Primary And Secondary Storage Revision v2

​Embedded systems

Learning intention

Be able to describe what an embedded systems is and give some examples

Memory

Unit 1 Systems architecture

Embedded systems

• Do these devices have inputs, processes and

outputs?

• Could they be classed as computers?

• Why or why not?

Memory

Unit 1 Systems architecture

Embedded computers

• An embedded computer is a single microprocessor

that includes RAM, ROM and a CPU

• An embedded computer is frequently used to control a device

using simple inputs

​An embedded system is a computer built into a piece of equipment that performs a specific set of functions in that equipment

Activity 3

• Q+A

• 1) Produce a list of embedded systems found around the home

• Discuss the purpose of these with your partner

2) Produce a list embedded systems in a car. What is the ECU? Are
there any other embedded systems?

What sort of things could go wrong with embedded systems in cars?
What sort of problems might this cause?

2)​White

board

Memory

Unit 1 Systems architecture

Car embedded systems

• Some examples of embedded systems in

cars include:

• Cruise control

• Engine cooling fan

• Interior fans and temperature

• Interior lighting

• Rear cameras and remote parking

• Infotainment systems (entertainment / information / satnav)

• Engine control unit (ECU)

Objectives

• Explain the need for primary storage

• Describe the difference between RAM and ROM

• Describe the purpose of RAM and ROM in a

computer system

• Explain the need for virtual memory

Memory

Unit 1 Systems architecture

Starter

• What are four/five types of

memory that are used
in computers systems?

Memory

Unit 1 Systems architecture

Starter

• From previous lessons:

• CPU registers

• Cache

• This lesson:

• RAM

• ROM

• Virtual memory

Memory

Unit 1 Systems architecture

Types of primary storage

• There are many types of memory used in computers

• The two types used as primary storage are:

• RAM (Random Access Memory)

• ROM (Read Only Memory)

RAM

ROM

Memory

Unit 1 Systems architecture

What is RAM? What is used
for?

​Ask a student

Memory

Unit 1 Systems architecture

Operating system

• The computer first loads the operating

system from your hard drive into RAM

Operating

system

RAM

Memory

Unit 1 Systems architecture

Programs and data

• When applications or programs are

loaded, they are copied into RAM from
the hard drive

• Documents and files (data) that are used with

those programs are also opened by copying
them into RAM

• RAM starts to fill up as all these

programs, documents and files are copied

RAM

Operating

system

Word

Excel

Clipboard

Letter.docx

Memory

Unit 1 Systems architecture

RAM

• RAM is often referred to as:

• main memory, primary memory, primary storage

• It can be read from and written to

• Access to RAM is much faster than a hard drive

• The name Random Access Memory comes from the ability of

the CPU to access any part of the memory in the same
amount of time

• At any one time it will normally store:

•

The operating system (or part currently in use)

•

The software currently in use

•

The data which the software is using

Memory

Unit 1 Systems architecture

RAM

• The computer stores running programs and data in

RAM when your computer is turned on

• When your computer is turned off, data store in RAM

is lost

• RAM is volatile as it loses data if

the power is off

Open Ended

What is ROM and what is it used for?

Memory

Unit 1 Systems architecture

What is ROM? What is used
for?

​Ask a student

Open Ended

What is RAM and what is it used for?

Memory

Unit 1 Systems architecture

Read-only memory (ROM)

• Some data needs to be permanently held in primary

storage, even when a computer has no power

• Read-only memory (ROM) is used to store this data

• Data is read from ROM, but cannot be written to it

• It is non-volatile as the data isn’t lost if the power is off

• What is stored

in ROM on a
modern computer?

Memory

Unit 1 Systems architecture

ROM

• ROM is used in modern computers to store:

• The initial program that is run when the computer is turned on

• This is known as the bootstrap

• It tells the computer where it will find the operating system on

the hard drive

• It also stores the Basic Input/Output System (BIOS)

• The BIOS can run without a hard drive or other secondary

storage being present

• It controls basic technical configuration of the computer such

as the processor speed and system time

Memory

Unit 1 Systems architecture

What is primary storage and what is used for?

​Ask a student

Open Ended

What is primary storage and what is used for?

Memory

Unit 1 Systems architecture

Primary Storage – RAM + ROM

The CPU needs access to instructions as part of fetch
decode and execute.

It needs fast access.

Only RAM (and cache) + ROM provide storage
such memory storage for running programs and
their instructions (code).

Memory

Unit 1 Systems architecture

Picture round memory

• D:\aICT\Year10\_____________________________

_______________________J277\J277
GCSE\PGOnline\PGOnline\OCR J277 Unit 1
Systems
architecture\Yr10Revision\MemoryPictureRoundWith
Images.docx

Memory

Unit 1 Systems architecture

Question

RAM

ROM

What does it

stand for?

What is often
stored in it?

What

happens to its

contents

when you turn

the power

off?

Can you read

from and

write data to

it?

​Whiteboard

Memory

Unit 1 Systems architecture

Question

RAM

ROM

What does it

stand for?
Random Access Memory

Read Only Memory

What is often
stored in it?

Operating system
Running programs

Data currently being used

Computing bootup

instructions (Bootstrap loader)

/BIOS

What

happens to its

contents

when you turn
the power off?

They are lost

This type of memory is

volatile

They are retained

This type of memory is non-

volatile

Can you read
from and write

data to it?

Read and Write

Read Only. The contents are
written to it permanently at
the point of manufacture.
(Modern ROMs will allow
updates to occasionally be

stored on them, but these are

still thought of as ROMs as
this is a very slow process

that is rarely used)

MARKS

2

2

2

2

Memory

Unit 1 Systems architecture

What does the operating
system do when you try to
open a program/new tab of a
browser but all the RAM is
currently filled with running
programs and their data?

​Ask a student

Memory

Unit 1 Systems architecture

RAM

• When the computer is first turned on,

no data is stored in RAM

RAM

Empty

Memory

Unit 1 Systems architecture

Operating system

• The computer first loads the operating

system from your hard drive into RAM

Operating

system

RAM

Memory

Unit 1 Systems architecture

Programs and data

• When applications or programs are

loaded, they are copied into RAM from
the hard drive

• Documents and files (data) that are used with

those programs are also opened by copying
them into RAM

• RAM starts to fill up as all these

programs, documents and files are copied

RAM

Operating

system

Word

Excel

Clipboard

Letter.docx

Memory

Unit 1 Systems architecture

Running out of space

• You now want to open a

browser to search the Internet

• The browser software needs

more memory than you have
free in RAM

• What do you think happens?

RAM

Operating

system

Word

Excel

Clipboard

Documents

in use

Browser

Memory

Unit 1 Systems architecture

Virtual memory

• Virtual memory is part of the

hard drive used as an extension
to RAM

•What are the advantages and
disadvantages of using part of the
hard disk in this way?

RAM

Hard Disk

Browser

Operating

system

Word

Excel

Clipboard

Documents

in use

A ​Currenlty unused program's instruction and data are copied from RAM to secondary storage (the hard drive).

This frees up memory for new program (e.g. Browser)

Memory

Unit 1 Systems architecture

Virtual memory

• Advantages

• Uses cheap secondary storage on the hard drive

• Prevents error messages saying ‘out of memory’ – the

programs and files will still open

• Disadvantages

• Accessing virtual memory is very slow

• To access data, the existing data in RAM needs to be copied

to the virtual memory, then data in virtual memory needs to be
copied to RAM

Open Ended

What does the operating system do when you try to open a program/new tab of a browser but all the RAM is currently filled with running programs and their data?

Memory

Unit 1 Systems architecture

What happens when RAM
completely fills up?

Memory

Unit 1 Systems architecture

Memory speed

• The speed that data can be accessed changes

through the different components in a computer

• The slower components are far cheaper for each byte of

data stored

Memory

Unit 1 Systems architecture

Plenary

• In pairs test each other on the following:

1.

What does RAM stand for?

2.

What does ROM stand for?

3.

Name one difference between RAM and ROM

4.

How much RAM is typically available in a modern
personal computer?

5.

Why is virtual memory much slower than RAM?

Memory

Unit 1 Systems architecture

Plenary

• RAM stands for Random Access Memory

• ROM stands for Read Only Memory

• RAM can be written to, ROM can’t

ROM is non-volatile, RAM is volatile

• Typically, a modern personal computer will have 8-32 GB of

RAM available

Objectives

• Discuss the need for secondary storage including

optical, magnetic and solid state storage

• Evaluate suitable storage devices and media for a

given application using the following characteristics:

• Capacity

• Speed

• Portability

• Durability

• Reliability

• Cost

Secondary storage

Unit 1 Systems architecture

What are the three secondary storage technologies?

​Ask a student

Open Ended

What are the three secondary storage technologies?

​Picture round on Magnetic Storage

Secondary storage

Unit 1 Systems architecture

Picture rounds Secondary Storage

4 slides = Magnetic picture rounds

4 slides = Solid state + table of comparison

Omit if not enough time

4 slides = Optical

Secondary storage

Unit 1 Systems architecture

Magnetic disks

Basic features:

• Disk contains concentric

circles called tracks

• Each track is divided

into sectors

• Disk heads mounted on

mechanical arms read
and write the data

• A disk with a solid

platter is a ‘hard’ disk

• Soft plastic disks are

known as ‘floppy’ disks

Secondary storage

Unit 1 Systems architecture

Hard disks

• Parts of a hard disk

Drive read/write head
reads data on the drive

Magnetic platter
contains data

Drive spindle rotates

Actuator
moves the
read/write arm

Secondary storage

Unit 1 Systems architecture

Magnetic storage: hard disks

• Fixed magnetic hard disks are still used in many PCs and laptops

• They have a very large storage capacity, up to 6TB or more

• They are a very cheap form of storage compared to solid state drives

• Portable hard disks can

be connected to a
computer via a USB port

• They are used for

backing up or
transporting data

Secondary storage

Unit 1 Systems architecture

Magnetic storage

• Advantages:

• Cheap, large storage capacities, relatively fast write speed

• Disadvantages:

• Lots of mechanical parts, durability an issue, sealed unit due to disk head and platter

precision and not very portable

• Uses:

• Personal computers, storage of large quantities of data

• Capacity:

• 500GB - 12TB or greater

Secondary storage

Unit 1 Systems architecture

Solid State Drives (SSD)

• Basic features:

• Solid-state disks use

non-volatile flash memory to
store information

• Very fast read/write speeds as

it doesn’t need to wait for a
disk to spin to the correct
location and an arm to move

• No mechanical or moving

parts meaning these disks are
very durable

Secondary storage

Unit 1 Systems architecture

Advantages /disadvantages
of SSDs

• Advantages:

• Highly durable, no moving parts, very fast read/write speeds,

no noisy fan or drive arm, faster start up times

• Disadvantages:

• More expensive than magnetic hard disks, similar storage

capacity as magnetic disks

• Uses:

• Higher end computers
• Laptops
• Smartphones and tablets

• Capacity:

• 100GB – 16TB

Secondary storage

Unit 1 Systems architecture

Flash memory

• Solid State

• Low cost, portable, no moving parts, durable

• This makes them ideal for a range of offline devices:

• Cameras

• Mobile phones

• USB memory sticks

Secondary storage

Unit 1 Systems architecture

Capacity

Speed

Cost

Cost per GB

HDD

2 TB+

1 GB/s

£35

3.5p

SSD

480 GB+
535
MB/s
£55

11.5p

Blu-ray

25 GB (pack of 50)

36 MB/s
(8x
speed)

£0.56 per
disk
2.2p

SD card

128 GB
100
MB/s
£16

12.5p

Approximate

Secondary storage

Unit 1 Systems architecture

Optical storage

• Basic features:

• Data is stored as pits and

lands burnt or pressed into a
spiral track circulating
outwards from the centre

• A laser beam passes over the

pits and lands the level of
reflection is measured

• From this signal, 0s and 1s

can be derived

Secondary storage

Unit 1 Systems architecture

How CDs work

Secondary storage

Unit 1 Systems architecture

Optical storage

• Advantages:

• Cheap, very easily portable, takes up little space physically

• Disadvantages:

• Less storage capacity compared to other types
• Easily damaged / scratched, requires a CD reader
• Slow write speeds

• Uses:

• Songs, videos and other multi-media storage, backup and archiving of data

• Capacity:

• CD-ROM – up to 720 MB
• DVD – up to 8.4 GB (dual layered disk)
• Blu-Ray – up to 50 GB (dual layered disk)

​•Characteristics of storage devices

•Capacity: Magnetic High, Solid state varies, Single DVD small

•Speed: Sold state Hard drive fast, Magnetic medium, Optical Slow

•Portability: Optical/DVD very portable, SSHD small portable, Magnetic hard drive less portable

•Durability: will the device break if dropped? How well does it work with extreme temperatures or magnetic fields? Magnetic NOT durable, SSHD more durable (no moving parts), DVD can be scratched easily(not durable)

•Cost: what is the cost of a device? Optical/DVD cheapest, Magnetic next cheapest, Solid state (flash or Flash Memory stick) most expensive

Secondary storage

Unit 1 Systems architecture

Three secondary storage technologies

• Magnetic: Mechanical parts move over the disks

surface to read and write data magnetically, or a
drive head reads a magnetic tape

• Optical: Lasers read and write data using light

• Solid State: Data is recorded onto solid memory

chips without any moving parts

Secondary storage

Unit 1 Systems architecture

Worksheet 4

• Complete

• Task 1 on

• Worksheet 4

Secondary storage

Unit 1 Systems architecture

Storage device

Magnetic

Optical
Solid
state

Hard disk drive



Blu-ray



CD ROM



USB flash drive



DVD RAM



SSD hard drive



SD card



Floppy disk drive



Backup tape drive 

Secondary storage

Unit 1 Systems architecture

How does magnetic hard drive work?

How does a Solid state hard drive work?

How does a Optical reader work?

Open Ended

How does a Solid state hard drive work?

Open Ended

How does magnetic hard drive work?

Open Ended

How does an optical drive work?

Secondary storage

Unit 1 Systems architecture

Storage methods

• Magnetic: Mechanical parts move over the disks

surface to read and write data magnetically, or a
drive head reads a magnetic tape

• Optical: Lasers read and write data using light

• Solid State: Data is recorded onto solid memory

chips without any moving parts

Secondary storage

Unit 1 Systems architecture

Storage types

• Primary storage

• RAM and ROM

• Secondary storage

• Hard Disk Drive (HDD)

• Solid State Drive (SSD)

• Offline secondary storage

• Compact Disc (CD), Digital Versatile Disc (DVD) or BluRay

• Flash memory, SD cards

• Removable HDD or SSD

• Magnetic tape

Secondary storage

Unit 1 Systems architecture

Secondary storage

• Secondary storage is not directly

accessible by the CPU Meaning there are special

• Reading/writing methods different to

RAM/cache/Main memory

• It is non-volatile, meaning

it will keep data even if there
is no power

• Secondary storage devices

may be internal or external
to the computer

• What is secondary storage

used for?

Open Ended

What different things are secondary storage devices used for?

Secondary storage

Unit 1 Systems architecture

Uses of secondary storage

• It has many different uses – for example:

• Programs and data are stored on hard drive

• Blu-rays may be used to distribute films

• Memory sticks may be used to transport data from one place

to another

• Magnetic tape or external hard drives may be used for backup

• SD cards can be used for additional storage on cameras

and smartphones – this is used for music, video and photos

Secondary storage

Unit 1 Systems architecture

Picture rounds Secondary
Storage

4 slides = Magnetic picture rounds

4 slides = Solid state + table of comparison

Omit if not enough time

4 slides = Optical

Secondary storage

Unit 1 Systems architecture

Magnetic storage

• Advantages:

• Cheap, large storage capacities, relatively fast write speed

• Disadvantages:

• Lots of mechanical parts, durability an issue, sealed unit due

to disk head and platter precision and not very portable

• Uses:

• Personal computers, storage of large quantities of data

• Capacity:

• 500GB - 12TB or greater

Secondary storage

Unit 1 Systems architecture

Advantages /disadvantages
of SSDs

• Advantages:

• Highly durable, no moving parts, very fast read/write speeds,

no noisy fan or drive arm, faster start up times

• Disadvantages:

• More expensive than magnetic hard disks, similar storage

capacity as magnetic disks

• Uses:

• Higher end computers
• Laptops
• Smartphones and tablets

• Capacity:

• 100GB – 16TB

​•Characteristics of storage devices

•Capacity: How much data can be stored – e.g. 700 MB, 50 GB or 2 TB

•Speed: The rate (usually in MB/s) at which data can be read or written

•Portability: how easy it is to carry – is the device small?

•Durability: will the device break if dropped? How well does it work with extreme temperatures or magnetic fields?

•Cost: what is the cost of a device? How much is it to store
1 MB of data

Secondary storage

Unit 1 Systems architecture

Storage characteristics

• Characteristics of storage devices

• Capacity: Magnetic High, Solid state varies, Single DVD

small

• Speed: Sold state Hard drive fast, Magnetic medium, Optical

Slow

• Portability: Optical/DVD very portable, SSHD small portable,

Magnetic hard drive less portable

• Durability: will the device break if dropped? How well does it

work with extreme temperatures or magnetic fields? Magnetic
NOT durable, SSHD more durable (no moving parts), DVD
can be scratched easily(not durable)

• Cost: what is the cost of a device? Optical/DVD cheapest,

Magnetic next cheapest, Solid state (flash or Flash Memory
stick) most expensive

Secondary storage

Unit 1 Systems architecture

Calculating data capacity

• Knowing the capacity required will enable us to

make an informed decision as to which device to use

• If we wish to store 5000 photos and each photo has

a file size of 10 MB, we need a total of 50 GB

• Which storage devices are suitable for this amount of data?

• Which storage device would be suitable for storing this data

on a smartphone?

Secondary storage

Unit 1 Systems architecture

Calculating data capacity

• Knowing the capacity required will enable us to

make an informed decision as to which device to use

• If we wish to store 5000 photos and each photo has

a file size of 10 MB, we need a total of 50 GB

• Which storage devices are suitable for this amount of data?

• Hard Drive (Magnestic)

• Large Flash memory stick

• Optical Disk.

• SSHD

• Which storage device would be suitable for storing this data

on a smartphone?

• Flash Memory Card / SSHD

Secondary storage

Unit 1 Systems architecture

Plenary

• In pairs, give answers to the following:

• 5 examples of storage devices

• 4 other characteristics of storage devices other than cost

• 3 technologies that storage devices use

• 2 words that describe

data that is or isn’t
lost when power is
turned off

• 1 word that means

1000 Gigabytes

Open Ended

Give 5 examples of storage devices

Open Ended

4 other characteristics of storage devices other than cost

Open Ended

Give 3 technologies that storage devices use

Open Ended

Give 2 words that describe data that is or isn’t lost when power is turned off

Open Ended

Give 1 word that describes 1000 Gigabytes

Secondary storage

Unit 1 Systems architecture

Plenary

• Examples of storage devices:

• Hard disk drive, floppy disk drive, tape drive, CD drive, DVD

drive, Blu-ray drive, USB flash drive, SSD drive, SD card

• Characteristics of storage devices:

• Capacity, speed, portability, durability, reliability (and cost)

• Technologies used in storage devices:

• Magnetic, optical, solid state

• Volatile – data is lost; non-volatile – data is not lost

• 1 Terabyte (TB) = 1000 Gigabytes

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Secondary storage

Unit 1 Systems architecture

Memory

Unit 1 Systems architecture

Plenary

1. Name three common factors which affect the

performance of a CPU

2. What do each of these factors mean?

3. What is an embedded system?

4. Name three examples of an embedded system

Registers…super fast memory
stores that are part of the CPU.

• Memory Address Register(M.A.R.)…holds the

address of the next item in memory to be accessed
(read or write)

• Memory Data Register(M.D.R)…2 way data “buffer”

that holds data either read from or to be written to
main memory (RAM or cache)

• Program Counter(P.C.)…holds the memory address

of the next instruction

• Accumulator(ACU)…holds the value of any current

arithmetic work

Memory

Unit 1 Systems architecture

Plenary

1. Name three common factors which affect the

performance of a CPU

2. What do each of these factors mean?

3. What is an embedded system?

4. Name three examples of an embedded system

Memory

Unit 1 Systems architecture

Plenary

1. Clock speed, number of cores, cache size

2. Clock speed – the number of fetch-execute cycles

per second; number of cores – the number of
processing units on each CPU; cache – memory
that is faster than RAM and slower than the
registers, normally located on the CPU

3. A computer system that is used to control

mechanical or electrical systems

4. Satnav, microwave, dishwasher, burglar alarm,

washing machine, digital watch…

Memory

Unit 1 Systems architecture

Starter - recap

• Name at least five components inside a CPU

• What is the purpose of each component?

Memory

Unit 1 Systems architecture

Starter

• Components in a CPU

• Control unit (CU) – decodes the instructions; controls the

timing of operations in the CPU

• Arithmetic Logic Unit (ALU) – performs arithmetic and

logic operations

• Registers – including PC (program counter) for the next

instruction; MAR (memory address register) for the memory
location of data to be fetched; MDR (memory data register)
data retrieved from RAM; Accumulator (ACC) stores the
results from the ALU