[#6] – Processor and Memory – Questions

CPU is the brain of a computer system. All major calculations and comparisons performed by a computer are carried out inside its CPU. CPU is also responsible for activating and controlling the operations of other units of a computer system. Hence, no other single component of a computer determines its overall performance as much as its CPU.

In order to be able to evaluate a computer’s capabilities quickly, it is important to know how CPUs are internally structured, how different CPUs differ from each other, and how CPU speed is evaluated.

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Points To Remember:

  • CPU is the brain of a computer system. All major calculations and comparisons performed by a computer are carried out inside its CPU. CPU is also responsible for activating and controlling the operations of other units of the computer system. Hence, no other single component of a computer determines its overall performance as much as its CPU.
  • The two basic components of a CPU are the control unit and the arithmetic logic unit.
  • The control unit (CU) of a computer’s CPU acts as the central nervous system for all other components of the computer. It manages and coordinates the entire computer system including the input and output units. It obtains instructions from the program stored in the main memory, interprets the instructions, and issues signals that cause other units of the system to execute them.
  • The Arithmetic Logic Unit (ALU) of a computer’s CPU is the place where the actual execution of the instructions takes place during data processing operation.
  • Every CPU has built-in ability to execute a set of machine instructions, called its instruction set.
  • As instructions are interpreted and executed by a computer’s CPU, there is movement of information between various units of the computer. In order to handle this process satisfactoriluy and to speed up the rate of information transfer, a number of special memory units called registers are used. These registers are used to hold information on a temporary basis and are part of the CPU (not main memory).
  • The speed of a processor is related directly to a computer’s clock speed. Which is the number of pulses produced per second by the built-in electronic clock. This clock speed is measured in megahertz (MHz) or gigahertz (GHz).
  • The three commonly known processor architectures are CISC (Complex Instruction Set Computer), RISC (Reduced Instruction Set Computer), and EPIC (Explicitly Parallel Instruction Computing).
  • Multicore processor technology enables building of computers with better overall system performance by handling more work in parallel. In this technology, a processor chip has multiple cooler-running, more energy-efficient processing cores instead of one increasingly powerful core. Multiple programs/threads can be run at the same time on a multicore chip each core handling a separate program/thread. To take advantage of multicore chips, applications must be redesigned so that the processor can run them as multiple threads.
  • Every computer has a temporary storage area built into the computer hardware. Instructions and data of a program reside in this area mainly when the CPU is executing the program. This storage space is known as primary storage, main memory, or simply memory.
  • Any storage unit of a computer system is characterized and evaluated based on following properties – storage capacity, access time, cost per bit of storage, volatile, and random access.
  • A primary storage or main memory of a computer system is made up of several small storage areas called locations or cells. Each of these locations can store a fixed number of characters (equal to its word-length in bytes). In these computers, storage space is always allocated in multiples of word-length. On the other hand, in a character-addressable computer each numbered address can store only a single character (A,B,1,2,+,- etc.).
  • Main memory capacity of large computer systems is normally more than that of smaller systems. This capacity is defined in terms of the number of bytes a computer system can store. Memory capacity of a computer system is stated normally in terms of kilobytes (KB), which is equal to 1024 (210) bytes of storage, or megabytes (MB), which is equal to 1,048,576 (220) bytes of storage, or gigabytes (GB), which is equal to 1,073,741,824 (230) bytes of storage.
  • A computer’s main memory is built of volatile RAM chips.
  • A special type of RAM, called read-only memory (ROM), is non-volatile memory chip in which data is stored permanently and cannot be altered by the programmer. There are two types of read-only memory (ROM) – manufacturer-programmed and user-programmed. The latter is commonly known as Programmable Read-Only Memory (PROM) because a user can program it.
  • Once information is stored in a ROM or PROM chip it cannot be altered. However, Erasable Prgrammable Read-Only Memory (EPROM) chips can be reprogrammed to store new information. EPROM chips are of two types – Ultra Violet EPROM (UVEPROM) and Electrically EPROM (EEPROM). EEPROM is also known as flash memory.
  • Cache memory is an extremely fast and small memory between CPU and main memory. Its access time is closer to the processing speed of CPU. It acts as high-speed buffer between CPU and main memory and is used to temporarily store very active data and instructions during processing.

List of Questions

  1. List the main functions of CPU in a computer system.
  2. What are the two main components of CPU of a computer system? List the main functions of each of these components.
  3. Describe the role of decoder of a CPU.
  4. What is a microprocessor?
  5. What is an instruction set of a computer system? Do computers made by different manufacturers generally have the same or different instruction sets?
  6. Machine language programs written for one computer will generally not run on another computer with a different CPU. Explain why.
  7. What is a family of CPU? When do two CPUs belong to the same family?
  8. When do we say that a computer is backward compatible with another computer? How this feature is useful for the users of these computers?
  9. What are registers? Name some commonly used registers and briefly describe the function of each.
  10. What does length of a register mean? What are the commonly used register-lengths in modern computer systems? Why is a larger register length desirable?
  11. List the main steps involved in execution of an instruction by a computer’s CPU.
  12. What is clock speed of a computer system? How does it influence the overall speed of a computer system?
  13. Differentiate between CISC and RISC processors.
  14. List the relative advantages and disadvantages of CISC and RISC processors.
  15. What is a multicore processor? How does it differ from a single-core processor?
  16. Explain the limitations of current transistor technology that has forced processor manufacturers to shift form making more powerful single-core processors to multicore processors.
  17. Explain how a multicore processor can handle the execution of multiple simultaneous tasks more efficiently than a single-core processor.
  18. Multicore processor technology adds to extra work for programmers. Explain why.
  19. List the main advantages and current limitations of multicore processor technology as compared to single-core processor technology.
  20. Why multicore processor technology is also referred to as energy-efficient or power-aware processor technology?
  21. Why software licensing is a key issue with multicore chips?
  22. List the key properties used to characterize and evaluate storage units of computer systems.
  23. Explain the difference between volatile and non-volatile memory. Write an example of each type of memory.
  24. Explain the difference among random access, pseudo-random access, and sequential access storage units. Write an example of each type of storage unit.
  25. Differentiate among a bit, a byte, and a word.
  26. Explain the difference between memory read and write operations.
  27. Explain why it is advantageous to have more number of bit per word instead of having more words of shorter length in the memory architecture of a computer system.
  28. Distinguish between word-addressable and character-addressable computers. Discuss their relative advantages and disadvantages.
  29. How many bytes will be required to store the word ‘MEMORY’ in (a) a character-addressable computer, (b) a word-addressable computer having word-length of 64 bits?
  30. Name some commonly used units for stating memory capacity. Roughly, how many characters does each unit represent?
  31. A computer has 512 MB of memory. How many characters can be stored in its memory at a time?
  32. What is a ROM? Why it is so called? Write few typical uses of ROM.
  33. What is a micro-program? Write an example of a micro-program that is a good candidate for storage in the ROM of a computer system.
  34. Differentiate between PROM and EPROM.
  35. Differentiate between UVEPROM and EEPROM.
  36. What is a flash memory? why it is so called?
  37. Differentiate among RAM, ROM, PROM, and EPROM.
  38. What is a cache memory? How it is different from a primary memory?
  39. Explain how a cache memory helps in improving the overall processing speed of a computer system?
  40. Write short notes on:
    Central Processing Unit (CPU)
    Arithmetic Logic Unit (ALU)
    Storage evaluation criteria
    Memory capacity
    Cache memory
    Volatile and Non-volatile storage
    Fixed and Variable word-length memory
    Processor speed
    Instruction set
    Multicore Processors
  41. Write the full form of the following abbreviations:
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