Next Generation Computer Architecture: Two Marks Important Questions and Answers

Computer Organization and Architecture

Chapter 6: Next Generation Computer Architecture

 

Two Marks Questions with Answers

 

1. What is a multicore processor ? How does it improve performance ?

Answer: A multicore processor integrates two or more independent processing units (cores) on a single chip. Each core can execute instructions simultaneously, enabling true parallelism. Performance improves because multiple threads/ programs run at the same time rather than increasing the clock speed.

2. Differentiate between hyperthreading and true multicore processing.

Answer: Hyperthreading (SMT) creates logical processors by duplicating some hardware components of a single physical core, allowing two threads to run concurrently. In contrast, a true multicore processor contains multiple physical cores, each capable of independent execution, providing much higher performance gains than hyperthreading.

3. What are the common inter‒core communication methods in multicore systems ?

Answer: Inter‒core communication is achieved through :

• Shared Bus : Simple but becomes a bottleneck for many cores.

• Interconnect Networks : Mesh, ring or crossbar networks for high‒speed communication.

• Shared Memory : Cores communicate by reading/writing to shared memory, making programming simpler.

4. What is cache coherence? Why is it needed in multicore processors ?

Answer: Cache coherence ensures that all cores see a consistent view of shared data stored in caches. It is needed because each core has private caches; without coherence protocols like MESI MOESI, different cores may operate on outdated or inconsistent data.

5. What is the difference between UMA and NUMA memory architectures ?

Answer:

UMA (Uniform Memory Access) : All cores access memory with equal latency.

NUMA (Non‒Uniform Memory Access) : Memory access time depends on the physical location of memory relative to the core. NUMA is common in large multicore and server systems.

6. List two advantages and two challenges of multicore processors.

Answer:

Advantages:

1. Parallel execution of tasks → higher performance.

2. Better energy efficiency since cores run at lower clock speeds.

Challenges:

1. Software must be parallelized to use multiple cores.

2. Cache coherence and synchronization create overhead and complexity.

7. What is a classic multiprocessor system? How is it different from a multicore processor ?

Answer: A classic multiprocessor system uses two or more separate physical CPU chips connected on a motherboard, each with its own hardware. A multicore processor integrates multiple cores on a single chip. Multicore systems have lower communication latency, lower power consumption and are more efficient.

8. Why is thermal management important in multicore processors ?

Answer: Although individual cores operate at lower frequencies, packing many cores on a single chip generates high total heat. Poor thermal management can lead to thermal throttling, performance loss, or hardware damage. Efficient cooling and power control mechanisms are therefore essential.

9. What is a superscalar processor?

Answer: A superscalar processor is a CPU that can issue and execute multiple instructions per clock cycle by using several parallel execution units. It exploits Instruction‒Level Parallelism (ILP) and has hardware like parallel pipelines, advanced decoding, and instruction issue logic.

10. What is the role of the Program Control Unit (PCU) in a superscalar processor ?

Answer: The PCU fetches and decodes multiple instructions simultaneously. It works with instruction schedulers to supply parallel pipelines with a continuous stream of instructions.

11. What is the meaning of instruction issue degree (k) ?

Answer: Instruction issue degree (k) refers to the maximum number of instructions a processor can issue in one clock cycle.

Example : If k = 4 processor can dispatch 4 instructions simultaneously.

12. What are the main types of dependencies that affect superscalar execution?

Answer: Superscalar processors must manage :

• Data dependencies (RAW, WAR, WAW)

• Control dependencies (due to branches)

• Resource conflicts (multiple instructions needing the same unit)

13. What is a structural hazard in superscalar execution?

Answer: A structural hazard occurs when two or more instructions require the same hardware resource at the same time (e.g., ALU, FPU, LSU).

This prevents parallel execution and may cause stalls.

14. What is data dependency checking and why is it important?

Answer: Data dependency checking ensures that instructions issued in parallel are independent.

It prevents hazards like RAW, WAR and WAW, allowing the CPU to issue only safe instructions that won't produce incorrect results.

15. What is an instruction‒issue policy?

Answer: An instruction‒issue policy defines how many instructions and which instructions can be issued per cycle. It determines whether issuing is in‒order, out‒of‒order, or hybrid, affecting overall ILP and CPU performance.

16. What is the difference between in‒order and out‒of‒order issue?

Answer:

• In‒order issue : Instructions are issued in the exact sequence they are fetched.

• Out‒of‒order issue : Instructions are issued based on data availability and resource availability, not strictly in program order.

• Out‒of‒order increases ILP and performance.

17. What is register renaming ?

Answer: Register renaming is a hardware technique that maps architectural registers to a larger set of physical registers to eliminate false dependencies like WAR and WAW.

18. What problem does register renaming solve?

Answer: Register renaming removes false dependencies :

• Anti‒dependency (WAR)

• Output dependency (WAW)

This allows more instructions to execute in parallel and enables out‒of‒order execution.

19. What is a Register Alias Table (RAT)?

Answer: The Register Alias Table (Map Table) stores the mapping between architectural registers and physical registers, ensuring each instruction uses the correct, latest value.

20. How does register renaming improve ILP?

Answer: By eliminating false dependencies, register renaming exposes more parallelism. Hence, more instructions can be issued simultaneously, improving throughput.

21. What is the role of physical registers in renaming ?

Answer: Physical registers act as temporary storage locations for instruction results. Each new instruction is assigned a fresh physical register, avoiding overwriting problems.

22. Why do superscalar CPUs require complex instruction scheduling hardware ?

Answer: Because they must check:

• Data dependencies

• Structural hazards

• Control hazards

Scheduling ensures only independent instructions execute in parallel, avoiding incorrect program behavior.

23. What is the concept of VLIW architecture ?

Answer: VLIW architecture executes multiple independent operations in a single long instruction word. Instead of hardware detecting parallelism at runtime, the compiler statically schedules instructions, resolves dependencies and packs several operations into a single wide instruction that is executed in parallel by multiple functional units.

24. How does VLIW differ from traditional superscalar processors ?

Answer: In superscalar processors, the hardware dynamically detects parallelism, checks dependencies, and schedules instructions. In VLIW, all these tasks are performed by the compiler, enabling simpler hardware. Superscalars have complex, power‒hungry logic, while VLIW relies on static scheduling and fixed‒width instruction packets.

25. What are the main components of a typical VLIW processor ?

Answer: A VLIW processor includes :

• Instruction cache storing long instruction words

• Instruction decoder that splits the long word

• Multiple functional units (ALUS, MAC units, shifters, load/store units)

• A multi‒ported shared register file

• A memory interface for parallel load / store operations

26. Explain static scheduling in VLIW architecture.

 Answer: Static scheduling means the compiler determines the execution order of instructions before runtime. It identifies independent operations, checks all data / control dependencies, and packs parallel operations into a single VLIW packet. No dynamic scheduling logic is needed in hardware.

27. Mention two advantages and two disadvantages of VLIW architecture.

Answer: Advantages:

• Reduced hardware complexity due to no runtime scheduling.

• Lower power consumption and potential for higher clock rates,

Disadvantages:

• Very complex compilers required for dependency checking and instruction packing.

• Code expansion occurs when parallel slots remain unused, increasing memory size.

28. What is meant by 'explicit parallelism' in VLIW processors ?

Answer: Explicit parallelism means each operation inside a VLIW instruction is directly mapped to a specific functional unit. The compiler assigns operations explicitly, so all units execute their operations in the same clock cycle without needing hardware to detect parallelism.

29. Why does VLIW architecture suffer from compatibility issues?

Answer: VLIW scheduling depends on specific processor characteristics such as functional unit count and instruction latency. Code compiled for one VLIW implementation may not work efficiently‒or at all‒on another, making compiled code non‒portable across different VLIW processors.

30. List major application areas where VLIW architecture is used.

Answer: VLIW processors are widely used in:

• Digital Signal Processing (DSP) for MAC‒heavy operations

• Multimedia processing such as audio/video encoding

• Scientific and numerical computing

• Embedded systems requiring low power and parallel execution

31. Define a multiprocessor system and state one of its key characteristics.

Answer: A multiprocessor system contains two or more separate physical CPUs that share common system resources such as memory and I/O devices. A key characteristic is that each processor may have its own private cache but they operate concurrently to execute different tasks in parallel.

32. Write any two differences between a multicore system and a multiprocessor system.

Answer:

• A multicore system has multiple cores on a single chip, while a multiprocessor system has wd multiple separate CPU chips.

• Multicore systems offer low communication delay since cores are close; multiprocessors have higher communication delay due to physical separation.

33. Explain shared L2 cache and give one advantage of using it in multicore systems.

Answer: A shared L2 cache is a higher‒level cache accessible by all cores on the chip.

Advantage : It reduces overall miss rate because threads from multiple cores may benefit from shared data and cache coherency issues become limited to the L1 cache only.

34. List two advantages and two disadvantages of multicore systems.

Answer: Advantages :

1. Higher performance at lower clock frequencies.

2. Energy efficient with reduced heat generation.

Disadvantages :

1. Requires parallel programming to fully utilize cores.

2. Not all applications benefit speedup is rarely linear.

35. What is constructive interference in shared caches?

Answer: Constructive interference occurs when multiple cores benefit from shared cached data, reducing cache misses overall. Shared caches prevent duplication of shared data and allow dynamic allocation of cache space depending on workload.

36. Mention two advantages of multiprocessor systems.

Answer:

1. High throughput due to multiple physical CPUs working simultaneously.

2. High reliability ‒ failure of one CPU does not stop the system (fault tolerance).

37. Why do multiprocessor systems face higher communication delays compared to multicore systems?

Answer: In multiprocessor systems, CPUs are physically separated on the motherboard, so communication occurs through shared buses or interconnects, causing higher latency. In multicore systems, cores are located on the same chip, enabling faster data exchange.

38. What is a GPU ?

Answer: A GPU (Graphics Processing Unit) is a specialized processor designed for parallel processing tasks, primarily used for rendering graphics and high‒performance computing tasks like AI, ML and simulations.

39. List any two key features of GPU.

Answer:

• High parallel processing capabilities using thousands of cores

• High memory bandwidth using GDDR memory

40. How is GPU architecture different from CPU architecture ?

Answer: GPU has many smaller cores for parallel execution, while CPU has fewer powerful cores optimized for sequential processing.

41. Name any two general‒purpose applications of GPUs.

Answer:

• Deep learning model training

• Scientific simulations

42. What is CUDA?

Answer: CUDA (Compute Unified Device Architecture) is a parallel computing platform and programming model developed by NVIDIA for general‒purpose computing on GPUs.

43. Mention two advantages of using CUDA.

Answer:

• High‒performance parallel computing

• Scalable across various NVIDIA GPUs

44. What is a CUDA kernel ?

Answer: A CUDA kernel is a function written in CUDA C/C++ that runs on the GPU in parallel across multiple threads.

45. Define the terms "host" and "device" in CUDA.

Answer: In CUDA, the CPU is called the host and the GPU is called the device. Their respective memories are host memory and device memory.

46. What is the hierarchical structure of CUDA threads?

Answer: CUDA threads are organized into threads, blocks, and grids.

47. Name any two types of CUDA memory.

Answer:

• Global memory

• Shared memory

48. What is the role of the Load/Store Unit (LSU) in CUDA architecture?

Answer: It manages the transfer of data between registers, shared memory, and global memory.

49. Differentiate between Shared Memory and Global Memory.

Answer: Shared Memory is faster and accessible within a thread block; Global Memory is larger but slower and accessible by all threads.

50. What is dynamic parallelism in CUDA ?

Answer: It allows a CUDA kernel to launch other kernels during execution, enabling recursive or adaptive algorithms.

51. State one limitation of CUDA.

Answer: CUDA works only on NVIDIA GPUs, limiting hardware compatibility.

52. Give one application area of CUDA In real‒world computing.

Answer: Medical imaging ‒ e.g., processing MRI and CT scan data.

53. What is an Artificial Neural Network (ANN)?

Answer: An ANN is a computing model inspired by the human brain, made up of interconnected nodes (neurons) that work together to recognize patterns, learn from data, and make predictions.

54. Why do ANNS need specialized hardware ?

Answer: ANNs involve extremely large numbers of Multiply‒Accumulate (MAC) operations, matrix and vector computations, and heavy parallel processing. CPUs perform these slowly and use more power, so specialized hardware like NPUs is required.

55. Why are CPUs not suitable for ANN processing ?

Answer: CPUs are designed for general‒purpose, sequential tasks. They cannot efficiently handle the huge parallel computations required by ANNs, resulting in high energy consumption and slow performance.

56. What led to the development of NPUs ?

Answer: The growing need for high‒speed AI processing with low power consumption, especially in smartphones, IoT, and embedded devices, led to the development of NPUs.

57. What is a Neural Processing Unit (NPU)?

Answer: An NPU is a specialized chip designed to perform AI and machine learning operations, especially matrix multiplication, convolutions, and activation functions faster and more efficiently than CPUs or GPUs.

58. How is an NPU better than a GPU for Al tasks?

Answer: While GPUs are good at general parallel tasks, NPUs are specialized only for AI computations. They feature:

• Optimized matrix and convolution units

• Lower precision arithmetic

• Faster inference with less power

This makes NPUs more efficient for AI workloads.

59. Which Al operations are accelerated by an NPU ?

Answer:

• Matrix multiplications

• Convolutions

• Activation functions (ReLU, sigmoid)

60. Mention any two key characteristics of NPUs.

Answer:

• Highly optimized parallel processing

• Low precision arithmetic for faster and energy‒efficient AI computation

61. Why is efficient memory access important in NPUS ?

Answer: Neural networks move large data (weights, activations). NPUs use:

• High‒bandwidth memory

• Optimized memory hierarchy

• Dataflow architecture

This reduces bottlenecks and ensures continuous data flow, improving speed and efficiency.

62. What is "on‒device Al" and why is it important?

Answer: On‒device AI means AI processing occurs directly on the device instead of cloud servers.

Benefits:

• Reduced latency (faster results)

• Better privacy (data stays on device)

• Lower bandwidth usage

• Offline capability

63. Explain any three real‒world applications of NPUs.

Answer:

• Autonomous vehicles : Real‒time object detection, lane tracking

• Smart home devices : Smart cameras, voice recognition

• IoT/Edge devices : Industrial automation, predictive maintenance

Q.64 Explain the concept of Al Processing Chips (AI PCs)

Answer: AI Processing Chips, or AI PCs, are computing systems that include specialized hardware accelerators like NPUS, GPUs, and tensor accelerators.

They perform AI tasks such as image recognition, NLP, translation, predictive analytics, and noise cancellation locally on the device without relying on cloud servers.

This makes Al tasks faster, private and energy‒efficient.

65. What are the specialized hardware components used in Al PCs ?

Answer: AI PCs typically include:

• CPU‒Manages general‒purpose tasks and operating system functions

• GPU ‒ Performs parallel matrix and vector computations for deep learning.

• NPU ‒ Accelerates neural network inference with low power usage.

• AI engine / Tensor accelerator‒ Performs fast tensor and matrix operations for deep learning.

66. State the major benefits of Al PCs.

Answer:

• High performance for AI tasks

• Better energy efficiency (lower power)

• Low latency due to on‒device AI

• Improved privacy (data stays on device)

• Enhanced user experience (noise cancellation, auto‒framing, etc.)

67. List the commonly used Al processing chips.

Answer:

• Intel Core Ultra (with NPU)

• AMD Ryzen AI

• Apple M‒series (with Neural Engine)

• Qualcomm Snapdragon (Hexagon NPU)

• Google Tensor (Pixel phones)

68. Explain the major application areas of Al PCs.

Answer:

• Al‒based productivity tools (Copilot, ChatGPT local inference)

• Smart video conferencing (noise removal, auto‒framing)

• Content creation (editing, generative AI)

• Gaming enhancements

• Real‒time translation and voice assistance

• On‒device face and biometric authentication

69. What is meant by "Next Generation Processors" ?

Answer: Next‒generation processors are advanced SoCs that integrate multiple specialized units (CPU, GPU, NPU) on a single chip to deliver high performance, parallelism, and energy efficiency for AI, ML and real‒time computing.

70. What is heterogeneous architecture ?

Answer: Heterogeneous architecture combines different types of processing cores ‒ CPUs, GPUs, NPUS ‒ on a single chip.

Each core is optimized for a specific task, increasing performance and efficiency.

71. Give one example each of next‒generation processors and their key components.

Answer:

• Apple M‒series : Unified CPU + GPU + Neural Engine

• Intel Core Ultra : P-cores + E‒cores + Integrated NPU + Arc GPU

• NVIDIA H100 : Tensor cores + HBM memory + high‒end GPU

• Snapdragon : CPU + Adreno GPU + AI Engine

72. List major application areas of next‒generation processors.

Answer:

• Real‒time AI (translation, speech recognition, generative AI)

• Media processing and graphics rendering

• Gaming and immersive experiences

• Edge computing (robots, autonomous vehicles, IoT)

• Industrial automation requiring low‒latency responses