Structure and Function of Processor

Question 1

What does the Arithmetic Logic Unit do?

Answer 1

Carries out calculations and logic (Comparisons of binary)

Question 2

What is the Control Unit?

Answer 2

Control Unit is a register in the CPU that controls and co-ordinates the activity of the CPU. Control signals are sent along the control bus between the control unit and the other components of the computer.

Question 3

Registers

Answer 3

Registers are small storage locations used to hold data temporarily. They have high read and write speeds. (Within the processor)

Question 4

Program Counter

Answer 4

Holds the address of the next instruction to be executed

Question 5

Memory Address register (MAR)

Answer 5

stores the address of instructions and data that need to be fetched from memory

Question 6

Memory Data register (MDR)

Answer 6

stores the data which is to be sent or fetched from memory

Question 7

Current instruction register (CIR)

Answer 7

stores the actual instruction that is being decoded

Question 8

Accumulator

Answer 8

stores the result of calculations made by the ALU

Question 9

Interrupt register

Answer 9

generates and detects interrupts

Question 10

Buses

Answer 10

the communication channels between the CPU and the memory and other components.

Question 11

Address Bus

Answer 11

A one directional bus that transmits memory addresses that are used as operands in programming instructions, so that data can be retrieved from main memory

Question 12

Data Bus

Answer 12

A bi-directional path for moving data and instructions between system components

Question 13

Control Bus

Answer 13

A bi-directional bus to transmit command, timing and specific status information between system components

Question 14

System Bus

Answer 14

collective term for address, data and control bus

Question 15

FDE cycle (Fetch, Decode, Execute)

Answer 15

PC
MAR
Address Bus
Memory
Data bus
MDR
CIR
Decode Unit

Question 16

What happens in “Fetch” in the FDE cycle. (1)

Answer 16

1. The address of the next instruction is copied from the PC to the MAR
2. The fetch signal is sent across the control bus. The content of the MAR are transferred across the address bus.
3. The contents of the memory location stored in the MAR are sent across the data bus and stored in the CIR
4. the PC increments by 1

Question 17

What happens in the “Decode” in the FDE cycle. (2)

Answer 17

The contents of the CIR are sent to the CU and divided. The Opcode tells you the instruction to be carried out and the operand stores the address of any data which might be needed, the operand is sent to the MAR and the data is fetched from memory and stored in the MDR

Question 18

What happens in the “Execute” in the FDE cycle. (3)

Answer 18

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

Question 19

What is pipelining?

Answer 19

Pipelining is where the output from one process provides the input for another