Structure and function of the processor - paper 1

Question 1

What does the ALU do?

Answer 1

Completes all of the arithmetic and logical operations

Question 2

What is the purpose of the control unit?

Answer 2

Directs the operations of the CPU such as:
Controlling and coordinating the activities of the CPU
Managing the flow of data between the CPU and other devices

Question 3

What is a register?

Answer 3

Small memory cells that operate at very high speeds, also store data and all arithmetic, logical and shift operations

Question 4

What are 5 different registers?

Answer 4

Program counter, accumulator, MAR, MDR, CIR

Question 5

What does the program counter do?

Answer 5

Holds the address of the next instruction to be executed

Question 6

What does the accumulator do?

Answer 6

Stores the results from calculations

Question 7

What does the MAR do?

Answer 7

Holds the address of a location that is to be read or written to

Question 8

What does the MDR do?

Answer 8

Temporarily stores data that has been read or data that needs to be written.

Question 9

What does the current instruction register do?

Answer 9

Holds the current instruction being executed, divided up into operand and opcode.

Question 10

What is a bus?

Answer 10

A set of parallel wires that connect two or more components inside the CPU

Question 11

What are the three different busses in the CPU?

Answer 11

Data bus, control bus and address bus

Question 12

What does the data bus do?

Answer 12

It is bi directional bus for transporting data and instructions.

Question 13

What does the address bus do?

Answer 13

Used to transmit the memory address specifying where the data is to be sent or retrieves from.
The width is the number of addressable memory locations

Question 14

What does the control bus do?

Answer 14

This is a bi-directional bus. It is used to transmit signals between internal and external components

Question 15

What is assembly language?

Answer 15

Between machine code and a high level language
Uses shortened versions of words such as ADD for addition

Question 16

What is operand?

Answer 16

Contains the data or the address of the data of the instruction

Question 17

What is opcode?

Answer 17

The type of instruction to be executed

Question 18

What is pipelining?

Answer 18

The process of completing the fetch decode execute cycle of three separate instructions simultaneously.
While one instruction is being executed, another is decoded and another is fetched

Question 19

What happens in the fetch stage of the FDE cycle?

Answer 19

PC goes to MAR
Instruction at location copies to MDR
PC increased by 1
Value of MDR copied to CIR

Question 20

What happens in the decode phase of the FDE cycle?

Answer 20

Contents of the CIR are split into operand and opcode

Question 21

What happens in the execute phase of the FDE cycle?

Answer 21

The decoded instruction is executed

Question 22

What 3 factors affect the CPU’s performance?

Answer 22

Clock speed, number of cores, amount and type of cache memory

Question 23

What are the features of Von Neumann architecture?

Answer 23

Shared memory and data bus used for both data and instructions

Question 24

What are the features of Harvard architecture?

Answer 24

2 separate memories - 1 for instructions and 1 for data.

Question 25

What are the advantages of Von Neumann architecture?

Answer 25

Cheaper to develop as the control unit is easier to design
Programs can be optimised in size

Question 26

What are the advantages of Harvard architecture?

Answer 26

Quicker execution as data and instructions can be fetches in parallel.
Memories can be different sizes which can be a more efficient use of space.

Question 27

What is contemporary processing?

Answer 27

A combination of Harvard and Von Neumann architecture. Von Neumann is used when working with data and instructions in main memory. Harvard is used to divide the cache into instruction cache and data cache.