1. Overview of Computer Architecture and Organization
Module I
Overview of Computer Architecture and Organization

2. Structure of IAS Computer

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

6. 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

7. 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

8. 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

9. 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

11. Instruction Cycle of IAS
It consist
Fetch Cycle
Execute Cycle

12. 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.

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

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

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

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

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

18. Performance Measurements

19. Clock Speed Operations of Processor is governed by System clock
Speed of the processor is dictated by pulse frequency of clock
Clock signals are generated by a quartz crystal which generates a constant signal wave when power is applied. This wave is converted to digital voltage and is given to processor

20. Clock Speed Rate of pulses is clock rate or clock speed
One increment of clock is clock cycle
Time between pulses is cycle time
Multiple instructions may get executed simultaneously, hence clock speed alone cannot define performance