CS 1.1.1 Structure and Function of the Processor

25 flashcards · Computer Science · by TheoTyson

1. What is the function of the control unit?

   Controls and coordinates the activities of the CPU directing the flow of data between devices, and carrying out the FDE cycle.

2. What is the function of the arithmetic logic unit (ALU)?

   Performs arithmetic and logical operations on the data, including mathematical operations, shift operations and boolean logic operations.

3. What is the accumulator?

   Temporary memory location that stores the results of calculations performed by the ALU.

4. What are registers?

   Small pieces of memory that operate at very high speeds used to store results of operations.

5. What is the function of the program counter?

   Holds the address of the next instruction to be executed, this may be the next sequential instruction or it may follow a branch instruction.

6. What is the function of the current instruction register (CIR)?

   Holds the current instruction being executed.

7. What is an opcode?

   The part of the instruction that says what to do with the data.

8. What is an operand?

   The part of the instruction that refers to the data to be acted on, or the memory location.

9. What is the function of the memory address register (MAR)?

   Holds the address of the memory location from where data or an instruction is fetched from or where it is to be written.

10. What is the function of the memory data register (MDR)?

    Temporarily stores the data read or written from or to the memory.

11. What are buses?

    Sets of parallel wires that connect two or more components, they include the control bus, data bus, and address bus. Connect the CPU to the memory.

12. What is the function of the control bus?

    Controls the timing and status of the components and the buses running between them.

13. What is the function of the data bus?

    A bus that is able to move instructions and data between system components.

14. What is the function of the address bus?

    Transmits the memory addresses of data that is to be stored or retrieved.

15. What happens during the bus cycle?

    When the CPU wants to access main memory, it send the address to memory on the address bus. The data in that location is then returned to the CPU on the data bus. Control signals are sent aliing the control bus.

16. What happens during the fetch phase (FDE)?

    The address of the next instruction is copied from the PC to the MAR. The address is copied to the MDR. The PC is incremented to hold the next address. The contents of the MDR are copied to the CIR.

17. What happens during the decode phase (FDE)?

    The instruction held in the CIR is decoded and split into operand and opcode. Opcode - What hardware is needed to execute it. The operand holds: The address of the data to be used with the operation which is then copied to the MAR. The actual data to be operated on, copied to the MDR. The data to be operated on may be passed to the ALU / Accumulator.

18. What happens during the execute phase (FDE)?

    The appropriate instruction / opcode is carried out on the operand.

19. What happens when the clock speed is changed?

    The system clock generates a series of signals, each CPU operation starts as the clock changes from 0 to 1. The greater the clock speed, the faster the instructions are carried out.

20. What happens when the number of cores is changed?

    Each core has a processor that can fetch and execute instructions independently to each other. More instructions at once, which is more efficient.

21. What is cache?

    A small amount of volatile, expensive, very fast memory inside the CPU. Only stores instructions that are frequently used.

22. What are the levels of cache?

    Level 1 - Extremely fast but small. Level 2 - Fairly fast and medium sized. Level 3 - Fast but large sized.

23. What happens when the amount and type of cache are changed?

    The larger the cache, the more instructions that can be close to the CPU and so can be carried out quickly. The greater the number of cache levels, the more efficient.

24. What is pipelining?

    Breaking up a task into subtasks that can be handled independently. This allows the next instruction to be fetched at the same time as the processor is performing logic operations. It stops idle components, and utilises buffers.

25. What is assembly language?

    Each instruction has an opcode which contains the instruction and the addressing mode. The operand holds the value or address of value.