Structure and Role of the Processor and its Components

Question 1

What do processors contain

Answer 1

ALU (Arithmetic Logic Unit)

Control Unit

PC

CIR

MAR

MBR

SR

Question 2

What is the role of the ALU

Answer 2

To perform arithmetic and logic operations

Question 3

What is the control unit responsible for

Answer 3

Controls the hardware, including I/O and CPU

Controlling the fetch execute cycle

Question 4

What are registers

Answer 4

Small storage locations used to hold data temporarily

Question 5

What are General Purpose Registers

Answer 5

Registers that can be manipulated to perform the role of any other registers

Question 6

List the Special Purpose Registers

Answer 6

Program Counter (PC)

Current Instruction Register (CIR)

Memory Address Register (MAR)

Memory Buffer Register (MBR)

Status Register (SR)

Question 7

What does a Program Counter do

Answer 7

Hold the memory address of the next instruction to be executed in the fetch-execute cycle

Question 8

What does the Current Instruction Register do

Answer 8

Holds the instruction that is currently being decoded and executed by the processor

Question 9

What does the Memory Address Register do

Answer 9

Stores the memory address of an instruction that is to be read from, or the address in memory to which data is to be transferred

Question 10

What is the role of the Memory Buffer Register

Answer 10

Holds the content of a memory location that has been read from or data that is stored to

Place where all communications between the CPU and Memory take place

Question 11

What is the role of the Status Register

Answer 11

Contains a number of bits, the values of which can change to indicate the occurrence of an interrupt

Question 12

What is the clock

Answer 12

A device that generates a timing signal which changes at a regular frequency which regulates all of the actions that take place

Question 13

When is the signal generated by the clock used

Answer 13

To synchronise communication between the components of the processor and the rest of the computer system

Question 14

What happens during the fetch stage of the fetch execute cycle

Answer 14

Content of the PC is copied to the MAR

Content of the MAR is transferred to the main memory by the address bus

Instruction is sent from main memory to the MBR by the data bus

PC is incremented by one

Content of the MBR is copied to the CIR

Question 15

What happens during the decode stage of the fetch execute cycle

Answer 15

Content of the CIR is decoded by the control unit

Decoded instruction is split into two parts - opcode and operands

Question 16

What happens during the execute stage of the fetch-execute cycle

Answer 16

Any data required by the instruction that isn’t present is fetched

The instruction is carried out

Results of any calculations are stored in general purpose registers or main memory

Question 17

What are instructions usually stored in and how

Answer 17

Machine code

Two primary parts - opcode and one or more operands

Question 18

What does the opcode specify

Answer 18

Type of operation that is to be carried out

Question 19

What is the operand

Answer 19

Pieces of data on which the operation is performed

Question 20

What are the two types of addressing modes

Answer 20

Immediate and direct

Question 21

What happens in immediate addressing

Answer 21

The value specified in the operand is to be treated as the actual value

Question 22

What happens in direct addressing

Answer 22

Value specified by an operand signifies a memory address

Question 23

What is an interrupt

Answer 23

A signal sent to the processor by another part of the computer requesting the attention of the processor

Question 24

What happens when an interrupt occurs

Answer 24

It is detected as a change in the content of the status register between the execute and fetch stages of the fetch-execute cycle

Question 25

What are the two approaches used in instruction sets

Answer 25

RISC (Reduced Instruction Set Computer)

CISC (Complex Instruction Set Computer)

Question 26

RISC vs CISC

Answer 26

RISC executes one instruction per clock cycle

CISC - each instruction performs so many actions that it takes several clock cycles to complete

Question 27

What Factors affect Processor Performance

Answer 27

Amount of Cores

Cache Memory

Words

Clock Speed

Bus Width