CS-404 Computer Organization & Architecture - 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
   aDiscuss the structure and role of the program counter, instruction register and memory register during a fetch-execute cycle.
   How to answer

   • Define PC, IR, MAR/Memory register and their bit-width/connection
   • Fetch cycle steps: PC->MAR, memory read, IR load, PC increment
   • Execute cycle role: IR opcode decode, address from IR/MAR
   • Diagram of CPU registers connected via bus to memory
2. 7 Marks
   bHow does the control word help in micro-operation execution? Illustrate with an example.
   How to answer

   • Define control word and its fields/select lines
   • How control word enables specific micro-operations in one clock
   • Example encoding e.g., ALU, shifter, load signals
   • Illustration of execution sequence using control word
3. 7 Marks
   aIllustrate the concept of bus structure. How does it aid in CPU and memory communication?
   How to answer

   • Define system bus: address, data, control lines
   • Bus structure diagram connecting CPU, memory, I/O
   • Steps of CPU-memory read/write transfer over bus
   • Role of bus arbitration, width and speed
4. 7 Marks
   bExplain 1's and 2's complement representation for negative numbers with examples.
   How to answer

   • Define 1's complement: invert bits, with example
   • Define 2's complement: 1's complement +1, with example
   • Representation of negative numbers and range
   • Advantage for subtraction/addition
5. 7 Marks
   aDescribe Booth's algorithm for multiplication. Illustrate with a 4-bit example.
   How to answer

   • State Booth's algorithm steps and flowchart
   • Rules for 00, 01, 10, 11 with add/subtract and shift
   • Worked 4-bit multiplication example with A, Q, Q-1, count
   • Conclusion on handling signed numbers
6. 7 Marks
   bCompare fixed point and floating point arithmetic operations with examples.
   How to answer

   • Define fixed-point format and arithmetic example
   • Define floating-point format: mantissa, exponent with example
   • Comparison on range, precision, hardware complexity
   • Applications of each
7. 7 Marks
   aHow does USB differ from SCSI bus in terms of speed, cost and application?
   How to answer

   • Brief architecture of USB vs SCSI bus
   • Compare speed/bandwidth generations
   • Compare cost, cabling, device support
   • Compare typical applications
8. 7 Marks
   bWrite a comparative note on different types of I/O interfaces.
   How to answer

   • List types: serial, parallel, USB, SCSI, PCI etc.
   • Compare data transfer mode, speed, protocol
   • Compare cost and device suitability
   • Summary table of I/O interfaces
9. 7 Marks
   aExplain the working of PCI bus. How does it improve I/O performance?
   How to answer

   • Define PCI bus architecture and signals
   • Working: bus arbitration, burst transfer, plug-and-play
   • Features: 32/64-bit, 33/66 MHz, high bandwidth
   • How it improves I/O throughput vs ISA/EISA
10. 7 Marks
    bDifferentiate magnetic tape, disk and optical storage based on access time, reliability and cost.
    How to answer

    • Characteristics of magnetic tape, disk, optical storage
    • Compare access time: sequential vs direct
    • Compare reliability and durability
    • Compare cost per bit and uses
11. 7 Marks
    aHow does cache memory improve system performance? Explain cache design.
    How to answer

    • Principle of locality and cache operation
    • Cache mapping: direct, associative, set-associative
    • Cache design issues: size, block, replacement, write policy
    • Performance improvement via hit rate and access time
12. 7 Marks
    bWrite a program in Pseudo code to simulate page replacement using LRU.
    How to answer

    • Outline LRU logic and data structures
    • Pseudocode for hit/miss, timestamp/stack update
    • Pseudocode for victim selection and replacement
    • Example walkthrough of page reference string
13. 7 Marks
    aDescribe the structure and working of inter-processor communication and synchronization.
    How to answer

    • Need for inter-processor communication in multiprocessors
    • Structures: shared memory, message passing, interconnection
    • Synchronization mechanisms: semaphores, barriers, locks
    • Diagram of multiprocessor communication
14. 7 Marks
    bCompare RISC and CISC architectures with examples.
    How to answer

    • Define RISC: reduced, fixed-length, load-store with example
    • Define CISC: complex, variable-length with example
    • Compare on instruction set, cycles, hardware, compiler
    • Examples: ARM/MIPS vs x86
15. 14 Marks
    Write a short note on any two from the following.

    1. a)Direct Memory Access
    2. b)Virtual Memory
    3. c)Read Only Memory
    How to answer

    • For DMA: definition, controller, transfer modes
    • For Virtual Memory: paging, address translation
    • For ROM: types, characteristics, uses
    • Diagram/block for any two chosen topics