1.1 Systems Architecture

Question 1

Fetch - Decode - Execute cycle

Answer 1

Fetch:
PC is checked for memory address of the next instruction
MAR fetches the instruction from main memory (RAM) and brings it to the MDR
PC Increments by one

Decode:
CU Decodes the instruction

Execute:
Decoded instruction is sent to the CPU so that it is executed
Process is repeated

Question 2

Factors that affects the speed of a CPU

Answer 2

• Clock Speed
• Cache Size
• Number of cores

Question 3

What is Virtual Memory? When is it used?

Question 4

Clock Speed

Answer 4

Measured in Hertz (Number of cycles per second)

Question 5

Cache Size

Answer 5

It is a temporary storage of data and instructions being read from and written to the main memory (RAM)

Stores copy of frequently used instructions

It is quicker than to read from main memory

Question 6

Number of cores

Answer 6

More cores = More FDE Cycles at the same time

Does NOT increase the speed of execution of instruction

Question 7

What is an embedded system?

Answer 7

They are dedicated to a specific task and normally part of a larger system

e.g. DVD Player, Washing Machine, Microwave

Question 8

PC (Program Counter)

Answer 8

Holds the address of the next instruction to be executed in memory

Question 9

(MAR) Memory Address Register

Answer 9

Holds the memory address where data is to be fetched from or written to

Question 10

Accumulator

Answer 10

Holds the result of a calculation

Question 11

(MDR) Memory Data Register

Answer 11

Holds data fetched from memory or to be written to memory

Question 12

(ALU) Arithmetic Logic Unit

Answer 12

Performs arithmetic and logical operations