Unit 3 CPU Architecture

Objectives

• Understand the role of the CPU and the

fetch-execute cycle

• Understand the following registers in the Von

Neumann architecture:

• MAR (Memory Address Register)

• MDR (Memory Data Register)

• CIR (Current Instruction Register) • Program Counter (PC)

• Accumulator (ACC)

• Understand common CPU components including:

• ALU (Arithmetic Logic Unit)

• CU (Control Unit)

• Registers

CPU architecture

Unit 3 Computer architecture and storage

Starter

• A laptop and smartphone are both examples of

computer systems

• What are the input and output devices for these computer

systems?

• What component carries

out the processing of
the instructions?

CPU architecture

Unit 3 Computer architecture and storage

Starter

• Input devices:

• Laptop: keyboard, buttons, trackpad, microphone

• Smartphone: microphone, buttons, GPS sensor, gyroscopic

sensor, touch part of the touchscreen

• Output devices:

• Laptop and smartphone: speakers, display

• Processing:

• CPU (Central Processing Unit)

CPU architecture

Unit 3 Computer architecture and storage

The main components
of a computer

MAIN MEMORY

SECONDARY

STORAGE

CENTRAL PROCESSING

UNIT (CPU)

INPUT

DEVICES

OUTPUT
DEVICES

CPU architecture

Unit 3 Computer architecture and storage

What is this?

Fill in the Blank

What is this?

CPU architecture

Unit 3 Computer architecture and storage

The CPU

CPU architecture

Unit 3 Computer architecture and storage

Central Processing Unit (CPU)

• The Central Processing Unit or CPU is arguably the

most important component of a computer

• What does it do?

• What organ in the human body

is it often compared to?

• What are the similarities it has

to this organ?

CPU architecture

Unit 3 Computer architecture and storage

The purpose of the CPU

• The CPU processes instructions

• When you run a program, it is the

CPU which processes the
instructions and data that are input

• The results are then output

• It is often thought of as being

the ‘brains’ of the computer

• The way that a brain works is

very different to a CPU

• A CPU simply runs one

simple instruction at a time, but billions
of instructions are carried out each second

CPU architecture

Unit 3 Computer architecture and storage

Stored program concept

• Before about 1943, early computers stored the data

to be worked on in memory. The program was not
stored

• Instructions were input one at a time using switches, or

read in punch cards and executed one at a time

• In 1943-44, mathematician von Neumann and his

colleagues had the idea of storing both the program
instructions as well as the data in memory

• The stored-program computer was born! Another

name is the Von Neumann Architecture

CPU architecture

Unit 3 Computer architecture and storage

Von Neumann architecture

• Both program instructions and the data the programs are

using are both stored in the same memory

• The CPU accesses both instructions and data from the

same RAM

• Each instruction or data item is fetched from memory, decoded and

then executed with any new data created being placed back into
memory.

Multiple Choice

What is the Von Neumann architecture?

• A. Storing only program instructions in memory

• B. Storing only data in memory

• C. Storing both program instructions and data in the same memory

• D. Storing program instructions separately from data

Multiple Choice

How does a CPU execute instructions in the Von Neumann architecture?

• A. Instructions and data are stored in separate memories

• B. Instructions are executed first, followed by the execution of data

• C. Both instructions and data are fetched from the same memory, decoded, and then executed

• D. Instructions and data are fetched simultaneously

Multiple Choice

Which of the following best describes the role of the CPU ?

• A. Executing complex instructions simultaneously/at the same time

• B. Running multiple instructions at once

• C. Running one simple instruction at a time, but billions of instructions per second

• D. Storing program instructions and data in separate memories

CPU architecture

Unit 3 Computer architecture and storage

Components of the CPU

• The CPU has two major components

called the

• Control Unit

• Arithmetic-Logic Unit (ALU)

• There are also special purpose

registers that are used to carry out
these operations

• A register is a very fast memory location in

the CPU itself

• Cache memory is located on the CPU –

it is slower to access than registers but faster
than RAM

CPU architecture

Unit 3 Computer architecture and storage

Special purpose registers

• Program Counter (PC)

holds the address of the next instruction to be fetched then
executed

• Memory Address Register (MAR)

holds the memory address of the current instruction being fetched
from memory

• Memory Data Register (MDR)

holds the actual instruction or data that has been fetched from
memory

• Current Instruction Register (CIR)

holds the instruction currently being executed or decoded

• Accumulator (ACC)

holds the result of an instruction/operation that is being executed

CPU architecture

Unit 3 Computer architecture and storage

Control Unit

• The control unit coordinates and

controls the function and operation of the
CPU

• This includes the FE cycle (fetch, decode and

execute instructions)

• It receives signals from the system clock

• It directs the timing and control of other

parts of the CPU, much like the conductor
of an orchestra

CPU architecture

Unit 3 Computer architecture and storage

The Arithmetic Logic Unit

• The ALU or Arithmetic Logic Unit is where the actual

operations are done

• This includes basic arithmetic as well as logical operations,

such as AND, OR and NOT

Main

Memory
X = 3
Y = 5

Accumulator

8
ADD X, Y

ALU

CPU architecture

Unit 3 Computer architecture and storage

Worksheet 1

• Complete Task 1

CPU architecture

Unit 3 Computer architecture and storage

Fetch – Decode – Execute

• The CPU operates by repeating

three operations:
•

FETCH – causes the next
instruction and any data
involved to be fetched from
main memory

•

DECODE – analyses the
instruction

•

EXECUTE – the instruction
is computed

• This process is then repeated…

CPU architecture

Unit 3 Computer architecture and storage

CPU architecture

Unit 3 Computer architecture and storage

Program Counter (PC)

• The Program Counter holds

the address of the next
instruction to be fetched
and then executed

• The Program Counter is

incremented (increased by 1)
as soon as that instruction has
been fetched

1

2

3

4

5LDA 10

6ADD 11

7STO 12

8

9

10

50

11

17

12

Program
Counter

5

CPU architecture

Unit 3 Computer architecture and storage

CPU architecture

Unit 3 Computer architecture and storage

Accumulator

• The accumulator (ACC) is

where arithmetic and logic
results are temporarily
stored, much like the M+
function on
a calculator

CPU architecture

Unit 3 Computer architecture and storage

CPU architecture

Unit 3 Computer architecture and storage

MAR and MDR

• In the FETCH stage of the F-E cycle

• the address of the instruction to be executed is copied from the

Program Counter (PC) to the Memory Address
Register (MAR), and sent to the memory via the address bus

• The instruction (or data) at that address is fetched from memory

and copied to the Memory Data Register (MDR) via the data bus

• The Control Unit decodes the instruction and decides if

data needs to be fetched

• If so, the MAR is then used to hold the address of the

data to be used in the instruction

• The data is fetched and copied to the MDR

CPU architecture

Unit 3 Computer architecture and storage

Working together

MAR (Memory Address Register)

MDR (Memory Data Register)

The two work together; The MAR knows where to look
for data in RAM, the MDR keeps hold of that data until
it’s ready to be used by the CPU

MDR

(Memory

Data

Register)

MAR

(Memory
Address
Register)

CPU architecture

Unit 3 Computer architecture and storage

CPU architecture

Unit 3 Computer architecture and storage

Current instruction register (CIR)

• The current instruction register holds the

instruction whilst it is being decoded, then executed

• It is also known as the instruction register (IR), but the

name current instruction register gives you a clue that it is the
instruction that is ‘currently’ being decoded / executed that it
holds

• Once the instruction is loaded from memory it is stored in the

current instruction register (CIR)

• Once the instruction is in the CIR it is decoded

• If data is needed that is stored in memory it will be fetched

CPU architecture

Unit 3 Computer architecture and storage

Processor architecture

• What does each acronym stand for?

• What does each part do?

CPU architecture

Unit 3 Computer architecture and storage

1.

The Control Unit controls and coordinates

all the activities in the CPU

2.

The Program Counter holds the address

of the next instruction to be executed

3. The Address in the PC is passed to MAR and PC is incremented by one each time

the instruction is fetched. The Address bus is used to fetch the instruction from
RAM

4. The instruction is then copied from memory into the MDR using the data bus.

5. The instruction is passed to the CIR where the control Unit (6) decodes

it.(Determining the Opcode and Operand)

Opcode eg ADD, SUB, LDA, STO Operand eg #10(value) or 10 – (Address 10)

7. Depending on the Instruction at 6 above, at the Execute Stage, the instruction may

be operated upon ALU or value stored temporarily in the Accumulator. The ALU
can also make use of the Accumulator as its temporary storage.(9)

THE FDE CYCLE IN DETAIL

CPU architecture

Unit 3 Computer architecture and storage

Processor architecture

ACC:
Accumulator –
Temporarily stores
arithmetic results

ALU:
Arithmetic Logic
Unit – performs
calculations and
logic expressions

MDR:
Memory data register – Stores the
data to be sent/received from memory

RAM:
Random Access
Memory

PC:
Program Counter – points
to the next instruction

MAR:
Memory Address Register – stores the
address of the instruction to be executed

CIR:
Stores the current
instruction to be
decoded and
executed

CPU architecture

Unit 3 Computer architecture and storage

Example – Step 1

• PC points to next instruction in location 5

• Address 5 is passed to MAR and PC is

incremented. It now holds 6

• Instruction at Address 5 is copied from

memory to MDR

• Instruction passes to the CIR where it is

decoded by control unit. It knows LDA
means Load what is in address 10

• Address 10 passed to the MAR

• The value in location 10, i.e. 8, is passed

from main memory to the MDR

• 8 is loaded into the accumulator (ACC)

1

2

3

4

5

LDA 10

6

ADD #4

7

STO 11

8

9

10

8

11

12

Program
Counter

5

Acc
8

(Add 8 + 4)

CPU architecture

Unit 3 Computer architecture and storage

Example – Step 2

• PC now points to next instruction in

location 6

• Address 6 is passed to the MAR and

the PC is incremented

• Instruction at Address 6 passed to MDR

• The instruction is passed to the CIR and

then decoded

• No more data from memory is needed

• 4 is added to 8 in the ALU and the result

is stored in the accumulator (ACC)

1

2

3

4

5

LDA 10

6

ADD #4

7

STO 11

8

9

10

8

11

12

Program
Counter

6

Acc
12

CPU architecture

Unit 3 Computer architecture and storage

Example – Step 3

• PC points to the next instruction in

location 7

• Address 7 is passed to the MAR and the

PC is incremented

• Instruction at Address 7 passed to MDR

• The instruction is passed to the CIR to

be decoded

• The instruction is executed causing the

value 12 to be transferred from the
accumulator into memory location 11

1

2

3

4

5

LDA 10

6

ADD #4

7

STO 11

8

9

10

8

11

12

12

Program
Counter

7

Acc
12

CPU architecture

Unit 3 Computer architecture and storage

Worksheet 1

• Complete Task 2

Multiple Choice

Which component of the CPU is responsible for holding the result of an instruction or operation that is currently being executed?

• A. Control Unit

• B. Arithmetic-Logic Unit (ALU)

• C. Memory Data Register (MDR)

• D. Accumulator (ACC)

Multiple Choice

What is the function of the Memory Address Register (MAR) in the CPU?

• A. Holds the result of an instruction or operation

• B. Holds the memory address of the current instruction being fetched from memory

• C. Holds the address of the next instruction to be fetched then executed

• D. Holds the actual instruction or data fetched from memory

Multiple Choice

Where is cache memory located in the CPU, and how does its speed compare to RAM?

• A. Located on the motherboard; slower than RAM

• B. Located on the CPU; faster than RAM

• C. Located on the CPU; slower than RAM

• D. Located on the motherboard; faster than RAM

Multiple Choice

Which special purpose register in the CPU holds the instruction currently being executed or decoded?

• A. Program Counter (PC)

• B. Memory Address Register (MAR)

• C. Current Instruction Register (CIR)

• D. Accumulator (ACC)

Multiple Choice

What is the primary role of the Program Counter (PC) in the CPU?

• A. Holds the result of an instruction or operation

• B. Holds the memory address of the current instruction being fetched from memory

• C. Holds the address of the next instruction to be fetched then executed

• D. Holds the actual instruction or data fetched from memory

CPU architecture

Unit 3 Computer architecture and storage

Plenary

• In pairs, answer the following:

• What is the purpose of the CPU?

• What are two major components

of the CPU, and what is the
purpose of each?

• What is a register?

• Name four special

registers in the CPU

CPU architecture

Unit 3 Computer architecture and storage

Plenary

• What is the purpose of the CPU?

• To fetch and execute instructions stored in memory

• What are two major components of the CPU, and

what is the purpose of each?

• The ALU, which carries out arithmetic and logic instructions

• The Control Unit, which coordinates the CPU activities

• What is a register?

• A special fast memory location in the CPU

• Name four special registers in the CPU

• PC, MAR, MDR, CIR, Accumulator (ACC)

CPU architecture

Unit 3 Computer architecture and storage

Processor architecture

ACC:
Accumulator –
Temporarily stores
arithmetic results

ALU:
Arithmetic Logic
Unit – performs
calculations and
logic expressions

MDR:
Memory data register – Stores the
data to be sent/received from memory

RAM:
Random Access
Memory

PC:
Program Counter – points
to the next instruction

MAR:
Memory Address Register – stores the
address of the instruction to be executed

CIR:
Stores the current
instruction to be
decoded and
executed

CPU architecture

Unit 3 Computer architecture and storage

Plenary

• In pairs, answer the following:

• What is the purpose of the CPU?

• What are two major components

of the CPU, and what is the
purpose of each?

• What is a register?

• Name four special

registers in the CPU

CPU architecture

Unit 3 Computer architecture and storage

CPU architecture

Unit 3 Computer architecture and storage

​Recap Questions - 100%= 1 Merit

CPU architecture

Unit 3 Computer architecture and storage

​

CPU architecture

Unit 3 Computer architecture and storage

​

CPU architecture

Unit 3 Computer architecture and storage

​

CPU architecture

Unit 3 Computer architecture and storage

​

CPU architecture

Unit 3 Computer architecture and storage

​

CPU architecture

Unit 3 Computer architecture and storage

​

CPU architecture

Unit 3 Computer architecture and storage

CPU architecture

Unit 3 Computer architecture and storage

CPU architecture

Unit 3 Computer architecture and storage

​

Quiz link CPU Architecture

CPU architecture

Unit 3 Computer architecture and storage

Objectives

• Understand the following terms and how they affect

the performance of a CPU:

• Cores

• Cache

• Clock

• Understand the purpose of buses including:

• The address bus

• The data bus

• The control bus

CPU architecture

Unit 3 Computer architecture and storage

Starter - recap

• Name at least five components inside a CPU

• What is the purpose of each component?

CPU performance and buses

Unit 3 Computer architecture and storage

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; CIR (current instruction register) to
store the instruction currently being decoded or executed;
Accumulator (ACC) stores the results from the ALU

CPU architecture

Unit 3 Computer architecture and storage

What affects CPU performance?

• The following are three of the most common factors

which can affect a CPU’s performance

• Clock speed

• Processor cores

• Cache

• What is the purpose of each of these components?

• How can they affect the performance

of the CPU?

CPU architecture

Unit 3 Computer architecture and storage

Factors affecting CPU performance

Clock speed
Cache size

Number of cores

Cycles per second
measured in hertz (Hz)

The number of duplicate
processing units (cores)
placed in one CPU

Cache on the CPU

is faster than RAM but

slower than registers

CPU architecture

Unit 3 Computer architecture and storage

CPU

Control Unit

CPU

Control Unit

1. Clock speed

• The clock generates a signal that is used to synchronise

the operation of the processor and the movement of
data around other components of the computer

• Everything in a computer happens on the pulse of the internal clock

• Therefore, the faster the clock speed, the faster the

instructions are processed

Clock

Clock

Clock speed 1GHz

Clock speed 2GHz

1 Billion FDE cycles per second

2 Billion FDE cycles per second

Factors affecting CPU performance

CPU architecture

Unit 3 Computer architecture and storage

Processor Speed

• One cycle per second = 1 hertz (Hz) = 1 instruction

carried out each second

• 1 kilohertz (kHz) = 1000 cycles per second

• 1 Megahertz (MHz) = 1,000,000 cycles per second

• 1 Gigahertz (GHz) = 1,000,000,000 cycles per second

• How fast is your computer’s processor?

• Remember, a 1 GHz processor is performing one

billion cycles per second

CPU architecture

Unit 3 Computer architecture and storage

Check your device CPU speed

processor

Multiple Choice

What is the primary relationship between clock speed and CPU performance?

• A. Higher clock speed always results in faster CPU performance

• B. Lower clock speed always results in faster CPU performance

• C. Clock speed has no impact on CPU performance

• D. The relationship between clock speed and CPU performance depends on other factors

CPU architecture

Unit 3 Computer architecture and storage

2. Multi-core processors

• A dual-core processor has two processors in the

same integrated circuit, linked together

• A dual-core processor has the potential to perform two

instructions at the same time

• This allows twice as many instructions to be executed,

however, it doesn’t always perform at this rate as software
may not be able to take full advantage of both cores

• A quad-core processor has four linked processors

• Which processor would you prefer, a dual-core

1GHz, or a 3 GHz single core processor?

Factors affecting CPU performance

CPU architecture

Unit 3 Computer architecture and storage
Effect on speed

• A quad-core processor working on many different

tasks simultaneously, under ideal conditions can be
up to four times faster than a single-core processor

NOTE

• If the computer is running a single program,

it is not necessarily any faster, since the
program may have been designed to only
run on one core

• Therefore, its only in theory that multi cores

will guarantee multiple processes at the
same time.

Multiple Choice

How does a multi-core processor differ from a single-core processor in terms of potential performance?

• A. Multi-core processors are always slower than single-core processors

• B. Multi-core processors can perform multiple instructions simultaneously

• C. Single-core processors have higher clock speeds than multi-core processors

• D. Multi-core processors use less cache memory than single-core processors

CPU architecture

Unit 3 Computer architecture and storage

3. Cache memory

• Cache is a small amount of

very fast, expensive memory in
the CPU

• It can be accessed faster than

regular main memory (RAM)

• Why is this useful for

recently/frequently
used data?

CPU

Cache

Main Memory

Factors affecting CPU performance

When an instruction is fetched from main
memory, it is copied into cache so if it is needed
again soon after, it can be fetched quicker.

CPU architecture

Unit 3 Computer architecture and storage

Effect on speed of cache

• RAM is relatively slow memory to access and it is

further away from the processor than cache

• It takes longer to retrieve an instruction or data from RAM

than from cache

• Program instructions and data that are fetched are

stored in cache in case they are needed again soon

Example

If you have a ‘while’ loop in a program, for example, having all

the instructions in the loop in cache, speeds up execution

CPU architecture

Unit 3 Computer architecture and storage

Levels of cache memory

• There are different ‘levels’ of cache:

• Level 1 cacheis extremely fast but small (between 2-

256KB), located on the CPU. Each core will have its
own Level 1 cache

• Level 2 cacheis usually also given to each core. It is

very fast, but a little slower than Level 1 cache. The
typical size is 256KB-8MB

• Level 3 cache is the slowest type of cache, but still

faster than RAM. It is usually located on the CPU and
stores 4MB-50MB. The cache is shared between all the
cores on the processor

CPU architecture

Unit 3 Computer architecture and storage

Levels of cache memory

CPU architecture

Unit 3 Computer architecture and storage

The benefits of cache

• The data used most often by the CPU is held

in Level 1 cache so is available extremely
quickly

• In most systems, Level 1 cache is used about 50% of the

time, with Level 2 cache being accessed about 90% of the
time

• This greatly reduces the time that the CPU has to wait for

data from main memory

• The size of the Level 2 cache is a major factor

in determining the performance of the CPU

Multiple Choice

Which level of cache memory is typically the fastest but also the smallest in size?

• A. Level 1 cache

• B. Level 2 cache

• C. Level 3 cache

• D. Main memory (RAM)

CPU architecture

Unit 3 Computer architecture and storage

Which is (theoretically) faster?

1. A dual core processor running at 2.7GHz with 4MB of

shared cache memory

2. A quad core processor running at 1.5GHz with 8MB

of shared cache memory

3. A single core processor running at 3.2GHz with 2MB

of cache memory

4. A dual core processor running at 3.2GHz with 4MB of

shared cache memory

Calculate the maximum number of cycles per second in
each case and rank them in order of performance

Multiple Choice

Which CPU will run the fastest?

• 1

• 2

• 3

• 4

CPU architecture

Unit 3 Computer architecture and storage

Worksheet 2

• Complete Task 1 on Worksheet 2

CPU architecture

Unit 3 Computer architecture and storage

Buses

• When the CPU wishes to access a

particular main memory location, it
sends the address requested to
memory on/via the address bus

• The data in that location is then

returned to the CPU on the
data bus

• Control signals are sent along the

control bus

A bus is a set of parallel wires connecting two or
more components of the computer

CPU architecture

Unit 3 Computer architecture and storage

System bus

• The three buses that make up the system bus are:

1.

Address Bus: carries the address of the memory or device
controller to be read from or written to. This bus is unidirectional.

2.

Data Bus: carries data throughout the computer system. This bus is bidirectional.

3.

Control Bus: carries control signals necessary to complete
executing instructions in the CPU. This bus is bidirectional. There is a lot of data
flowing around the CPU, the Control bus ensures that the
right data is travelling to the right place at the right time.

CPU architecture

Unit 3 Computer architecture and storage

External buses

• The CPU is also

connected to the external
Input-output device
controllers by means of
the system bus

• Only one device can transmit

along a bus at any one time

• The address bus is one way

only, from the CPU

• What about the data bus?

I/O controllers are a series of microchips which help in the communication of data
between the CPU and the motherboard. The main purpose of this system is to help
in the interaction of peripheral devices with the control units (CU)

•Physical input and output devices are connected via the ports.
The CPU does not communicate directly with theI/O devices, but
rather the I/O controller.

•It translates signals from the device into the format required by
the processor.

Internal Components – Input / Output

Controllers

Multiple Choice

When the CPU wants to access a specific main memory location, what role does the address bus play in this process?

• A. It carries the data from the requested memory location to the CPU

• B. It carries control signals (e.g., read/write) to the memory

• C. It carries the address of the memory location to be accessed

• D. It carries control signals to the CPU

Multiple Choice

What is the primary function of the control bus in the system bus architecture?

• A. Carrying data throughout the computer system

• B. Transmitting data from external input-output devices

• C. Carrying control signals necessary to complete executing instructions in the CPU

• D. Carrying the address of the memory or device controller

Multiple Choice

How does the data bus contribute to the communication within a computer system?

• A. It carries control signals necessary for executing instructions

• B. It carries the address of the memory location to be accessed

• C. It carries data throughout the computer system

• D. It is only responsible for transmitting data from external input-output devices

CPU architecture

Unit 3 Computer architecture and storage

Buses – summary

• Explain this diagram:

‘M’ key pressed

CPU

Main memory

CPU architecture

Unit 3 Computer architecture and storage

Buses – summary

• Explain this diagram:

‘M’ key pressed

CPU

Main memory

Control Bus

Address Bus

Data Bus

1. Get ready to store the letter ‘M’ into Main Memory

3. Here is the data: “01011001”

2. Store it in the following memory address location

CPU architecture

Unit 3 Computer architecture and storage

Worksheet 2

• Complete Task 2 and Task 3 on Worksheet 2

CPU architecture

Unit 3 Computer architecture and storage

Plenary

1. Name three common factors

which affect the performance
of a CPU

2. Name three types of bus

that are used in
computer architecture

3. Other than the

accumulator (ACC),
name three registers in
a CPU

CPU performance and buses

Unit 3 Computer architecture and storage

Plenary

1. Clock speed, number of cores, cache size

2. Address bus, data bus and control bus

3. Three from:

PC (program counter), MAR (memory address
register), MDR (memory data register), CIR
(current instruction register)

Quiz on the factors the affect
CPU performance & buses

CPU architecture

Unit 3 Computer architecture and storage

Objectives

• Understand the purpose and use of an instruction set

for a CPU

• Understand what is meant by a microprocessor
• Describe the purpose and characteristics of an

embedded system

– Be able to identify devices which commonly use

embedded systems

Embedded systems and instruction sets

Unit 3 Computer architecture and storage

Starter
• CPUs fetch, decode and execute

instructions

• In a high level language, you may program an

instruction
such as

total <-- 0
FOR i <-- 1 TO 10 DO
total <-- total + i
ENDFOR

• What sort of instructions

does a CPU
actually use?

Embedded systems and instruction sets

Unit 3 Computer architecture and storage

Starter

• CPUs use very simple instructions known as

machine code or assembly language

• A high level instruction such as total <-- 0 may use an

instruction such as LOAD ACC, #0

• Complex / structured instructions are broken down

into simpler assembly code instructions

• For example,

FOR i <-- 1 TO 10 DO
may need several
instructions to move
data between RAM
and the Accumulator

CPU architecture

Unit 3 Computer architecture and storage

Instruction sets

• Instruction sets are all the possible

instructions that are able to be decoded and
executed by a CPU

• A particular CPU will have its own instruction set

• Programs written for one type of CPU won’t work

on another

• For example, a program written for an Intel Core i7

won’t work on an ARM processor contained in a
smartphone

CPU architecture

Unit 3 Computer architecture and storage

Operators and operands

• In ordinary Maths and programming we use the

words operator and operand

• An operator performs an operation (calculation) on the

operand(s)

• The operands are the values used

5

+

7

Operand

Operator

Operand

Embedded systems and instruction sets

Unit 3 Computer architecture and storage

Opcodes and operands

• When programming a processor a special language

called assembly code is used

• The program is then assembled into a binary form known as

machine code – this is what is run by the processor

• The assembly code (and machine code) make use of

opcodes and operands

• The opcode is the instruction and the operands are the values

that the instruction works on

Instruction:

STO

057

ACC

Opcode

Operand

Operand

Store…
…into memory
address 057…

…the contents

of the accumulator

Multiple Choice

What does an instruction set refer to in the context of a processor?

• A. The speed at which instructions are executed

• B. All the possible instructions that can be executed by a processor

• C. The size of the processor's cache memory

• D. The number of cores in the processor

Multiple Choice

Why won't a program written for an Intel Core i7 work on an ARM processor in a smartphone?

• A. The Intel Core i7 has a faster clock speed

• B. Different types of memory are used in the two processors

• C. The ARM processor has a different instruction set

• D. The Intel Core i7 has more cache memory

Multiple Choice

In ordinary Maths and programming, what does an operator do?

• A. Performs an operation on the operand(s)

• B. Carries out control signals in the CPU

• C. Retrieves data from the cache memory

• D. Transmits data along the address bus

Multiple Choice

What is the purpose of assembly code when programming a processor?

• A. To represent high-level programming languages

• B. To serve as a high-level programming language

• C. To provide a graphical user interface for programming

• D. To represent low-level instructions that the processor can execute

Multiple Choice

What is machine code in the context of programming a processor?

• A. A high-level programming language

• B. A graphical representation of program flow

• C. Binary code that the processor directly executes

• D. A set of assembly instructions

Multiple Choice

What are opcodes and operands in the context of assembly code?

• A. Opcode is the type of processor, and operands are the memory addresses

• B. Opcode is the instruction, and operands are the values the instruction works on

• C. Opcode is the result of an operation, and operands are the input values

• D. Opcode is the program counter, and operands are the data being processed

Multiple Choice

Why won't a program written in assembly code for one type of CPU work on another CPU?

• A. Assembly code is not a programming language

• B. Different CPUs have different clock speeds

• C. Each CPU has its own instruction set

• D. Assembly code is not compiled

Multiple Choice

In programming, what does the term "instruction set" specifically refer to?

• A. The set of instructions for installing a software

• B. The set of instructions executed by the CPU

• C. The set of programming languages available

• D. The set of control signals in a computer system

Multiple Choice

How does assembly code relate to machine code?

• A. Assembly code is a higher-level language than machine code

• B. Assembly code is a graphical representation of machine code

• C. Assembly code is translated into machine code for execution

• D. Assembly code is not used in programming processors

Embedded systems and instruction sets

Unit 3 Computer architecture and storage

Worksheet 5

• Complete Task 1

•Processors are designed to run
and understand a particular set
of 1s and 0s. These are the two
processor instruction sets:

1.

Reduced Instruction
Set(RISC)

2.

Complex Instruction
Set(CISC)

Processor Instruction Set

HIGH LEVEL
LANGUAGE

PRINT (“HELLO”)

ASSEMBLY
LANGUAGE

LDA,MULT,STA

MACHINE CODE

010100101

Processor Level

The processor will need to
understand the 01010010
and this instruction set will
have been embedded in its

design(RISC or CISC)

Compiler
/Interpreter
Converts HLL to
LLL

1.

Complex Instruction
Set(CISC)

•

Used in earlier generations of
computers. Most common in
embedded systems.

•

Designed to complete task with
as few assembly language lines
as possible

•

Processor is capable of
understanding even with a few
instructions because included in
a CISC instruction is a
LOAD/STORE sub instruction
which is executed along with
the calculation.

Processor Instruction Sets

High level

Language
a = a * b

Assembly

Language
for CISC
processor
MULT A,B

2. Reduced Instruction

Set(RISC)

•

More modern processors
where only simple
instructions are used and
executed, each taking one
clock cycle

•

The disadvantage is that the
compiler has to do more
work to translate high level
code into machine code and
more RAM is required to
store the instructions.

•

Its possible to have the
same execution speed as
CISC through pipelining.

Processor Instruction Sets

High level Language

a = a * b

Assembly Language

for RISC
processor

LDA R1, A
LDA R2, B

MULT, R1,R2

STA R1,A

• What is an Instruction Set?
• Describe the difference between RISC and

CISC processors

•

• An assembly language statement

consists of four parts

CMPR1, #10 ‘Compare the value in register

1 with the value 10’

Understanding Assembly Language

CMP – Operation Code
(Opcode)
A Mnemonic that uses 3-
4 characters to explain
the command e.g ADD,
MOV

R1 – Operands
Follows an Opcode and
determines with what the
opcode is to perform. In
this example,
CMP(compare) has to be
followed by two
operands. R1 is a register,
the second operand is the
value denoted by a #10

This is a
Comment

# depicts the
Addressing Mode
Immediate
addressing mode –
the value after the
hash is the actual
data item

• When accessing anything held in memory,

you need to know the address. Data is input
or copied out of memory in two different
ways:

• Direct Addressing – Tells the CPU which

addresscontains the data you want to access
LDA r1,100

• Immediate Addressing – Depicted with a

hash# - The actual data to be operated on
follows the hash eg MOV r1,#10

Addressing Modes

Multiple Choice

In the following assembly code instruction, what does the opcode represent?
ADD R1, R2, R3

• A. The result of the addition operation

• B. The register where the result is stored

• C. The type of operation to be performed (addition)

• D. The memory address of the operand

Multiple Choice

What does the operand #10 represent in this instruction?

SUB R4, R5, #10

• A. A register address

• B. An immediate value

• C. The result of the subtraction

• D. A memory address

Multiple Choice

What is the purpose of the following assembly code instruction?

MOV R6, #255

• A. Move the content of register R6 to register #255

• B. Move the immediate value 255 into register R6

• C. Perform a conditional move operation

• D. Move the content of register #255 to register R6

Multiple Choice

In the instruction JMP Label1, what does the opcode JMP signify?

• A. Jump

• B. Move

• C. Add

• D. Subtract

Multiple Choice

What does the CMP opcode typically indicate?

CMP R7, #0

• A. Compare

• B. Copy

• C. Compute

• D. Complement

CPU architecture

Unit 3 Computer architecture and storage

Microprocessor

• A microprocessor is an integrated circuit that is all

contained on a single chip

• CPUs contain one type of microprocessor, they include

Pentium microprocessors and ARM microprocessors

• Microcontrollers contain not only the

microprocessor, but also RAM and
ROM, or flash memory for volatile and
non-volatile storage – this allows
for an entire computer to
be contained on one chip

CPU architecture

Unit 3 Computer architecture and storage

Embedded systems

• Do these devices have inputs, processes and

outputs?

• Could they be classed as computers?

• Why or why not?

CPU architecture

Unit 3 Computer architecture and storage

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 small computer that forms part of a larger system, device or machine.

Its purpose is to control the device and to allow a user to interact with it.

CPU architecture

Unit 3 Computer architecture and storage

Embedded systems

• Without embedded systems, a digital device

would not be able to perform specific functions

• For example, a dishwasher wouldn’t know when

to heat the water, or a satnav wouldn’t know how
to communicate with a satellite

• What embedded functions do cars use?

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)

CPU architecture

Unit 3 Computer architecture and storage

Other embedded systems

• Embedded systems are also used in:

• Security systems

• Lighting systems

• Vending machines

CPU architecture

Unit 3 Computer architecture and storage

Embedded vs General purpose

• The following table shows how the characteristics of

embedded systems compare to
general purpose machines

Characteristic

Embedded system

General purpose machine

CPU speed

Typically slow

Typically very fast

Software

Has one purpose and
cannot install new software

New software can be
installed

Storage

Programs stored on ROM

Programs stored on
hard drives

Reliability

Typically very reliable – e.g.
a microwave should not
have a bug that changes
defrost to full power

As it runs many software
programs it may be less
reliable and need restarting
the device

CPU architecture

Unit 3 Computer architecture and storage

Worksheet 3

• Complete Task 2 on Worksheet 3

Embedded systems and instruction sets

Unit 3 Computer architecture and storage

Plenary

• Work with a partner to explain

the following terms:

• Embedded system

• Microprocessor

• Instruction set

• Assembly code

• Machine code

• Opcode and operands

Embedded systems and instruction sets

Unit 3 Computer architecture and storage

Plenary

• Embedded system – a single processor that includes, RAM,

ROM and processor as one unit

• Microprocessor – a type of integrated circuit on a single chip

• Instruction set – a list of all the commands that can be

processed by a CPU

• Assembly code – code written in assembly language. The

instructions written are exact 1:1 representations of the
machine code that will be executed on the CPU

• Machine code – The binary representation of the assembly

code program. This will be executed by the CPU

• Opcode and operands – The opcode is the instruction and the

operands are the values that the instruction works on

Objectives

• Understand the meaning of primary storage

including the role of:

• Random Access Memory (RAM)

• Read Only Memory (ROM)

• Describe the difference between RAM and ROM

and why both are needed

• Describe what is meant by virtual memory including:

• How it is created and used

• The reason it is necessary

CPU architecture

Unit 3 Computer architecture and storage

Starter

• What are four types of

memory that are used
in computers systems?

CPU architecture

Unit 3 Computer architecture and storage

Starter

• From previous lessons:

• CPU registers

• Cache

• This lesson:

• RAM

• ROM

• Virtual memory

CPU architecture

Unit 3 Computer architecture and storage

What is Memory

Memory is where binary data (0s and 1s) is
stored.

The term memory is used interchangeably with
storage in the syllabus.

There are several devices in a modern computer
which store data. They store this data in different
ways and for different purposes.

CPU architecture

Unit 3 Computer architecture and storage

Types of primary storage

• There are many types of memory used in

computers

• In the Von Neumann architecture, primary storage

is directly accessed by the CPU

• The two types used as primary storage are:

• RAM (Random Access Memory)

• ROM (Read Only Memory)

RAM

ROM

Memory

Unit 3 Computer architecture and storage

RAM

• RAM stores programs or data that are currently

running or open

• It is directly accessed by the CPU

• When your computer is turned off, data stored in RAM is lost

• RAM is volatile as it loses data if the power is off

• All your programs and data are stored permanently

on your hard drive

• This is known as non-volatile storage as it doesn’t lose the

data if the power is off

CPU architecture

Unit 3 Computer architecture and storage

Worksheet 4

• Complete Task 1 on Worksheet 4

CPU architecture

Unit 3 Computer architecture and storage

RAM

• When the computer is first turned on,

no data is stored in RAM

RAM

Empty

CPU architecture

Unit 3 Computer architecture and storage

Operating system

• The computer first loads the operating

system from your hard drive into RAM

Operating

system

RAM

CPU architecture

Unit 3 Computer architecture and storage

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

Documents

in use

CPU architecture

Unit 3 Computer architecture and storage

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

CPU architecture

Unit 3 Computer architecture and storage

Virtual memory

• Virtual memory is part of the

hard drive used as an
extension to RAM

• A pageof data is a fixed-length

block of virtual memory

• When pages of data are moved

between RAM and hard disk this is
known as swapping or paging

• 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

CPU architecture

Unit 3 Computer architecture and storage

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

CPU architecture

Unit 3 Computer architecture and storage

Whathappens when RAM
completely fills up?

CPU architecture

Unit 3 Computer architecture and storage

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?

CPU architecture

Unit 3 Computer architecture and storage

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

CPU architecture

Unit 3 Computer architecture and storage

RAM vs ROM differences

Characteristic

RAM

ROM

Size

Typically 4 GB – 32 GB

Typically 4 MB – 8 MB

Used to store

Running programs and
operating system

BIOS and bootstrap

Read ability

Yes

Yes

Write ability

Yes

No

Volatile

Yes

No

CPU architecture

Unit 3 Computer architecture and storage

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

CPU architecture

Unit 3 Computer architecture and storage

Worksheet 4

• Complete Task 2 on Worksheet 4

CPU architecture

Unit 3 Computer architecture and storage

Exam Question

1. Abeel had a power cut whilst working on a
spreadsheet document. He said that he lost the entire
document but could still open the spreadsheet
program when the power came back on.

Explain why this was the case for Abeel.

2. An increase in RAM capacity can improve the
performance of your computer.

Explain why an increase in ROM size would not have
the same effect.

CPU architecture

Unit 3 Computer architecture and storage

Exam Question Solution

1. The spreadsheet program was stored on the hard

drive and copied to RAM / main memory while the
program was in use.[1] The document was created
and stored in RAM[1], and disappeared because it
was never saved[1]. If the document had been
saved, it would have been copied to the hard
disk[1].

2. ROM is only required to be as large as the start-up
instructions / BIOS inside it.[1] Any additional space
will make no difference.[1] New files cannot be written
into new space as it is read-only.[1]

CPU architecture

Unit 3 Computer architecture and storage

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?

CPU architecture

Unit 3 Computer architecture and storage

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

Copyright

© 2021 PG Online Limited

The contents of this unit are protected by copyright.

This unit and all the worksheets, PowerPoint presentations, teaching guides and other associated files distributed
with it are supplied to you by PG Online Limited under licence and may be used and copied by you only in
accordance with the terms of the licence. Except as expressly permitted by the licence, no part of the materials
distributed with this unit may be used, reproduced, stored in a retrieval system, or transmitted, in any form or by
any means, electronic or otherwise, without the prior written permission of PG Online Limited.

Licence agreement

This is a legal agreement between you, the end user, and PG Online Limited. This unit and all the worksheets,
PowerPoint presentations, teaching guides and other associated files distributed with it is licensed, not sold, to
you by PG Online Limited for use under the terms of the licence.

The materials distributed with this unit may be freely copied and used by members of a single institution on a
single site only. You are not permitted to share in any way any of the materials or part of the materials with any
third party, including users on another site or individuals who are members of a separate institution. You
acknowledge that the materials must remain with you, the licencing institution, and no part of the materials may
be transferred to another institution. You also agree not to procure, authorise, encourage, facilitate or enable any
third party to reproduce these materials in whole or in part without the prior permission of PG Online Limited.

CPU architecture

Unit 3 Computer architecture and storage

Objectives

• Understand the need for secondary storage

• Describe the operation of the following types of

storage and give examples of each:

• Magnetic storage

• Optical storage

• Solid-state storage

CPU architecture

Unit 3 Computer architecture and storage

Starter

• RAM is a type of primary storage

• It has a fast data rate but is volatile

(the data is lost if there
is no power)

• What storage

devices are
used that are
non-volatile?

CPU architecture

Unit 3 Computer architecture and storage

Secondary storage

• Secondary storage is not directly

accessed by the CPU and is needed
for permanent storage of data

• 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?

CPU architecture

Unit 3 Computer architecture and storage

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

CPU architecture

Unit 3 Computer architecture and storage

Storage types

• Primary storage

• RAM and ROM

• Secondary storage

• Hard Disk Drive (HDD)

• Solid State Drive (SSD)

• Offlinesecondary storage

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

• Flash memory, SD cards

• Removable HDD or SSD

• Magnetic tape

CPU architecture

Unit 3 Computer architecture and storage

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 (NAND technology) without any moving parts

CPU architecture

Unit 3 Computer architecture and storage

Worksheet 9

• Complete Task 1

CPU architecture

Unit 3 Computer architecture and storage

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

CPU architecture

Unit 3 Computer architecture and storage

Hard disks

• Parts of a hard disk

Drive read/write head reads data
on the drive using electromagnets

Magnetic platter
contains data –
Hard disks may
contain more than
one platter

Drive spindle
rotates

Actuator
moves the
read/write arm

CPU architecture

Unit 3 Computer architecture and storage

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 cheaper 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

CPU architecture

Unit 3 Computer architecture and storage

Magnetic storage

• Advantages:

• Cheaper, 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

CPU architecture

Unit 3 Computer architecture and storage

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

CPU architecture

Unit 3 Computer architecture and storage

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)

CPU architecture

Unit 3 Computer architecture and storage

How CDs work

CPU architecture

Unit 3 Computer architecture and storage

CDs, DVDs and BluRay

• Why are the capacities of these discs different given

they are all the same physical size?

• Microscopic view of the surface of a CD ROM

CPU architecture

Unit 3 Computer architecture and storage

• A CD has bigger pits and lands than Blu-ray as red

light has a larger wavelength

• The smaller Blu-ray pits and lands allow it to store more data

Pit size and laser wavelength

CPU architecture

Unit 3 Computer architecture and storage

Worksheet 9

• Complete Task 2 and Task 3

CPU architecture

Unit 3 Computer architecture and storage

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

CPU architecture

Unit 3 Computer architecture and storage

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

CPU architecture

Unit 3 Computer architecture and storage

Flash memory

• Low cost, portable, no moving parts, durable

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

• Cameras

• Mobile phones

• USB memory sticks

CPU architecture

Unit 3 Computer architecture and storage

How flash memory stores data

• A floating gate may store or not store electrons

• If no electrons are present in the floating gate the current will

flow, representing a 1

• If electrons are stored in the floating gate, the current doesn’t

flow, representing a 0

Control Gate

Isolation Layer

Floating Gate

Isolation Layer

SOURCE

DRAIN

Control Gate

Isolation Layer

Isolation Layer

SOURCE

DRAIN

Control Gate

Isolation Layer

Isolation Layer

SOURCE

DRAIN

Electrons

1

0

CPU architecture

Unit 3 Computer architecture and storage

The isolation layer

• The isolation layers are semiconductors known

as transistors

• In order to write to the flash memory cell, the electrons need

to pass through the isolation layer

• The electrons only move through this layer when writing

• Normally, they remain trapped in the floating gate

Control Gate

Isolation Layer

Isolation Layer

SOURCE

DRAIN

Electrons are
trapped

CPU architecture

Unit 3 Computer architecture and storage

How flash memory writes data

• The control gate is used to move electrons into or

out of the floating gate

• A negative voltage forces electrons out of the floating gate

• A positive voltage forces electrons into the floating gate

Control Gate

Isolation Layer

Floating Gate

Isolation Layer

SOURCE

DRAIN

-ve voltage

Isolation Layer

Isolation Layer

SOURCE

DRAIN

+ve voltage

Isolation Layer

Isolation Layer

SOURCE

DRAIN

Electrons

CPU architecture

Unit 3 Computer architecture and storage

Solid-state (flash memory)

• Two types of flash memory are available

• NOR flash memory is used for programs

• Reading from NOR flash is random access like RAM

• It is used to store code such as the BIOS and possibly an

operating system and code is executed directly by the CPU

• NAND memory is used for data storage

• NAND memory works like other secondary storage

• Data is first copied to RAM before it is accessed by the CPU

CPU architecture

Unit 3 Computer architecture and storage

Worksheet 9

• Complete Task 4

CPU architecture

Unit 3 Computer architecture and storage

Plenary

• In pairs, give answers to the following:

• Name 5 components inside a hard disk drive

• Name 4 components on a DVD or inside a DVD drive

• Name 3 technologies that storage

devices use

• Name 2 parts of a

memory cell in
solid state storage

• Name 1 word that

means 1024 Gibibytes

CPU architecture

Unit 3 Computer architecture and storage

Plenary

• Name 5 components inside a hard disk drive

Track, sector, platter, spindle/motor, read/write head, actuator

• Name 4 components on a DVD or inside a DVD drive

Pit, land, laser, light sensor, prism

• Name 3 technologies that storage devices use

Magnetic, optical, solid-state

• Name 2 parts of a

memory cell in solid
state storage
Control gate, floating
gate, isolation layer

• Name 1 word that means

1024 Gibibytes - Mebibyte

Copyright

© 2021 PG Online Limited

The contents of this unit are protected by copyright.

This unit and all the worksheets, PowerPoint presentations, teaching guides and other associated files distributed
with it are supplied to you by PG Online Limited under licence and may be used and copied by you only in
accordance with the terms of the licence. Except as expressly permitted by the licence, no part of the materials
distributed with this unit may be used, reproduced, stored in a retrieval system, or transmitted, in any form or by
any means, electronic or otherwise, without the prior written permission of PG Online Limited.

Licence agreement

This is a legal agreement between you, the end user, and PG Online Limited. This unit and all the worksheets,
PowerPoint presentations, teaching guides and other associated files distributed with it is licensed, not sold, to
you by PG Online Limited for use under the terms of the licence.

The materials distributed with this unit may be freely copied and used by members of a single institution on a
single site only. You are not permitted to share in any way any of the materials or part of the materials with any
third party, including users on another site or individuals who are members of a separate institution. You
acknowledge that the materials must remain with you, the licencing institution, and no part of the materials may
be transferred to another institution. You also agree not to procure, authorise, encourage, facilitate or enable any
third party to reproduce these materials in whole or in part without the prior permission of PG Online Limited.

CPU architecture

Unit 3 Computer architecture and storage

Objectives

• Understand what is meant by cloud storage

• Explain the advantages and disadvantages of storing data on

the cloud in comparison to storing it locally

Cloud storage

Unit 3 Computer architecture and storage

Starter

• Many people and companies

now use the cloud

• What is the cloud?

Cloud storage

Unit 3 Computer architecture and storage

The cloud

• The cloud is another name for services

offered via the Internet

• The name comes from network diagrams

that use a cloud symbol to represent
the Internet

• The cloud can be split into two

major areas:

• Cloud storage

• Cloud computing

• What is cloud storage?

Cloud storage

Unit 3 Computer architecture and storage

Cloud storage

• Cloud storage allows users to

store files and data on
the Internet

• The files are accessed remotely

by users

• Data may be stored in

multiple locations

• A professional company will manage

the data storage

• What are two other cloud storage features?

Cloud storage

Unit 3 Computer architecture and storage

Cloud storage features

• Further features include:

• Synchronisation of devices

with the cloud storage

• 24/7 Availability

• Redundancy

• Multiple file versions

• Only pay for storage used

• Scalability

• What do each of these

features mean?

Cloud storage

Unit 3 Computer architecture and storage

Redundancy

• Storage redundancy is where multiple copies of

files are stored in different locations

• In local storage this is normally carried out by having multiple

copies of files on two different hard drives in one server

• In cloud storage the locations that store redundant files may

be anywhere in the world

Cloud storage

Unit 3 Computer architecture and storage

Scalability

• Scalability is the ability of the storage system or

cloud computing resources to increase in size

• A home PC doesn’t have scalable storage. It may be possible

to have two or three hard disks, but not two or three hundred

• Cloud storage normally charges for the amount of

storage used

• Increasing offline storage usually requires

the purchase of new disks

Cloud storage

Unit 3 Computer architecture and storage

Data centres

• Data centres are buildings that

are dedicated to storing
physical servers

• Each server will contain an array

of hard drives

• Professional engineers will manage

the computers

• The buildings will have temperature

control and air conditioning

• Uptimes for data centres are often

better than 99.99%

Cloud storage

Unit 3 Computer architecture and storage

Worksheet 11

• Complete Task 1 and Task 2

Cloud storage

Unit 3 Computer architecture and storage

Privacy

• If data is stored in the cloud, the

security and privacy of the data
is controlled by an
external company

• Data stored locally is under the

control of a single person or organisation

• Both cloud storage and local storage

may be hacked, however, typically
cloud storage will be more secure

• Companies and organisations will need

to consider the level they trust an
external company to hold their data

Cloud storage

Unit 3 Computer architecture and storage

Data transfer speeds

• When a file is used that is on cloud storage it must

first be downloaded

• With a fast connection and a small office document this may

happen in a few seconds

• However, with files such as those used in video editing it may

take hours to open or save files to cloud storage

• Local storage is very fast to transfer data

• A local SATA solid state drive can read and write data at

around 500 MB per second

• A typical UK internet connection operates at around 70 Mb/s

giving speeds of less than 10 MB per second

Cloud storage

Unit 3 Computer architecture and storage

Worksheet 11

• Complete Task 3

Cloud storage

Unit 3 Computer architecture and storage

Plenary

• Work in a pair to answer the

following questions:

• What is cloud storage?

• How does it differ

from local storage?

• What are two

advantages and
disadvantages of
cloud storage
compared to
local storage?

Cloud storage

Unit 3 Computer architecture and storage

Plenary

• What is cloud storage? Remote storage provided by a

company that is bought as a service

• How does it differ from local storage? Local storage consists

of hard drives that are owned and maintained by the user or
organisation themselves

• What are two advantages and disadvantages of cloud

storage compared to local storage? Some suggestions:

Cloud storage advantages

Cloud storage disadvantages

Redundancy in many remote
locations

Takes longer to download data
in the case of a full restore

Managed by the cloud storage
provider

Not appropriate for large files
where quick access is needed

Copyright

© 2021 PG Online Limited

The contents of this unit are protected by copyright.

This unit and all the worksheets, PowerPoint presentations, teaching guides and other associated files distributed
with it are supplied to you by PG Online Limited under licence and may be used and copied by you only in
accordance with the terms of the licence. Except as expressly permitted by the licence, no part of the materials
distributed with this unit may be used, reproduced, stored in a retrieval system, or transmitted, in any form or by
any means, electronic or otherwise, without the prior written permission of PG Online Limited.

Licence agreement

This is a legal agreement between you, the end user, and PG Online Limited. This unit and all the worksheets,
PowerPoint presentations, teaching guides and other associated files distributed with it is licensed, not sold, to
you by PG Online Limited for use under the terms of the licence.

The materials distributed with this unit may be freely copied and used by members of a single institution on a
single site only. You are not permitted to share in any way any of the materials or part of the materials with any
third party, including users on another site or individuals who are members of a separate institution. You
acknowledge that the materials must remain with you, the licencing institution, and no part of the materials may
be transferred to another institution. You also agree not to procure, authorise, encourage, facilitate or enable any
third party to reproduce these materials in whole or in part without the prior permission of PG Online Limited.

CPU architecture

Unit 3 Computer architecture and storage