27 Computer Architecture Interview Questions and Answers (2024)

Blog / 27 Computer Architecture Interview Questions and Answers (2024)

Computer architecture refers to the design and organization of the core components of a computer.

While this information might not be practical for many modern developers...

It is 100% worth understanding.

Not only will it give you a better understanding of what is happening under the hood of the computer...

It will also allow you to show off in interviews as it shows a level of understanding that most candidates don't have these days.

Q1.

What is computer architecture?

Junior

Computer architecture refers to the design and organization of the core components of a computer system, including the central processing unit (CPU), memory, and the system's interconnections. It encompasses the rules and methods that describe the functionality, organization, and implementation of computer systems.
Key aspects include processor design, memory management, data representation, and instruction set architecture. It determines how hardware and software interact to deliver the functional requirements of a computer, influencing aspects like processing speed, power consumption, and cost.

Q2.

What are the three categories of computer architecture?

Junior

System Design: This includes the hardware components within a system, such as data processors, memory controllers, and direct memory access.
Instruction Set Architecture (ISA): This defines the machine code that a processor can execute, as well as the native commands and functions of the processor.
Microarchitecture: This deals with the design of the processor's internal architecture, including data paths, pipelines, and control logic, influencing how it implements the ISA.

Q3.

What are some of the components of a microprocessor?

Junior

Arithmetic Logic Unit (ALU): Performs arithmetic and logical operations.
Control Unit (CU): Directs the operation of the processor, managing and coordinating its components.
Registers: Small, fast storage locations for temporary data or instructions.
Cache Memory: A small-sized type of volatile computer memory that provides high-speed data access to a processor.
Buses: Act as communication systems that transfer data between components inside or outside of a microprocessor.
Clock: Controls the timing of all computer operations.
Instruction Decoder: Interprets and converts instructions into signals for the ALU or other components.

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Q4.

What is the purpose of the CPU cache in computer architecture.

Junior

The CPU cache is a small, high-speed memory unit located between the CPU and main memory. It stores frequently accessed data and instructions to reduce the time it takes to fetch them from slower main memory.
The cache improves performance by reducing memory access latency and increasing the CPU's effective speed.

Q5.

Explain the concept of cache coherence in multiprocessor systems.

Junior

Cache coherence refers to the consistency of data stored in different caches in a multiprocessor system. Maintaining cache coherence is crucial to ensure that all processors see a consistent view of memory.
Techniques like invalidation-based and update-based protocols (e.g., MESI) are used to achieve cache coherence by tracking and propagating changes to shared data.

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Q6.

What is MESI?

Junior

MESI is a cache coherence protocol used in multiprocessor systems. It stands for "Modified, Exclusive, Shared, Invalid," which are the four states a cache line can be in.
The protocol ensures that multiple caches storing copies of the same data remain consistent, and it optimizes performance by reducing the need to write data back to main memory.
Each state indicates the status of the data in the cache line and controls the read/write operations to that data:
- Modified: The cache line is only in the current cache and has been changed from the value in main memory (dirty). This cache is responsible for updating the main memory.
- Exclusive: The cache line is only in the current cache and matches main memory (clean).
- Shared: The cache line may be stored in other caches of the system and matches main memory.
- Invalid: The cache line is invalid or empty.

Q7.

Explain the concept of pipelining in computer architecture.

Junior

Pipelining in computer architecture is a technique where multiple instruction phases are overlapped in execution. It's analogous to an assembly line in a factory: just as each stage in an assembly line works on a different car at the same time, each stage in a pipeline processes a different instruction or data stream simultaneously.
This leads to more efficient use of the processor, as it reduces the time to complete an instruction and increases the overall throughput of the system. The main stages in a typical instruction pipeline include fetching the instruction, decoding it, executing it, and writing back the results.

Q8.

What is the easiest way to determine cache locations in which to store memory blocks?

Mid

The easiest way to determine cache locations for storing memory blocks is through a technique called "Direct Mapping." In direct mapping, each block of main memory maps to exactly one cache line. The specific cache line is determined using a simple formula: (Block address modulo number of cache blocks).
This straightforward method ensures a unique and consistent cache location for each memory block, making the determination process efficient and easy to implement.

Q9.

Explain the difference between RISC and CISC architectures.

Mid

RISC (Reduced Instruction Set Computer) architectures use a smaller set of simple and fixed-length instructions, optimizing for simplicity and execution speed.
CISC (Complex Instruction Set Computer) architectures, on the other hand, have a larger set of complex and variable-length instructions, aiming to reduce the number of instructions needed to perform a task.
RISC architectures typically have a simpler and more streamlined pipeline design, while CISC architectures can perform more complex operations in a single instruction.

Q10.

What is branch prediction in computer architecture.

Mid

Branch prediction is a technique used in computer processors to guess the outcome of a conditional branch instruction before it is executed. Its purpose is to improve the flow in the instruction pipeline.
The processor predicts whether the branch will be taken or not taken and continues execution according to this prediction. If the prediction is correct, this results in improved performance; if incorrect, the pre-fetched and pre-executed instructions are discarded, and the pipeline is corrected, which can cause a delay.

Q11.

Explain the concept of out-of-order execution in modern CPUs.

Mid

Out-of-order execution is a CPU design technique that allows instructions to be executed in a different order than they were originally fetched.
It improves instruction-level parallelism by enabling the CPU to execute independent instructions simultaneously, even if they are not in sequential order. This technique can help utilize the CPU's execution units more efficiently.

Q12.

What is speculative execution in CPU architecture.

Mid

Speculative execution is a technique used by modern CPUs to execute instructions before it is certain they will be needed. It helps improve performance by keeping the CPU busy and reducing the impact of instruction dependencies and stalls.
However, speculative execution can also introduce security vulnerabilities, as seen in the Spectre and Meltdown exploits.

Q13.

Explain the concept of a branch target buffer (BTB) in the context of instruction fetching.

Mid

A branch target buffer (BTB) is a cache-like structure that stores the target addresses of recently executed branch instructions. It helps improve CPU performance by predicting the target address of branches, reducing the delay caused by branch instruction execution.
When the BTB prediction is correct, the CPU can fetch and execute instructions efficiently.

Q14.

Explain the concept of instruction-level parallelism (ILP) in CPUs.

Mid

Instruction-level parallelism (ILP) is the ability of a CPU to execute multiple instructions simultaneously. There are two main types of ILP: data-level parallelism (DLP) and control-level parallelism (CLP).
DLP involves executing multiple data operations in parallel, while CLP involves executing multiple control instructions in parallel. Achieving ILP faces challenges like instruction dependencies, branch prediction, and hardware constraints.

Q15.

Explain the concept of vector processing in CPU architecture.

Mid

Vector processing involves performing the same operation on multiple data elements simultaneously. It differs from scalar processing, which operates on individual data elements one at a time.
Vector processing is advantageous for tasks that involve repetitive mathematical operations on large datasets, as it can significantly improve processing speed through parallelism.

Q16.

What is the purpose of the memory hierarchy's write-back and write-through policies?

Mid

Write-back and write-through are cache management policies. Write-back caches write data to the cache first and later update main memory, improving performance but potentially causing data inconsistency in case of crashes.
Write-through caches write data to both the cache and main memory simultaneously, ensuring data consistency but potentially impacting performance.

Q17.

What are the two hardware methods to establish a priority?

Mid

Daisy Chaining: This method assigns priority based on the physical position of devices on a daisy chain. The closer a device is to the CPU in the chain, the higher its priority.
Parallel Priority Interrupt: In this method, each device is connected to a common bus through its own interrupt line. Priority is established by the hardware, often using a priority encoder, which selects the highest-priority request among all the interrupting devices.

Q18.

Explain the role of a TLB (Translation Lookaside Buffer) in virtual memory systems.

Senior

A TLB is a hardware cache that stores recently used virtual-to-physical address mappings. It speeds up address translation by allowing the CPU to access frequently used translations directly from the TLB, reducing the need to access the page table in main memory.
TLBs are crucial for efficient virtual memory management.

Q19.

What is the purpose of SIMD (Single Instruction, Multiple Data) processing in computer architecture?

Senior

SIMD processing allows a single instruction to operate on multiple data elements simultaneously. It is commonly used in applications that require parallel processing of data, such as multimedia processing, scientific simulations, and graphics rendering, where the same operation is performed on multiple data elements.

Q20.

What is DMA?

Senior

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Q21.

Explain what is horizontal micro code?

Senior

Q22.

What is the difference between little-endian and big-endian byte ordering in computer memory storage?

Senior

Q23.

Explain the concept of superscalar architecture in CPUs.

Senior

Q24.

What is the role of an instruction cache (I-cache) and a data cache (D-cache) in a CPU?

Senior

Q25.

What are the five stages in a DLX pipeline?

Senior

Q26.

What are flip-flops?

Senior

Q27.

What are latches?

Senior