1.1.1 Architecture of the CPU

Question 1

Describe what happens in the “fetch” part of the fetch-execute cycle? (3)

Answer 1

1. The address of the instruction to be fetched is placed into the MAR. 2. The instruction is fetched from memory. 3. The instruction is transferred to the MDR.

Question 2

Describe what happens in the “decode” part of the fetch-execute cycle? (1)

Answer 2

1. The instruction is decoded

Question 3

Describe what happens in the “execute” part of the fetch-execute cycle? (1)

Answer 3

1. The decoded instruction is then executed so that the CPU performs continuously

Question 4

Descirbe what happens at the end of the fetch execute cycle? (2)

Answer 4

1. The process is repeated 2. The program counter is incremented

Question 5

What operations does the ALU perform? (1)

Answer 5

1. Arithmetic and logic operations

Question 6

What does the Control Unit (CU) do? (2)

Answer 6

Sends signals to control the fetch execute cycle. (1) Co-ordinates the flow of data through the CPU. (2)

Question 7

What is a CPU register? (1)

Answer 7

1. The section of high-speed memory within the CPU that stores data to be processed.

Question 8

State two features of the MAR? (2)

Answer 8

1. It is a register 2. It stores a single address

Question 9

What is the function of the MAR? (2)

Answer 9

1. Stores the address of the instruction that is going to be fetched 2. Holds the address in memory where data is going to be transferred to

Question 10

What is the function of the MDR? (1)

Answer 10

1. Stores the fetched instruction/ the instruction to be processed

Question 11

What is the function of the Program Counter? (1)

Answer 11

1. Stores the address of the next (or current) instruction to be run

Question 12

What is the function of the Accumulator? (1)

Answer 12

1. Stores the result of calculations/processes