1.1.1 Structure and Function of the Processor

Question 1

What is the function of the CPU?

Answer 1

Executes instructions using the Fetch-Decode-Execute (FDE) cycle.

Question 2

What are the components of the CPU?

Answer 2

Arithmetic Logic Unit (ALU), Control Unit (CU), Registers, Buses.

Question 3

What does the ALU do?

Answer 3

Performs arithmetic and logical operations.

Question 4

Where are the results of ALU calculations stored?

Answer 4

In the Accumulator (ACC).

Question 5

What does the Control Unit (CU) do?

Answer 5

Directs CPU operations, manages data flow, decodes and executes instructions.

Question 6

What synchronises CPU operations?

Answer 6

The clock.

Question 7

What are registers in the CPU?

Answer 7

High-speed, small storage locations.

Question 8

What is the function of the Program Counter (PC)?

Answer 8

Holds the address of the next instruction.

Question 9

What is the function of the Accumulator (ACC)?

Answer 9

Temporarily stores results of ALU operations.

Question 10

What is the function of the Memory Address Register (MAR)?

Answer 10

Stores the address to read/write from/to.

Question 11

What is the function of the Memory Data Register (MDR)?

Answer 11

Temporarily stores data read from/written to memory.

Question 12

What is the function of the Current Instruction Register (CIR)?

Answer 12

Holds the current instruction (opcode + operand).

Question 13

What are General Purpose Registers (GPR)?

Answer 13

Temporarily store data during execution.

Question 14

What are buses in a CPU?

Answer 14

Set of parallel wires that transfer data/signals.

Question 15

What are the three types of system buses?

Answer 15

Data bus, address bus, control bus.

Question 16

What does the data bus do?

Answer 16

Bi-directional. Carries data/instructions.

Question 17

What does the address bus do?

Answer 17

Carries memory addresses (from MAR to RAM).

Question 18

What does the control bus do?

Answer 18

Carries control signals like memory read/write, clock, interrupt.

Question 19

What are the steps of the Fetch-Decode-Execute cycle?

Answer 19

Fetch, Decode, Execute.

Question 20

What happens in the ‘Fetch’ step?

Answer 20

PC → MAR, instruction to MDR, PC incremented, MDR → CIR.

Question 21

What happens in the ‘Decode’ step?

Answer 21

CIR is split into opcode and operand, decoded by CU.

Question 22

What happens in the ‘Execute’ step?

Answer 22

Instruction is executed (e.g. via ALU or data transfer).

Question 23

What affects CPU performance?

Answer 23

Clock speed, number of cores, cache memory, pipelining.

Question 24

What does clock speed control?

Answer 24

Rate of instruction execution (Hz).

Question 25

What is overclocking?

Answer 25

Increasing clock speed, produces more heat.

Question 26

How do multiple cores affect performance?

Answer 26

Allow simultaneous instruction execution.

Question 27

What is cache memory?

Answer 27

Very fast, small memory storing frequently used data/instructions.

Question 28

Describe L1 cache.

Answer 28

Fastest, smallest (2–64 KB).

Question 29

Describe L2 cache.

Answer 29

Larger, slower than L1 (256 KB–2 MB).

Question 30

Describe L3 cache.

Answer 30

Even larger and slower, shared across cores.

Question 31

What is pipelining?

Answer 31

Overlapping multiple instructions during the FDE cycle.

Question 32

What are the types of pipelining?

Answer 32

Instruction pipelining and arithmetic pipelining.

Question 33

What is the Von Neumann architecture?

Answer 33

Single memory for data and instructions, simpler and cheaper.

Question 34

What is the Von Neumann bottleneck?

Answer 34

Slower data transfer compared to CPU speed.

Question 35

What is the Harvard architecture?

Answer 35

Separate memory and buses for data and instructions.

Question 36

Where is Harvard architecture used?

Answer 36

In embedded systems (e.g. digital watches, microwaves).

Question 37

What architecture do contemporary processors use?

Answer 37

Von Neumann for main memory, Harvard for internal cache.

Question 38

What is assembly language?

Answer 38

Low-level language using mnemonics.

Question 39

What are the parts of an assembly instruction?

Answer 39

Opcode and Operand.