Inside a CPU

Question 1

What is a CPU?

Answer 1

A component that processes almost all data and carries out the FDE cycle. It controls the components of the computer and allows for input/ output.

Question 2

What does the ALU do?

Answer 2

The Arithmetic Logic Unit carries out mathematical calculations and logic operations.

Question 3

What does the Control Unit do?

Answer 3

The Control Unit sends control signals to co-ordinate the different components of the CPU

Question 4

What does the MDR do?

Answer 4

The Memory Data Register (MDR) stores the most recently fetched data from the memory. (The data from the memory address that is held in the MAR)

Question 5

What does the Accumulator do?

Answer 5

The Accumulator stores the results of the calculations made by the ALU/ the executed data.

Question 6

What does the CIR do?

Answer 6

The Current Instruction Register stores the most recently fetched instruction ready for it to be decoded and executed.

Question 7

What does the PC do?

Answer 7

The Program Counter contains the address of the first instruction of in the program to be run and holds the address of the next instruction to be executed (by increasing the address number by one each time)

Question 8

What does the MAR do?

Answer 8

The Memory Address Register stores the address of the instruction or Data to be fetched from the memory. This Address was copied from the PC.

Question 9

What does the main Main Memory do?

Answer 9

The Main Memory (RAM) contains the instructions and data if the programs currently in use. The CPU then fetches the instruction/data from it.

Question 10

What are the 5 special registers found in a Von Neuman architecture CPU?

Answer 10

• MDR (Memory Data Register)
• ACC (Accumulator)
• CIR (Current instruction register)
• PC (Program Counter)
• MAR (Memory Address Register)

Question 11

What are the 3 busses?

Answer 11

Control bus
Address Bus
Data bus

Question 12

What does the Control bus do?

Answer 12

The Control Bus is unidirectional and sends control signals from the CPU coordinate the other components.

Question 13

What does the Address Bus do?

Answer 13

Is unidirectional and carries the memory address of location being written or read to. (Being stored to or read from).

Question 14

What does the Data Bus do?

Answer 14

The Data bus is Bidirectional and carries data to and from the processor, memory and other devices.

Question 15

What does the output device do?

Answer 15

The output device allows information from the computer to be received.

Question 16

What does the input device do?

Answer 16

The input device allows an external device like a keyboard or mouse to interact with the computer and make changes.

Question 17

What is a bus?

Answer 17

High speed internal connections that send signals between the processor and other components.

Question 18

What are the 5 components of a CPU?

Answer 18

CU (Control Unit) 
ALU (Arithmetic Logic Unit
Buses 
Registers 
Cache