1.1 System Architecture

Question 1

Define general purpose computer

Answer 1

A computer designed to be able to carry out a range of actions and tasks, use multiple applications

Question 2

Example of applications

Answer 2

Accessing internet, storing and retrieving data, using word processing software

Question 3

Examples of general purpose computers

Answer 3

Smartphone, smart tablet, gaming consoles, PC

Question 4

What is the basic computer model?

Answer 4

Input => Process (or storage) => output

Question 5

Explain the basic computer model

Answer 5

Data is input, processed by the CPU and then either output or sent to secondary storage. Data is sent to primary memory (RAM) whilst being processed.

Question 6

Examples of input devices

Answer 6

Touchscreen, controller, keypad, mouse

Question 7

Examples of output devices

Answer 7

Touchscreen, speaker, display

Question 8

Examples of storage devices

Answer 8

RAM, ROM SSD USB drive, hard disk/drive

Question 9

Von Neumann Architecture definition

Answer 9

Common organisation of computer where instructions and data are stored in the same memory

Question 10

explain function and purpose of ALU

Answer 10

• ALU is the arithmetic logic unit
• definition = component of CPU that performs logic and arithmetic calculations
• can do arithmetic (+,-,/,x), binary shifts and logic operations such as AND or NOT

Question 11

Explain function and purpose of CU

Answer 11

• CU is the control unit
• definition = component of CPU that coordinates CPU activity
• fetches and decodes instructions and data from memory
• sends out control signals that control how data moves around CPU and memory

Question 12

Explain function and purpose of cache

Answer 12

• definition = a small area of memory near CPU that can be accessed quickly and is used to store frequently used data or instructions

Question 13

Define fetch-execute cycle

Answer 13

The basic operation of the CPU - it continually fetches, decodes and executes instructions stored in memory

Question 14

Explain fetch-execute cycle’s fetch section

Answer 14

• each instruction is stored by an address in RAM.
• address copied from PC to MAR
• MAR has address so CU sends control signal to RAM and fetches the data stored at this address
• data from RAM is copied to MDR
• PC is incremented to next instruction’s address

Question 15

Explain the fetch-execute cycle’s decode section

Answer 15

• MDR contains data or instruction thta was in the address
• this is copied to the CU which decodes the instruction

Question 16

Explain the fetch-execute cycle’s execute section

Answer 16

• the instruction is executed, which could mean a number of things:
• ALU performs a calculation, accumulator used, incrementing PC

Question 17

CPU function and purpose

Answer 17

• CPU = central processing unit
• a collection of billions of electronic switches that fetch decode and execute instructions
• purpose =process data and control rest of computer system
• works at high speeds governed by clock chip (vibrating crystal and every tick is one part of FDE cycle)

Question 18

Define register

Answer 18

A small memory location in CPU where data can be held temporarily and accessed quickly

Question 19

Define PC

Answer 19

• PC = program counter
• stores the address of the next instruction to be processed

Question 20

Define MAR

Answer 20

Memory address register - stores the address of the location in memory for data to be fetched from or sent to

Question 21

Define MDR

Answer 21

Memory data register - stores data fetched from or to be sent to memory

Question 22

Define ACC

Answer 22

Accumulator - stores results of the calculations carried out by ALU

Question 23

Name the 3 factors affecting CPU performance

Answer 23

• clock speed
• number of processor cores
• size of cache memory

Question 24

How does clock speed affect CPU performance?

Answer 24

• measured in GHz (x billion instructions per second)
• it’s number of cycles per second so higher clock speed means that more cycles per second
• CPU performance increases

Question 25

How does size of cache memory affect CPU performance?

Answer 25

• the more data stored in cache, the more efficient the process
• the larger the cache, the more likely it is that the required data is already copied to cache
• however, cache is very expensive so most laptops don’t have very much cache

Question 26

How does number of cores affect CPU performance?

Answer 26

• each core can execute instructions independently so multiple core processors can handle instructions simultaneously
• more cores means increased number of processes resulting in an increased of instructions executed per second

Question 27

What is an embedded system?

Answer 27

A computer system that has been designed for a dedicated function as a part of a bigger system

Question 28

Name 4 characteristics of embedded systems

Answer 28

Since they only have to carry out a single task or a limited set of tasks, they can be:
- cheap
- robust
- small
- low-power

Question 29

Explain why embedded systems are cheap and reliable

Answer 29

Lack of complexity in hardware and dedicated nature of software makes device more reliable and cost effective

Question 30

Explain why embedded systems use low power

Answer 30

They are low in power consumption so that they can operate effectively from a small power source

Question 31

Explain why embedded systems are small

Answer 31

Small in size so that they can fit into portable devices

Question 32

Explain why embedded systems are rugged

Answer 32

So that they can operate in hard environments such as car engines

Question 33

Explain why embedded systems are cost effective and cheap

Answer 33

Low cost makes them suitable for use in low-cost, mass-produced devices such as microwave ovens

Question 34

Explain why embedded systems have dedicated software

Answer 34

Dedicated software to complete a single task or limited range of tasks

Question 35

Examples of embedded systems

Answer 35

• washing machine
• car engine management systems
• home security systems
• card scanners
• microwave ovens