Computer Architecture Interview Online Test
Computer Architecture technical interview questions and answers help candidates prepare for core computer science interviews conducted by major IT companies and engineering firms. Topics such as CPU design, pipelines, memory hierarchy, RISC vs CISC, interrupts, caching, and instruction-level parallelism are frequently asked in technical rounds of companies like TCS, Wipro, Infosys, Accenture, and Capgemini. Interviewers test your conceptual understanding, problem-solving ability, and practical knowledge of how computers execute instructions internally.
For engineering students and freshers, strong knowledge of computer architecture is beneficial not only in interviews but also in system-level programming, embedded systems, and hardware-related job roles. This guide provides the most important technical questions with detailed explanations to help you revise core concepts, practice interview-oriented topics, and strengthen your fundamentals. Use these questions to prepare thoroughly and improve your chances of success in competitive exams and placement tests.
Computer science candidates should complement their architecture knowledge with microprocessor concepts and operating system fundamentals
1. Explain the von Neumann architecture and its key components
Answer: The von Neumann architecture consists of a central processing unit (CPU), memory, and input/output systems, with a single memory space storing both data and instructions.
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2. What is the purpose of a cache memory in a computer system
Answer: Cache memory stores frequently accessed data to improve access speed, reducing the time the CPU spends waiting for data from the main memory.
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3. Discuss the difference between RISC and CISC architectures
Answer: RISC (Reduced Instruction Set Computing) uses a small, highly optimized instruction set that allows for faster execution, while CISC (Complex Instruction Set Computing) has a larger set of instructions to accomplish more in fewer lines of code.
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4. What is pipelining and how does it enhance performance
Answer: Pipelining allows multiple instruction phases to be executed simultaneously in different stages of the CPU, improving throughput and utilizing CPU resources more efficiently.
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5. Explain the concept of memory hierarchy
Answer: Memory hierarchy organizes computer memory into a hierarchy based on speed and size, with faster, smaller types like registers at the top, and slower, larger types like hard drives at the bottom.
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6. What are the main functions of an ALU (Arithmetic Logic Unit)
Answer: The ALU performs arithmetic operations (addition, subtraction) and logic operations (AND, OR, NOT) on binary data, serving as a fundamental component of the CPU.
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7. Describe the bus system in computer architecture
Answer: The bus system transmits data between the CPU, memory, and peripheral devices, consisting of address, data, and control buses that handle different types of information.
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8. What is the role of an operating system in managing computer architecture
Answer: The operating system manages hardware resources, handling memory allocation, process scheduling, and input/output operations to enable efficient multitasking and user interaction.
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9. Explain how virtual memory works
Answer: Virtual memory extends the available memory by using disk space to simulate additional RAM, allowing the execution of large applications by swapping data in and out of physical memory.
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10. What are the implications of data hazards in pipelined architectures
Answer: Data hazards occur when instructions that rely on the same data are executed in parallel, potentially causing incorrect results; techniques like forwarding and stalling can mitigate these issues.
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11. Discuss the purpose of instruction set architecture (ISA)
Answer: The ISA defines the supported instructions and their formats for a specific computer architecture, serving as the bridge between software and hardware.
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12. What are the advantages and disadvantages of multicore processors
Answer: Multicore processors allow parallel processing, enhancing performance and multitasking capabilities, but can introduce complexity in programming and resource management.
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13. Explain the concept of instruction pipelining
Answer: Instruction pipelining divides instruction processing into several stages, allowing multiple instructions to overlap in execution and improving CPU throughput.
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14. How does I/O performance affect overall system performance
Answer: I/O performance is critical because slow input/output operations can become a bottleneck, hindering system performance despite fast CPU and memory.
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15. What is the function of the control unit in the CPU
Answer: The control unit orchestrates the execution of instructions by directing the flow of data between the CPU, memory, and I/O devices, managing the timing and control signals.
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16. Describe the role of SIMD and MIMD in parallel processing
Answer: SIMD (Single Instruction Multiple Data) executes the same instruction on multiple data points simultaneously, while MIMD (Multiple Instruction Multiple Data) allows different instructions on different data, catering to diverse processing needs.
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17. What are caches, and how do they improve performance
Answer: Caches store frequently used data temporarily, reducing access times for the CPU by minimizing the need to fetch data from slower main memory.
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18. Explain the impact of clock speed on processor performance
Answer: Clock speed determines how many cycles a CPU can execute per second; higher clock speeds generally indicate better performance, though other factors like architecture also play a role.
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19. Discuss the importance of benchmarking in computer architecture
Answer: Benchmarking measures a system’s performance against standard tests, helping identify bottlenecks, compare hardware, and evaluate improvements in architecture.
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20. What is a race condition in computing
Answer: A race condition occurs when two processes access shared data simultaneously and the final state depends on the timing of their execution, potentially leading to inconsistent results.
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21. How does data flow architecture differ from control flow architecture
Answer: Data flow architecture emphasizes the movement of data between operations without relying on sequential control, while control flow architectures execute instructions in a predetermined sequence.
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22. Explain what an opcode is
Answer: An opcode is a part of the instruction set that specifies the operation to be performed by the CPU, serving as a machine-level representation of commands.
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23. What are threaded processors and their advantages
Answer: Threaded processors can handle multiple threads of execution simultaneously, improving parallelism and resource utilization, especially in multitasking environments.
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24. What are bus contention and its implications
Answer: Bus contention occurs when multiple devices try to use the bus simultaneously, leading to delays and performance degradation, requiring arbitration mechanisms to resolve conflicts.
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25. Explain the significance of pipelining in CPU architecture
Answer: Pipelining in CPU architecture allows for multiple instruction stages to be processed simultaneously, improving the overall throughput of the CPU. It divides the instruction processing cycle into distinct stages, such as fetch, decode, execute, and write-back.
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26. What is the difference between RISC and CISC architectures
Answer: RISC (Reduced Instruction Set Computer) architecture uses a small, highly optimized set of instructions, while CISC (Complex Instruction Set Computer) architecture has a larger set of instructions that are more complex. RISC focuses on efficiency and speed, whereas CISC emphasizes a rich set of instructions.
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27. Explain the concept of cache memory and its levels
Answer: Cache memory is a small, high-speed memory located close to the CPU that stores frequently accessed data and instructions. It is organized into levels: L1 is the smallest and fastest, located inside the CPU; L2 is larger and slower, often on the CPU chip; and L3 is the largest and slowest, shared among cores.
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28. How does virtual memory work in a computer system
Answer: Virtual memory extends the physical memory of a computer by using disk space as an extension of RAM. It allows programs to operate as if they have more memory than is physically available by swapping data between RAM and disk storage.
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29. What is the purpose of an instruction set architecture (ISA)
Answer: An instruction set architecture (ISA) defines the set of instructions that a CPU can execute, including data types, registers, addressing modes, and the instruction format. It serves as the interface between hardware and software.
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30. How do branch prediction techniques improve CPU performance
Answer: Branch prediction techniques enhance CPU performance by guessing the outcome of a conditional operation before it is fully executed, allowing the CPU to continue fetching and executing instructions without waiting for the branch decision.
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31. Explain the concept of out-of-order execution in modern CPUs
Answer: Out-of-order execution allows a CPU to execute instructions as resources become available, rather than strictly in the order they appear in the instruction stream. This increases instruction-level parallelism and overall CPU efficiency.
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32. What is the role of a memory hierarchy in computer architecture
Answer: The memory hierarchy organizes storage systems in a way that balances speed, cost, and capacity. It typically consists of registers, cache, main memory, and secondary storage, with each level providing progressively slower but larger storage.
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33. Describe the function of a CPU control unit
Answer: The CPU control unit is responsible for directing the operations of the processor. It fetches instructions from memory, decodes them, and generates the necessary control signals to execute them. It coordinates the activities of the CPU and other components.
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34. What are the advantages of using multicore processors
Answer: Multicore processors combine multiple processing units (cores) on a single chip, allowing parallel execution of tasks, improving performance, and increasing energy efficiency. They are especially beneficial for multitasking and running parallel applications.
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35. How does the Harvard architecture differ from the Von Neumann architecture
Answer: The Harvard architecture separates the memory for instructions and data, allowing simultaneous access to both, which can improve performance. The Von Neumann architecture, on the other hand, uses the same memory for both instructions and data, potentially leading to bottlenecks.
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36. Explain the significance of SIMD and MIMD in parallel processing
Answer: SIMD (Single Instruction, Multiple Data) involves executing the same operation on multiple data points simultaneously, ideal for tasks like image processing. MIMD (Multiple Instruction, Multiple Data) involves multiple processors executing different instructions on different data, suitable for more complex parallel tasks.
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37. What is the impact of pipeline hazards on CPU performance
Answer: Pipeline hazards occur when the next instruction in the pipeline depends on the result of the previous one, causing delays. There are three types: data hazards, control hazards, and structural hazards. They can reduce the efficiency of the pipeline and slow down overall CPU performance.
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38. How does a superscalar processor improve instruction throughput
Answer: A superscalar processor can issue multiple instructions per clock cycle by having multiple execution units. It can execute several instructions simultaneously, significantly improving instruction throughput compared to scalar processors.
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39. What is the role of a TLB (Translation Lookaside Buffer) in virtual memory
Answer: The TLB is a cache used by the CPU to reduce the time taken to access the memory locations in the virtual memory system. It stores the recent translations of virtual memory to physical memory addresses, speeding up memory access.
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40. Describe the concept of register renaming in CPU design
Answer: Register renaming is a technique used to eliminate false dependencies between instructions by providing unique identifiers for each instruction’s target register. This allows for more efficient use of the CPU’s execution units and reduces pipeline stalls.
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41. How does dynamic voltage and frequency scaling (DVFS) help in power management
Answer: DVFS is a power management technique where the voltage and frequency of a processor are adjusted dynamically based on workload demands. This helps reduce power consumption and heat generation while maintaining performance.
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42. Explain the concept of speculative execution in modern processors
Answer: Speculative execution allows the CPU to guess the direction of branches and execute instructions ahead of time. If the speculation is correct, it speeds up processing; if incorrect, the speculative results are discarded, and the correct path is executed.
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43. What is the purpose of a cache coherence protocol in a multiprocessor system
Answer: A cache coherence protocol ensures that all copies of data in different caches remain consistent. It manages the data exchange between caches in a multiprocessor system, preventing issues where different processors see different values for the same memory location.
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44. How do interrupts improve the efficiency of a CPU
Answer: Interrupts allow a CPU to respond to asynchronous events, such as I/O operations, by temporarily halting the current execution and executing a specific interrupt service routine. This allows the CPU to efficiently handle tasks without constantly polling for events.
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45. What is the role of a bus in computer architecture
Answer: A bus is a communication system that transfers data between components inside a computer or between computers. It connects various parts of a computer, such as the CPU, memory, and I/O devices, enabling them to communicate and share information.
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46. Describe the differences between hardwired control and microprogrammed control in CPUs
Answer: Hardwired control uses fixed logic circuits to control signals within the CPU, leading to faster operation but less flexibility. Microprogrammed control uses a sequence of microinstructions stored in memory to control the CPU, offering more flexibility but slower performance.
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47. What is the significance of parallelism in modern computer architectures
Answer: Parallelism in computer architectures allows multiple operations to be performed simultaneously, significantly improving performance. It can be achieved at various levels, including instruction-level parallelism, data parallelism, and task parallelism.
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48. How does the concept of memory interleaving improve performance
Answer: Memory interleaving is a technique that spreads memory addresses evenly across multiple memory modules, allowing the CPU to access data from different modules simultaneously. This reduces memory access latency and improves overall system performance.
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49. Explain the role of a hypervisor in virtualization
Answer: A hypervisor is software that creates and manages virtual machines by abstracting the hardware and allowing multiple operating systems to run concurrently on a single physical machine. It enables efficient resource utilization and isolation between virtual environments.
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