Evolution of Computers: ENIAC and Von Neumann Model

1. Module I Overview of Computer Architecture and Organization

2. History of Computers • First Generation : Vacuum tubes • First General Purpose Computer : ENIAC (Electronic Numerical Integrator and Calculator) • Made in University of Pennsylvania • For World War II

3. ENIAC • Made in Army’s Ballistics Research Laboratory (BRL) • For range and trajectory tables for new weapons • 200 people were employed. • Table preparation took many days

4. ENIAC • Professor John Mauchly and John Eckert proposed first computer • In 1943, proposal was accepted. • ENIAC: • 30 tons • 18000 vacuum tubes • 140KW power consumption • 5000 additions per second

5. ENIAC • ENIAC: • Decimal rather than binary • 20 Accumulators • 10 digit decimal for one accumulator • Ring of 10 vacuum tubes made a digit. • Drawback : Manual programming by setting switches • Completed in 1946

6. ENIAC • First task : feasibility study of Hydrogen bomb • Operated under BRL until 1955 and then it was disassembled.

7. Von-Neumann Machine

8. Von Neumann Model • ENIAC: the major drawback was wired programming • The idea of stored program in memory was introduced by Von Neumann.

9. University Question • What is stored program concept in digital computer? (03 Marks)

10. Stored Program Concept • The programming could be facilitated if the program could be represented in a form suitable for storing in memory alongside data. • Thus • Computer could get its instruction by reading them from memory & • Program could be set and altered by setting values of a portion of memory • This idea is called Stored Program Concept

11. General Structure of Von Neumann Machine

12. Von Neumann Model • It consist of 5 basic units: • Input: Transfers data and program from outside world to machine • Memory: stores both data and instruction • ALU: performs arithmetic and logical operations • Control Unit: fetches, interprets and executes instruction • Output Unit: transfer results to the outside world

13. Von Neumann’s Proposal • This device(computer) perform elementary arithmetic operation (+,-,x,/) and hence it should contain specialized organ called Central Arithmetic part (CA) • The logical control is done by Central Control (CC) organ

14. Von Neumann’s Proposal • For long and complicated sequence of operation, memory (M) is needed. • CA , CC and M correspond to associative neurons . • The effective sensory (afferent) :input • and motor (efferent) : output • The input and output contact thru outside recording medium (R)

15. Von Neumann’s Proposal 4. The device must have organs to transfer information from R to CA , CC and M 5. The device must have organs to transfer information from CA , CC and M to R • All of the today’s computer have this structure & hence referred as Von Neumann Machine

16. Von Neumann: IAS Computer • Memory consist of 1000 words (000 to 999) each of 40 binary digits • They stored data as well as instructions • Data format: Each number is represented by a sign bit and a 39-bit value

17. Von Neumann: IAS Computer • Instruction Format: • Each instruction is of 20 bits ( 2 instructions per location) • Instruction consists of 2 parts : 8-bit opcode and 12 bit address

18. Von Neumann: IAS Computer • Opcode defines operation to be performed • Address part identifies location to store the operand

19. Structure of IAS Computer

21. UQ: Explain the role of different registers like IR,PC,SP,AC,MAR,MDR used in Von Neumann Model [5]

23. Functions of different registers • Memory Buffer Register (MBR) (Data Register) • Store any 40-bit word • Used to store operand of an instruction • It contains a word to be stored in memory or sent to I/O unit or it is used to receive a word from memory or I/O unit

24. Functions of different registers • Memory Address Register(MAR)/ Address Register(AR) • 12 bit register • Specify the address of the memory location to be written into or read from MBR

25. Functions of different registers • Instruction Register(IR) • Holds the opcode of currently executing instruction • Instruction Buffer Register(IBR) • Since 2 instructions are fetched simultaneously, the opcode of the second instruction is stored in IBR • Program Counter(PC) • Store address of the next instruction pair to be executed • Also referred as Instruction Address Register

26. Functions of different registers • Accumulator (AC) and Multiplier Quotient (MQ) • 40 bit register • Used for the temporary storage of operands and results of the ALU operation • E.g. result of multiplication of two 40 bit numbers are stored as Most Significant : AC Least Significant : MQ

36. Instruction Cycle of IAS • It consist • Fetch Cycle • Execute Cycle

37. Fetch Cycle • Opcode of next instruction is loaded into IR and address portion into MAR • This instruction may be taken from IBR or loaded from memory by loading a word into the MBR and then down to IBR,IR and MAR.

38. Execute Cycle • Once opcode reaches IR execution begins • Control circuitry interprets opcode and executes instruction using control signals and ALU

40. Quiz • Which is not a function of computer ? • Data Processing • Data Packing • Data Storage • Data Movement

41. Quiz • Which is not a structural component of computer ? • CPU • Main Memory • Operating System • System Interconnections

42. Quiz • Which is the first type of Programming Language ? • Assembly Level • Machine Level • High Level

43. Quiz • ENIAC stands for • Electronic Numeric Integrator and Computer • Electronic Numeric Integrator and Calculator • Electric Numeric Integrator and Computer • Electric Numeric Integrator and Calculator