Chapter 4 - Processor Fundamentals.pdf

Computer Science
Prepared by: Merbert J. Jeruela, Brainworks-Total International School
Based on 2024-2025 9618 AS/A Level Computer Science Syllabus

Chapter 4: Processor Fundamentals

Something to tickle you ☺
Why did the computer keep its room tidy?
• Because it didn't want to catch a virus!
Why was the computer cold?
• It left its Windows open!

Chapter 4: Processor Fundamentals > What you should already know?

Chapter 4: Processor Fundamentals > What you should already know>Main components of a computer system

Input is the data that is entered into a computer system. This data can be in the
form of text, numbers, images, or audio.
Examples:
•Keyboard: A keyboard is used to enter text and numbers.
•Mouse: A mouse is used to point and click on items on the screen.
•Scanner: A scanner is used to scan images and documents into a computer.
•Microphone: A microphone is used to record audio into a computer.

Processing is the act of converting input data into output data.
The processing unit is responsible for processing data. The processing
unit is also known as the central processing unit (CPU).
The CPU is the "brain" of the computer.
It is responsible for executing instructions and performing calculations.

Storage is the act of saving data for later use. Storage devices are used to store
data.
Examples:
•Hard disk drive (HDD): A hard disk drive is a magnetic storage device that
stores data on platters.
•Solid-state drive (SSD): A solid-state drive is a flash memory storage device
that stores data on memory chips.

Output is the data that is produced by a computer system. Output devices are
used to display output data.
Examples:
•Monitor: A monitor is used to display text and images.
•Printer: A printer is used to print text and images onto paper.
•Speakers: Speakers are used to play audio.

CPU Block Diagram

Chapter 4: Processor Fundamentals > What you should already know>Tablets vs laptop devices in terms of operations
Parameters Explanation

Chapter 4: Processor Fundamentals > What you should already know> tablet vs mobile phones
Explanation
When deciding on which computer, tablet or phone to buy, which are the main factors that determine your
final choice?
Factors

Chapter 4: Processor Fundamentals > What you should already know> tablet vs mobile phones
Factors Explanation
When deciding on which computer, tablet or phone to buy, which are the main factors that determine your
final choice?

Chapter 4: Processor Fundamentals > What you should already know> common physical ports
Look at a number of computers, laptops and phones and list (and name) the types of input and output ports
found on each device.
PC
laptop

Chapter 4: Processor Fundamentals > What you should already know> Microprocessors. Over the years
At the center of all of the above electronic devices is the microprocessor. How has the development of the
microprocessor changed over the last ten years?
Features Explanation
Changes

Chapter 4: Processor Fundamentals
Lesson Proper

Chapter 4: Processor Fundamentals>4.1.1 Von Neumann CPU Model/Architecture> Objectives
By the end of the lesson, you will be able to:
• Define what a CPU architecture is and state its purpose.
• Explain how Von Neumann model influences current CPU
designs/architecture.
• Identify the features of Von Neumann Architecture.
• Draw the basic Von Neumann model of a computer system.

Chapter 4: Processor Fundamentals>4.1.1 Von Neumann Architecture>CPU architecture and its importance
CPU model significantly impacts a computer's processing capabilities, speed, and
overall functionality, making it a pivotal component in the design and performance
of computing systems.

Chapter 4: Processor Fundamentals>4.1.1 Von Neumann Architecture>CPU architecture and its importance
CPU model significantly impacts a computer's processing capabilities, speed, and
overall functionality, making it a pivotal component in the design and performance
of computing systems.
References:
•Hennessy, J. L., & Patterson, D. A. (2011). Computer Architecture: A Quantitative Approach. Morgan Kaufmann.
•Stallings, W. (2016). Computer Organization and Architecture: Designing for Performance. Pearson.

Chapter 4: Processor Fundamentals>4.1.1 Von Neumann Architecture>Von Neumann vs Harvard Model

Chapter 4: Processor Fundamentals>4.1.1 Von Neumann Architecture>Why Von Neumann Architecture?
Prior to Von Neumann Model
So, Von Neumann model solved that problem
• Early computers were fed data while the machines were running.
• It was not possible to store programs or data; that meant they could not
operate without considerable human intervention.
• Jon Von Neumann developed concept of the stored program computer.

Chapter 4: Processor Fundamentals>4.1.1 Von Neumann Architecture>Features of Von Neumann Architecture
• a central processing unit
(CPU or processor)
• a processor able to access
the memory directly
• computer memories that
could store programs as
well as data
• stored programs made up
of instructions that could
be executed in sequential
order.

Chapter 4: Processor Fundamentals>4.1.2 Components of the processor > Objectives
• List the 4 main components of the CPU.
• Explain the functions of each components.

Chapter 4: Processor Fundamentals>4.1.2 Main components of the processor
Arithmetic Logic Unit (ALU)
Control Unit (CU)
System Clock
Immediate Access Store (IAS) - RAM

Chapter 4: Processor Fundamentals>4.1.2 Main Components of the processor> CW1: Functions of the components of the CPU
Access the Google Drive Folder
• Drive Link: https://drive.google.com/drive/folders/16WXPNa4ktxzAM1RR074SfpmFHoNmWjb8?usp=drive_link
• Wait for teacher’s instruction before starting the activity.
• Complete CW1 in 10 minutes

Chapter 4: Processor Fundamentals>4.1.2 Main Components of the processor> 5MPT1: Functions of the components of the CPU
Access the Quiz on Quizzizz
• Quiz Link: Wait for Teacher’s invite.

Chapter 4: Processor Fundamentals>4.1.2 Main Components of the processor> HW1: Functions of the components of the CPU
Get a copy from the teacher
• Return on: November 21, 2023

Chapter 4: Processor Fundamentals>4.1.3 Registers > Objectives
• Define the purpose of registers.
• Distinguish general and special purpose registers.
• List different flags and use them in a given scenario.

Chapter 4: Processor Fundamentals > 4.1.3 Registers > Definition and General Function
Register – A fundamental component of Von Neumann architecture
A small, fast-storage location within CPU to store and quickly
retrieve data.
Can be general or special-purpose.
General purpose - holds data that are frequently used by the CPU.
Example: Accumulator.
Special Purpose - have specific function within CPU and hold the
program state.
Example: holds the current value assigned to a variable
or keep the current count of the loop counter.

Chapter 4: Processor Fundamentals > 4.1.3 Registers > Common Registers
Try this Mnemonic: Cool Islands Make Marvelous Paradise Scenes

Chapter 4: Processor Fundamentals > 4.1.3 Registers > Status Register
• SR is used when instruction requires some form of
arithmetic or logic processing.
Each bit is known as flag.
Common flags:
• Carry flag (C) - is set to 1 if there is a CARRY following
an addition operation.
• Negative flag (N) - is set to 1 if the result of a
calculation yields a NEGATIVE value.
• Overflow flag (O) - is set to 1 if an arithmetic operation
results in an OVERFLOW being produced.
• Zero flag (Z) - is set to 1 if the result of an arithmetic or
logic operation is ZERO.

Chapter 4: Processor Fundamentals > 4.1.3 Registers > Status Register

Chapter 4: Processor Fundamentals > 4.1.3 Registers > Status Register > Discussion
What happens if…
What happens to the status flags when you add two positive numbers that result in a negative
number?
• The overflow flag will be set, indicating that the result of the operation is too large to fit in the
register.
What happens to the status flags when you add two negative numbers that result in a positive
number?
• The carry flag will be set, indicating that the result of the operation generated a carry out.
What happens to the status flags when you divide two numbers that result in a remainder?
• The carry flag will be set, indicating that the result of the operation generated a carry out. The zero
flag will be cleared, indicating that the result of the operation is not zero.

Chapter 4: Processor Fundamentals > 4.1.3 Registers > HW2
Write your answers in your notebook.
• Submit on November 22, 2023.

Chapter 4: Processor Fundamentals > 4.1.4 > System Buses > Objectives
• Explain what are buses in general.
• Distinguish address bus, data bus, and control bus.
• Discuss five factors that affect computer’s performance.

Chapter 4: Processor Fundamentals > 4.1.4 > System Buses
Buses are used in
computers as a parallel
transmission component;
each wire in the bus
transmits one bit of data.
Three common buses used
in the Von Neumann
architecture
• address bus,
• data bus, and
• control bus.

Chapter 4: Processor Fundamentals > 4.1.4 > System Buses > System bus

Chapter 4: Processor Fundamentals > 4.1.4 > System Buses > Types of bus

Chapter 4: Processor Fundamentals > 4.1.4 > System Buses > Why Address Bus is unidirectional?
Why address bus is unidirectional only?
• To avoid a feedback loop. Feedback loop refers to an undesired situation where
addresses generated by the CPU are unintentionally sent back to the CPU through
the address bus.
Analogy: Think of it like sending a letter with an address on it.
• In a feedback loop, the letter could somehow find its way back to the sender, which
is not the intended or efficient way of communication.

Chapter 4: Processor Fundamentals > 4.1.4 > System Buses > Why bus width is important?
In the context of Address Bus:
• The wider the bus, the more memory locations which can be directly addressed at any
given time;
• for example, a bus of width 16 bits can address 216 (65, 536) memory locations,
• whereas a bus width of 32 bits allows 4, 294,967, 296 memory locations to be
simultaneously addressed.

Chapter 4: Processor Fundamentals > 4.1.4 > System Buses > What is a word?
• A word is a group of bits which can be regarded as a single unit, for example, 16-bit, 32-
bit or 64-bit word lengths are the most common).
• Larger word lengths can improve the computer’s overall performance.

Chapter 4: Processor Fundamentals > 4.1.4 > System Buses >More about control bus
• Usually 8-bit size as it only carries control signals.
• System Clock defines clock cycle which synchronizes all computer operations.
• As control bus transmits timing signals, it ensures that everything is fully synchronized.
So,
Increasing
clock speed
Processing
speed of the
CPU is also
increased
While higher clock speeds generally result in increased processing speeds, it's important
to consider a holistic approach to system optimization (Smith, 2021).
current value of clock speed is 3.5GHz
– which means 3.5 billion clock cycles
a second. Meaning, 3.5 billion CPU
operation per second.

Chapter 4: Processor Fundamentals > 4.1.4 > System Buses > 4 other ways to optimize computer system performance
1. Width of the address bus and data bus can affect computer performance.
2. Overclocking: the clock speed can be changed by accessing the basic input/output
system (BIOS) and altering the settings.
However, using a clock speed higher than the computer was designed for can lead to
problems:
• execution of instructions outside design limits, which can lead to seriously
unsynchronized operations (an instruction is unable to complete in time before the next
one is due to be executed)
• the computer would frequently crash and become unstable – serious overheating of the
CPU leading to unreliable performance.

3. The use of cache memory.
• It is similar to RAM in that its contents are lost when the power is turned off.
• Cache uses SRAM whereas most computers use DRAM for main memory.
• Therefore, cache memories will have faster access times, since there is no need to
keep refreshing, which slows down access time.
• Cache memory stores frequently used instructions and data that need to be accessed
faster.
• This improves processor performance.

4. Increasing the number of CPU Cores (one core is made up of an ALU, a CU and the
registers)
• Many computers are dual core or quad core (the CPU is made up of two or four cores).
• This alleviates the need to increase clock speeds.
• However, doubling the number of cores does not necessarily double the computer’s
performance since we have to take into account the need for the CPU to communicate
with each core.

Chapter 4: Processor Fundamentals > 4.1.5 > Computer Ports> Objectives
• Explain the relationship between input/output devices and
the ports.
• Compare and contrast USB, HDMI, and VGA ports.
• Compare and contrast synchronous and asynchronous data
transmission method.

Chapter 4: Processor Fundamentals > 4.1.5 > Computer Ports> Ports and I/O devices
• Input and output devices are connected to a computer system via ports.
• The interaction of the ports with connected input and output is controlled by the control
unit.

Chapter 4: Processor Fundamentals > 4.1.5 > Computer Ports> Types of ports on most modern computers

Chapter 4: Processor Fundamentals > 4.1.5 > Computer Ports> USB Ports
The Universal Serial Bus (USB) is an asynchronous serial data transmission method.
The USB cable consists of a four-wired shielded cable, with two wires for power and the ground, and
two wires used for data transmission.
When a device is plugged into a computer using one of the USB ports:
• The computer automatically detects that a device is present.
• The device is automatically recognized, and the appropriate device driver is loaded up so that
computer and device can communicate effectively
• If driver is not available, the user is prompted to download the appropriate software.

Chapter 4: Processor Fundamentals > 4.1.5 > Computer Ports> USB Ports > Homework 2
1. Compare and contrast synchronous and asynchronous serial
communication.
2. Write your response in your notebook.
Helpful links:
• https://www.electricaltechnology.org/2020/05/difference-between-synchronous-asynchronous-transmission.html
• https://www.geeksforgeeks.org/difference-between-synchronous-and-asynchronous-transmission/

Chapter 4: Processor Fundamentals > 4.1.5 > Computer Ports> USB Ports > Pros and Cons

Chapter 4: Processor Fundamentals > 4.1.5 > Computer Ports> HDMI
High-definition multimedia interface (HDMI) ports allow audio/visual output
from a computer to an HDMI-enabled device.
• support high definition signals.
• replacement of Video Graphics Array (VGA) analogue system.
Modern HD televisions features:
• widescreen format (16:9 aspect ratio).
• screens use a greater number of pixels (typically 1920 × 1080).
• faster refresh rate (such as 120Hz or 120 frames a second).
• range of colors is extremely large (some companies claim up to four
million different color variations)

Chapter 4: Processor Fundamentals > 4.1.5 > Computer Ports> HDMI > Homework 3 > HDCP
1. How does HDMI uses HDCP against piracy?
2. Write your response in your notebook.
Helpful links:
1. https://www.cablematters.com/Blog/HDMI/what-is-hdcp-the-complete-
guide#:~:text=They%20are%20also%20often%20labeled,algorithm%20and%20a%20ha
ndshake%20system.
2. https://www.benq.com/en-ap/knowledge-center/knowledge/what-is-hdcp-and-why-
is-it-important-in-4k.html

Chapter 4: Processor Fundamentals > 4.1.5 > Computer Ports> VGA > A quick look
VGA was introduced at the end of the 1980s.
• VGA supports 640 × 480 pixel resolution on a
television or monitor screen.
• It can also handle a refresh rate of up to 60Hz (60
frames a second) provided there are only 16 different
colors being used.
• If the pixel density is reduced to 200 × 320, then it can
support up to 256 colors.
• The technology is analogue and, as mentioned in the
previous section, is being phased out.

Chapter 4: Processor Fundamentals > 4.1.5 > Computer Ports> HDMI vs VGA > pros and cons

Chapter 4: Processor Fundamentals > 4.1.5 > Computer Ports> 5mpt2
Access the Quiz on Quizzizz

Chapter 4: Processor Fundamentals > 4.1.6 > Fetch-(Decode)-Execute Cycle > Objectives
• Explain the processes involve in fetch-decode-execute cycle.
• Identify the role of registers, buses, ALU and CU in fetch-
decode-execute cycle.

Chapter 4: Processor Fundamentals > 4.1.6 > Fetch-(Decode)-Execute Cycle > Definition
The fetch-execute cycle (instruction cycle)
• a process by which a computer executes instructions, repeatedly.
• One fetch-execute cycle is equivalent to (CPU) one clock cycle.
• i9 intel processors can process an approximate 5.5 billion clock cycle(instructions) in a
second.

Chapter 4: Processor Fundamentals > 4.1.6 > Fetch-(Decode)-Execute Cycle > fetch
Fetch
• The instruction is fetched from the memory
address currently stored in the PC and is then
stored in the CIR.
• The PC is then incremented by 1 so that the next
instruction can be processed.
• This is decoded so that each instruction can be
interpreted in the next part of the cycle.
Register Transfer Notation (RTN)

Chapter 4: Processor Fundamentals > 4.1.6 > Fetch-(Decode)-Execute Cycle > decode
Decode
1. Identifying the Opcode:
Examples:
2. Fetching Operands:
• The actual numbers/data to be added/executed.
• Say, Opcode is 0001 then, operands could be any
2 numbers (in binary form) that needs to be
added. These numbers are currently stored in CIR.

Chapter 4: Processor Fundamentals > 4.1.6 > Fetch-(Decode)-Execute Cycle > execute
Execute
1. The CU passes the decoded instruction as a set of
control signals to the appropriate components. In
this context, it will pass it to the ALU.
2. This allows each instruction to be carried out in its
logical sequence.
3. Result Storage
The result of the operation is stored in the designated
location, which could be a register or memory.
4. Status Update
The processor updates flags or status bits based on
the result, indicating conditions like zero, negative, or
overflow.

Chapter 4: Processor Fundamentals > 4.1.6 > Fetch-(Decode)-Execute Cycle > interrupt process during instruction cycle

Chapter 4: Processor Fundamentals > 4.1.7 : Interrupts > Objectives
• Define what interrupt is.
• Identify reasons that causes an interrupt.

Chapter 4: Processor Fundamentals > 4.1.7 : Interrupts
An interrupt is a signal sent from a device or from software to the processor.
• This will cause the processor to temporarily stop what it is doing and service the
interrupt.
Reasons that causes an interrupt:
• a timing signal (to make sure CPU won’t execute any instruction while interrupt is
being serviced)
• input/output processes (a disk drive is ready to receive more data)
• a hardware fault (paper jam in a printer)
• user interaction (the user pressed a ctrl+alt+del)
• a software error that cannot be ignored (if an .exe file could not be found to initiate
the execution of program).

Chapter 4: Processor Fundamentals > 4.1.7 > Interrupts > 5mpt3
Access the Quiz on Quizizz

Chapter 4 - Processor Fundamentals.pdf

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