1.4 Motherboard and Data Bus

  1.4 Motherboard and Data Bus

 

1.4.1 Explanation of the motherboard's role in connecting components.

 

Motherboard

The motherboard, also called the system board or PCB, is the main circuit board and backbone of the computer that connects and coordinates all components like CPU, RAM, ROM, chips, and ports.

 

Role of Motherboard

The motherboard connects all the main components of a computer—such as the CPU, RAM, storage devices, and input/output ports—through sockets, slots, and buses, allowing them to communicate and work together as a single system.

 

The motherboard serves as a central connector hub in a computer system, facilitating communication and collaboration among components.

 

i. Physical Connections (Plugs & Slots)

• The motherboard has a socket where the CPU (processor) is fixed, and RAM slots (DIMM slots) where the memory modules are installed.

• It has expansion slots (like PCIe slots) for adding extra components such as a graphics card (for gaming and visuals) or a network card (for internet connectivity).

• It also provides various ports for plugging in external devices — such as a monitor, keyboard, mouse, printer, and USB drives.

 

ii. Electrical Connections (Power Supply)

• The PSU (Power Supply Unit) sends electricity to the motherboard.
• The motherboard distributes the right amount of power to each component through circuits and regulators.
• At the same time, it lets electrical signals flow for data transfer.

 

iii. Communication Hub (Data Highways)

• Special chips (Northbridge and Southbridge chipsets) act like traffic police, controlling communication between CPU, RAM, and other devices.
• Internal buses (PCIe, SATA) are like highways that carry data between components.

 

• CPU = City Hall (main controller).
• Northbridge = Highway police for fast lanes (RAM & Graphics).
• Southbridge = Traffic warden for slow lanes (USB, Keyboard, Hard Drive).
• PCIe & SATA = Roads/Highways carrying the vehicles (data).

 

1.4.2 Understanding the data bus and its importance in data transfer.

Buses are connected lines or electronic pathways within a microprocessor chip that link its internal A bus is a set of electronic pathways (like wires) that carry data, addresses, and control signals between the CPU, memory, and input/output devices.

 

Types of buses

1.     Data Bus

2.     Address Bus

3.     Control Bus

Data Bus

The data bus transfers the actual data (0s and 1s) between CPU, memory, and devices. The width of the data bus (8, 16, 32, 64 bits) decides how much data can be transferred at once. It works like a highway for information inside the computer.

 

Importance of Data Bus

The data bus is important because it transfers the actual information being processed, and its width decides the speed and performance of the computer.

 

Address Bus

The address bus carries the address (location) of where data is stored in memory. It is usually one-way, from CPU to memory.

 

Importance of Address Bus

The address bus is important because it tells the computer the exact memory location to fetch or store data. A wider address bus means the computer can use more memory.

 

Control Bus

The control bus carries control signals like read, write, clock, and interrupt to coordinate actions between CPU and other parts.

 

Importance of Control Bus

The control bus is important because it manages the timing and coordination of all operations, ensuring CPU, memory, and devices work together smoothly.

 

1.3 Central Processing Unit (CPU)

  1.3 Central Processing Unit (CPU)

 

·       The CPU (Central Processing Unit) is known as the brain of the computer which receives data from the input unit, processes instructions, and sends results to the output unit.

·       It performs calculations, logical operations, and decision-making tasks essential for running programs and managing system operations.

·       Intel CPUs (e.g., Intel Core i5, i7, i9), AMD CPUs (e.g., Ryzen series, EPYC), Apple CPUs(M1, M2), ARM CPUs ((e.g., Qualcomm Snapdragon, MediaTek)), etc. are popular examples of CPUs.

 

1.3.1 Function of the CPU

 

Fetching - CPU takes (fetches) instructions or data from the main memory (RAM).

Decoding - CPU interprets (decodes) the fetched instructions to understand what action is required.

Executing - CPU carries out the instruction (arithmetic, logic, data movement, or hardware control).

Storing - CPU stores the result in memory or sends it to an output device.

Managing Interrupts - CPU handles signals (interrupts) from hardware or software to ensure smooth and efficient processing.

 

In short with Example (25 + 10):

·        Fetch → Get the problem from memory.

·        Decode → Understand it’s an addition.

·        Execute → Do 25 + 10 = 35.

·        Store → Save result (35) in memory to display.

·        Manage Interrupts → Handle side tasks (e.g., notifications).

 

1.3.2 Components of the CPU: Control Unit, Arithmetic and Logic Unit, and Memory Unit.

 

·       The speed of a computer depends mainly on its microprocessor.

·       The microprocessor has three main parts. Control Unit (CU),  Arithmetic Logic Unit (ALU) and Memory Unit (Registers)

 

Control Unit (CU)

“The Control Unit (CU) directs and coordinates all operations of the computer by controlling the flow of data between the CPU, memory, and input/output devices.”

 

Arithmetic Logic Unit (ALU)

“The Arithmetic Logic Unit (ALU) is the part of the CPU that performs all arithmetic operations (addition, subtraction, multiplication, division) and logical operations (>, <, =, ≠, AND, OR, NOT).”

 

Memory Unit (MU)

The Memory Unit (MU) is the part of the CPU that stores data, instructions, and results temporarily during processing, so they can be quickly accessed by the Control Unit and ALU.

 

Registers

Registers are very small, high-speed storage locations inside the CPU used to hold data, instructions, or results temporarily during processing.”

 

1.2 Input Devices

  1.2 Input Devices

Input devices are hardware components that allow users to enter data and instructions into a computer system, enabling communication between the user and the computer for processing.

Examples of Input Devices:

• Mouse
• Keyboard
• Joystick
• Microphone
• Scanner
• Webcam
• Touchscreen
• Touchpad

 

Mouse

• A mouse is a hand-held pointing input device used to control the movement of the pointer on a computer screen and to give commands through actions like clicking, double-clicking, right-clicking, dragging, and scrolling.
• A standard mouse has three buttons: left button, right button, and scroll wheel.

 

Keyboard

• A keyboard is the most common input device used to enter text, numbers, symbols, and commands into a computer.
• Most common layout = QWERTY (named after first six keys on top row).
• A standard keyboard has 104 keys (more in multimedia keyboards), grouped into alphabet keys, numeric keys, cursor movement keys, function keys, and special purpose keys

 

Joystick

• A joystick is an input device with a stick that can be moved in different directions and is mainly used for controlling movements in video games and simulations.

 

Microphone

• A microphone is an input device that captures sound and converts it into digital signals for communication, recording, and conferencing.
• Common uses: voice chat, video calls, online meetings (Skype, Viber, Zoom, Messenger, etc.).

 

Scanner

• A scanner is an input device that converts physical documents or images into digital format for storage and editing in a computer.
• Example: Scanning printed notes or photos to save in a computer.

 

Webcam

• A webcam is an input device that captures real-time video and audio for online communication, conferencing, and streaming.

 

Touchscreen

• A touchscreen is an input-output device that allows users to interact directly with a computer by touching its display to give commands and view results.
• Examples: Smartphones, Tablets, ATMs, Laptops, POS (billing machines).

 

Touchpad

• A touchpad (trackpad) is a built-in pointing device in laptops that lets users move the cursor and perform clicks by sliding or tapping fingers.

1.1 Introduction to Computer Systems

  1.1  Introduction to Computer Systems

1.1.1 Definition and features of computer system

The word “Computer” comes from the Latin word Computare, which means “to calculate.” In the past, computers were mainly used for calculations, but today they are used everywhere—at home, in schools, offices, hospitals, banks, and many other fields.

A computer is an electronic programmable device that accepts raw data (input) from the user, processes it according to a given set of instructions (software/program), stores data and information for future use, and produces meaningful information (output).

Computers are extremely fast and accurate. They are not only used for solving mathematical problems but also for creating documents, videos, music, presentations, and even games.

Features of a Computer

Computers are powerful and useful in almost every field. Their importance is increasing with time. The main features of computers are:

 1. Automatic

A computer works automatically once instructions are given through software. It can also control other connected devices without human involvement. Example: Printing 1000 pages continuously without monitoring.

 

2. Speed

A computer works with electrical signals (0 and 1 in binary form). These signals travel close to the speed of light, so computers can process millions of instructions in one second. For example, weather forecasting calculations that would take humans hours are done in minutes by a computer. The table below shows the speed of the computer in different units of time.

Unit of Time	Part of second	Power of 10
Millisecond	1/1000	One Thousand (10-3)
Microsecond	1/1000000	One Millionth (10-6)
Nanosecond	1/1000000000	One Billionth (10-9)
Picosecond	1/1000000000000	One Trillionth (10-12)
Femtosecond	1/1000000000000000	One Quadrillionth (10-15)

 3. Accuracy

A computer gives accurate results if correct input and instructions are provided. However:

The incorrect output produced due to incorrect input is referred to as Garbage In Garbage Out (GIGO). Errors due to hardware or software faults are called bugs.

 4. Storage

A computer can store large amounts of data, information, and programs on storage devices (hard disks, CDs, pen drives, etc.). Stored data can be used anytime. 1 Byte = 1 character.

1 Bit = 1 or 0	4 bits = 1 Nibble
8 bits = 1 Byte	1024 bytes = 1 KB
1024 KB = 1 MB	1024 MB = 1 GB
1024 GB = 1 TB	1024 TB = 1 PB
1024 PB = 1 EB	1024 EB = 1 ZB
1024 ZB = 1 YB

KB-Kilobyte, MB-Megabyte, GB-Gigabyte, TB-Terabyte, PB-Petabyte EB-Exabyte, ZB-Zettabyte, YB – Yottabyte

5. Diligence

A computer does not get tired or bored. It can work for long hours with the same speed and accuracy. The capability of a computer to perform a task repeatedly without losing speed and accuracy for a long time is known as diligence.

 6. Versatility

A computer is a versatile (multi-purpose) machine. Versatility refers to the capability of doing various kinds of tasks. It can be used for calculations, preparing documents, designing and research, entertainment (games, music, videos) and communication (emails, messages, file sharing).

 1.1.2 Application Areas of Computer Systems

Computers are very powerful and versatile. They help people work faster, correctly, and more efficiently. With computers, people can prepare documents, spreadsheets, presentations, and graphics. They can also enjoy modern facilities like instant messaging, video chatting, email, online shopping, ticket booking, banking, and getting the latest news. Today, computers are used in almost every field of life. Some important applications are:

 Education

• ·       Computers are widely used in the education sector for both teaching and learning.
• ·       Students can study different subjects through educational websites and online resources.
• ·       Teachers prepare lesson materials, presentations, and multimedia content with the help of computers.
• ·       Schools use computers to maintain student records, prepare bills, and manage exam results efficiently.

 Communication

• ·       Computers play a vital role in sharing information through the Internet.
• ·       They enable services like email, video calls, instant messaging, and social media platforms (e.g., Facebook, Twitter, Instagram) to keep people connected worldwide.

 

Banking

• ·       Computers are used in banks to keep customer records and prepare bank statements.
• ·       People can use online and mobile banking to check balance, transfer money, or pay bills easily.
• ·       Computers also make banking safer and faster by reducing paperwork.

 Medicine

·       Computers are used in hospitals to diagnose diseases with machines like CT scans, ultrasound, and ECG.

·       Hospitals use computers to manage patient records and track medicines.

·       Computers are also used in surgeries and in medical research to discover new treatments.

 Entertainment

• ·       Computers are used for entertainment like playing games, listening to music, watching movies, and browsing the Internet.
• ·       Streaming apps like Netflix and Spotify give access to movies and songs through computers and the Internet.
• ·       Computers let people use social media to talk with others around the world, and they can also be used to make digital drawings and designs.

 Scientific research

• ·       Computers are essential in all forms of scientific study. Scientists use the Internet to get the latest information from around the world.
• ·       Computers are used in weather forecasting, space research, and other complex studies.
• ·       Computers help researchers analyze large amounts of data and run computer experiments (simulations) to understand things better.

 Agriculture

·       Computers make farming more accurate, save time, reduce waste, and increase crop production.

·       Farmers use GPS (Global Positioning System) to find the best areas for planting crops.

·       Drones (small flying machines with cameras) are used to check fields, monitor plant health, and spray fertilizers or pesticides.

·       AI (Artificial Intelligence) helps farmers predict weather, decide when to plant, and how much water or fertilizer to use.

 1.1.3 Functions of a computer system: Input, Process, Output, Storage (IPOS) with Basic Block Diagram.

•  ·       A computer works step by step to change raw data into useful information.
• ·       This process is called the IPOS Cycle: Input → Process → Output → Storage.

 The block diagram of the IPOS cycle of the computer system as:

  

 1. Input

Data is entered into the computer using input devices (keyboard, mouse, scanner, etc.).

 2. Process

The Central Processing Unit (CPU) processes the entered data according to instructions.

 3. Output

The processed information is displayed or given to the user through output devices (monitor, printer, speaker, etc.).

 4. Storage

The data and information can be saved in the computer’s memory (hard disk, pen drive, etc.) for future use.

Learn Class 9 Computer Science - Chapter Computer System.

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- Chapter Computer System

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