices to activate, and so on..

37. 37
Datapath – The component of the processor
that performs arithmetic operations
Control – The component of the processor
that commands the datapath, memory, and
I/O devices according to the instructions of
the program

38. 38
DRAM – Memory built as an integrated
circuit, it provides random access to any
location
Cache Memory – A small, fast memory that
acts as a buffer for a slower, larger
memory

39. 39
Last week question
 What is liquid Crystal in LCD display.
 Liquid crystal – substance that has
properties between those of a
conventional liquid and a solid

40. 40
 Liquid crystal flow like a liquid, but have the
molecules in the liquid arranged and oriented in
a crystal-like way.
 LCD Display is a thin, flat display device made
up of any number of color or monochrome pixels
arrayed in front of a light source or reflector.
Each pixel consists of a layer of liquid crystal
molecules suspended between two transparent
electrodes and two polarizing filters, the axes of
polarity of which are perpendicular to each .

41. 41
A safe place for data
Memory – The storage area in which
programs are kept when they are running
and that contains the data needed by the
running programs
Volatile Memory – Storage, such as DRAM,
that only retains only if it is receiving
power

42. 42
Nonvolatile memory – A form of memory
that retains data even in the absence of a
power source and that is used to store
programs between runs. Magnetic disk is
nonvolatile and DRAM is not.

43. 43
 Primary Memory : Also called main
memory. Volatile memory used to hold
programs while they are running; typically
consists of DRAM in today’s computers
 Secondary Memory : Nonvolatile memory
used to store programs and data between
runs; typically consists of magnetic disks
in today's computers

44. 44
Magnetic disk ( Also called Hard disk )
A form of nonvolatile secondary memory
composed of rotating platters coated with
a magnetic recording material

45. 45
Communicating with other
computers
Network
LAN
WAN
Advantages
-Communication
- Resource Sharing
- Nonlocal access

46. 46
Technologies for Building
processors and Memories
Silicon – A natural element which is a
semiconductor
Semiconductor – A substance that does not
conduct electricity well

47. 47
Real Stuff: Manufacturing Pentium 4 Chips
 Silicon ingot
 Slicer
 Blank wafers
 Patterned wafers
 Wafer tester
 Dicer
 Tested dies

48. 48

49. 49
Moore’s law in Microprocessors
4004
8008
8080
8085 8086
286
386
486
Pentium® proc
P6
0.001
0.01
0.1
1
10
100
1000
1970 1980 1990 2000 2010
Year
Transistors
(MT)
2X growth in 1.96 years!
Transistors on Lead Microprocessors double every 2 years
Courtesy, Intel

50. 50
Metrics to evaluate a Computer
Metrics
 Speed – delay, frequency
 Power Dissipation
 Energy to perform a function
 Cost
 Scalability
 Reliability

51. 51
Basic Operational Concepts
To perform a given task, an appropriate
program consisting of a list of instruction is
stored in the memory. Individual
instructions are brought from the memory
into the processor, which executes the
specified operation.

52. 52
Add LOCA, R0
Load LOCA, R1
Add R1, R0

53. 53
Connections between the processor and the memory
Processor
Memory
PC
IR
MDR
Control
ALU
R
n 1
-
R
1
R
0
MAR
n general purpose
registers

54. 54
Terms used
 IR - instruction currently being executed
 PC - memory address of next instruction to
be fetched and executed
 MAR - address of location to be accessed
 MDR - data to be written into or read out of
the addressed location
 Interrupts and ISRs

55. 55
Functions…
 Instruction Register : contains the
instruction that is being executed. Its
output is available to the control circuits,
that generates the timing signals for
control of the actual processing circuits
needed to execute the instruction.

56. 56
 Program Counter : is a register, that
contains the memory address of the
instruction currently being executed.
During the execution of the current
instruction, the contents of program
counter is updated to correspond to the
address of the next instruction.

57. 57
Memory Address Register (MAR) : holds
the address of the memory location to or
from which data is to be transferred.
Memory Data Register (MDR): contains
the data to be written into or read-out of
the addressed memory location.

58. 58
General- purpose Registers : are used
for holding data, intermediate results of
operations. They are also known as
scratch-pad registers.

59. 59
Steps involving instruction fetch
and execution
INSTRUCTION FETCH
 Execution of a program starts by setting
the PC to point to the first instruction of the
program.
 The contents of PC are transferred to the
MAR and a Read control signal is sent to
the memory

60. 60
 The addressed word (here it is the first
instruction of the program) is read out of
memory and loaded into the MDR
 The contents of MDR are transferred to
the IR for instruction decoding

61. 61
INSTRUCTION EXECUTION
The operation field of the instruction in IR is
examined to determine the type of
operation to be performed by the ALU
The specified operation is performed by
obtaining the operand(s) from the memory
locations or from GP registers.

62. 62
 Fetching the operands from the memory
requires sending the memory location address
to the MAR and initiating a Read cycle.
 The operand is read from the memory into the
MDR and then from MDR to the ALU.
 The ALU performs the desired operation on one
or more operands fetched in this manner and
sends the result either to memory location or to
a GP register.

63. 63
 The result is sent to MDR and the address of
the location where the result is to be stored is
sent to MAR and Write cycle is initiated.
 Thus, the execute cycle ends for the current
instruction and the PC is incremented to point to
the next instruction for a new fetch cycle.

64. 64
Bus Structures
 BUS – Group of lines (wires) that serves
as a connecting path for several devices
Single-bus structure

65. 65
Data Bus : It is used for transmission of
data. The number of data lines
correspond to the number of bits in a word.
Address Bus: it carries the address of the
main memory location from where
the data can be accessed.
Control Bus: it is used to indicate the
direction of data transfer and to coordinate
the timing of events during the transfer

66. 66
Bus Structures
Single-bus structure
Two-bus structure

67. 67
Single-bus structure
Memory
Input Output Processor
• Only two units can actively use the bus at any given time
• Devices connected to bus vary in speed

68. 68
Advantages of Single-Bus
Structure
 Low Cost
 Flexibility for attaching peripheral devices
Draw Back
low operating speed
Found in small computers such as
minicomputers and microcomputers.

69. 69
TWO-BUS STRUCTURE
Input
Output
Processor
Memory
I/O bus

70. 70
The bus is said to perform two distinct
functions by connecting the I/O units with
memory and processor unit with memory.
The processor interacts with the memory
through a memory bus and handles
input/output functions over I/O bus.
The main advantage of this structure is good
operating speed but on account of more
cost.

71. 71
Performance
 Performance - measure of how quickly
the computer can execute programs
 Speed – Design of Hardware and its
machine Language
 Best Performance – Design of compiler,
Machine instruction set, and the hardware
in a coordinated way

72. 72
Main
memory Processor
Bus
Cache
memory
Execution depends on all units in a computer system
Processor Time depends on the hardware involved in the execution of
individual machine Instruction

73. 73
Processor Clock
 Processor circuits are controlled by timing
signal called clock
 Clock cycle – regular time interval
 If P – length of one clock cycle is an
important parameters that effects
processor performance
 Hertz (Hz) – cycles per second

74. 74
 500 millions cycles per second – 500 MHz
 1250 millions cycles per second – 1.25 GHz

75. 75
Basic Performance Equation
T =
N x S
R
T – processor time(program execution time)
N – number of instruction executions
S – avg. no. of basic steps to execute 1 machine
instruction
R – clock rate

76. 76
Instruction Set
 RISC ( Reduced Instruction Set Computers)
 CISC ( Complex Instruction Set Computers)

77. 77

78. 78
Multiprocessors and
Multicomputers
 Shared-memory multiprocessor systems
 Message-passing multicomputers