EC-504-B Computer System Organization - Jun 2025 Question Paper

Under each question, How to answer lists the points an answer should cover, outlined by CampusPrep from the syllabus. Check the details against your textbook.

1. 7 Marks
   aExplain the Von Neumann model and discuss its components with a suitable diagram. How does this model handle instruction and data processing?
   How to answer

   • Definition of Von Neumann stored-program model
   • Components: memory, ALU, control unit, input/output, bus
   • Neat labelled block diagram
   • Fetch-decode-execute handling of instructions and data in same memory
2. 7 Marks
   bDescribe the phases of the instruction cycle: instruction fetch, decode and execution. Explain the significance of each phase.
   How to answer

   • Definition of instruction cycle
   • Fetch phase: PC to MAR, memory read, IR load
   • Decode phase: control unit interprets opcode
   • Execute phase and significance of each phase
3. 7 Marks
   aExplain various addressing modes in a basic computer. Provide examples to illustrate each mode.
   How to answer

   • Definition of addressing mode and effective address
   • Explain direct, immediate, register, indirect, indexed, etc. modes
   • Example instruction for each mode
   • How operand address is computed in each mode
4. 7 Marks
   bCompare and contrast hardwired and microprogrammed control units. Which one is more flexible and why?
   How to answer

   • Principle of hardwired control: combinational logic, speed
   • Principle of microprogrammed control: control memory, microinstructions
   • Comparison on speed, flexibility, cost, design
   • Conclusion: microprogrammed is more flexible and why
5. 7 Marks
   aDescribe the process of multiplication in the arithmetic unit. What are the challenges in designing a multiplication circuit?
   How to answer

   • Steps of binary multiplication: shift-and-add algorithm
   • Hardware organization: multiplicand, multiplier, accumulator
   • Signed multiplication handling e.g. Booth algorithm
   • Design challenges: speed, area, power, overflow
6. 7 Marks
   bDescribe the micro-instruction format and the function of a micro program sequencer.
   How to answer

   • Fields of micro-instruction: control, next-address, etc.
   • Horizontal vs vertical format
   • Role of microprogram sequencer in sequencing
   • Next address generation and branching
7. 7 Marks
   aDifferentiate between program-controlled, interrupt-driven and Direct Memory Access (DMA) data transfer modes.
   How to answer

   • Program-controlled transfer: polling, CPU overhead
   • Interrupt-driven transfer: interrupt handling
   • DMA transfer: DMA controller, cycle stealing
   • Comparison on CPU involvement, speed, hardware cost
8. 7 Marks
   bExplain the role and operation of an I/O interface in data transfer.
   How to answer

   • Need for I/O interface: speed mismatch, format conversion
   • Functions: buffering, synchronization, addressing
   • Operation steps in data transfer
   • Example of status, data and control registers
9. 7 Marks
   aDifferentiate between half-duplex, and full-duplex data transfer modes. In what scenarios is each mode used?
   How to answer

   • Definition of half-duplex: one direction at a time
   • Definition of full-duplex: simultaneous both directions
   • Comparison on channel, efficiency, cost
   • Typical scenarios/applications for each mode
10. 7 Marks
    bExplain the concept of memory hierarchy and its significance in improving computer performance.
    How to answer

    • Levels of hierarchy: registers, cache, main, secondary memory
    • Diagram of pyramid with speed, cost, size trade-off
    • Locality of reference principle
    • Significance in reducing average access time and cost
11. 7 Marks
    aDescribe the organization and mapping techniques used in cache memory. How does cache improve processing speed?
    How to answer

    • Cache organization: lines, tags, valid bits
    • Mapping techniques: direct, associative, set-associative
    • Hit/miss and replacement concept
    • How cache exploits locality to improve speed
12. 7 Marks
    bExplain memory mapping and its significance. How does memory mapping affect the execution of programs?
    How to answer

    • Definition of memory mapping and address translation
    • Types: cache mapping, virtual to physical mapping
    • Significance in protection, relocation, efficient use
    • Effect on program execution: linking, loading, paging
13. 7 Marks
    aDescribe the principles of pipelining in computer architecture. What are its advantages and limitations?
    How to answer

    • Principle of pipelining: overlapping stages
    • Stages example: fetch, decode, execute, memory, writeback
    • Advantages: throughput, speedup, resource utilization
    • Limitations: hazards - data, control, structural
14. 7 Marks
    bExplain the working of vector processors and their application areas in computer systems.
    How to answer

    • Structure of vector processor: vector registers, pipelines
    • Working: single instruction on multiple data elements
    • Chaining and strip mining concept
    • Application areas: scientific, graphics, AI, signal processing
15. 14 Marks
    Write a short note on any Two:

    1. i)Inter-processor communication in multiprocessor systems
    2. ii)I/O processor in modern computer systems
    3. iii)Micro-operations and Register Transfer Language (RTL)
    4. iv)Floating-point representation
    How to answer

    • For each chosen topic: definition and need
    • Key components / format / diagram
    • Working with example
    • Applications / significance in computer organization