Boot the Computer
When a computer is powered on, several key processes occur to ensure the hardware is functioning and the system starts correctly.
🧪 POST (Power-On Self-Test)
- Performed by the BIOS immediately after powering on the system.
- Checks the hardware components to ensure everything is working properly.
- If an error is detected, a beep code or error message is generated.
- Beep codes vary by BIOS and motherboard manufacturer.
- Refer to the motherboard manual for accurate interpretation.
🔧 Tech Tip:
To test POST functionality:
- Remove all RAM and power on the system.
- The system should emit a beep code indicating missing RAM.
- This test is safe and won’t damage the computer.
💾 BIOS (Basic Input/Output System)
- A small program stored on a ROM chip on the motherboard.
- Controls communication between the operating system and hardware.
BIOS Responsibilities:
- Running the POST
- Detecting connected drives and determining bootable devices
- Configuring:
- System memory
- PCIe/PCI expansion slots
- SATA and USB ports
- Power management settings
🧠 CMOS (Complementary Metal Oxide Semiconductor)
- A memory chip that stores BIOS settings (like boot order, time/date, etc.).
- Settings are retained using a small CMOS battery.
⚠️ Warning Sign:
If system time/date resets or is incorrect:
- The CMOS battery may be failing and should be replaced.
🔐 UEFI (Unified Extensible Firmware Interface)
- The modern replacement for legacy BIOS.
- Present in all modern computers.
Key Features:
- Supports 32-bit and 64-bit systems.
- Handles large boot drives (over 2 TB).
- Includes Secure Boot:
- Prevents unauthorized operating systems or malware (e.g., rootkits) from loading at startup.
🛠️ BIOS/UEFI Configuration & Security
🔒 BIOS and UEFI Security
Modern UEFI systems provide more robust security features than legacy BIOS. These features help protect the system and data from unauthorized access or tampering.
Common Security Features:
- Passwords:
- Enable different levels of access (e.g., admin vs user).
- Prevent unauthorized changes to firmware settings.
- Drive Encryption:
- Protects data by encrypting the hard drive.
- Prevents data theft even if the drive is removed.
- LoJack:
- Allows tracking, locking, and wiping a lost or stolen device.
- Often used in laptops and mobile devices.
- Trusted Platform Module (TPM):
- A dedicated chip on the motherboard.
- Stores encryption keys, digital certificates, and passwords securely.
- Used with features like BitLocker in Windows.
- Secure Boot:
- Ensures only trusted, signed operating systems are allowed to load.
- Helps prevent malware such as rootkits from starting during boot.
🔁 Updating the Firmware
BIOS/UEFI firmware updates can improve stability, fix bugs, or add new hardware support.
Evolution of BIOS Updates:
- Legacy BIOS:
- Stored on a ROM chip.
- Updating required physically replacing the chip.
- Modern BIOS/UEFI:
- Stored on EEPROM (Electronically Erasable Programmable Read-Only Memory).
- Can be updated via software — known as “flashing the BIOS”.
⚠️ Update Tips:
- Only download firmware from the official motherboard manufacturer’s website.
- Follow instructions carefully to avoid bricking the system.
- Do not interrupt the power supply during a firmware update.
Advance Computer Concepts
🖥️ Computer Structure
🧠 Central Processing Unit (CPU)
- The CPU is the primary component responsible for fetching, decoding, and executing instructions in a computer.
- It coordinates all activities within the computer system and acts as the “brain” of the system.
Components of the CPU:
- ALU (Arithmetic Logic Unit): Performs mathematical and logical operations.
- Control Unit: Directs the operation of the processor by interpreting instructions.
- Registers: Small, fast storage areas that hold data and instructions temporarily during execution.
- In systems with a single processing unit, this entire structure is referred to simply as the CPU.
⚙️ Core
- A core is an individual processing unit within a processor.
- It can execute instructions independently, making it equivalent to a CPU in single-CPU systems.
Characteristics of Cores:
- A processor can have multiple cores, each capable of processing tasks simultaneously.
- Specialized processing units, such as those found in graphic processing units (GPUs), may also be referred to as cores.
💻 Processor
- A processor is a physical piece of silicon that may contain one or more cores.
- It is the central component responsible for interpreting and executing instructions.
Types of Processors:
- Single-Core Processor: Contains one core, performs tasks sequentially.
- Multicore Processor: Contains multiple cores, allowing parallel processing and more efficient multitasking.
🖥️ CPU Operation
🔄 CPU Speed and Data Processing
- The performance of a CPU is determined by two main factors:
- Speed: Measured in cycles per second (clock speed).
- Megahertz (MHz): Millions of cycles per second.
- Gigahertz (GHz): Billions of cycles per second.
- Data Processing Capacity: The amount of data the CPU can handle at one time, which is influenced by the size of the front-side bus (FSB), also known as the CPU bus or processor data bus.
- Speed: Measured in cycles per second (clock speed).
⚡ Overclocking and CPU Throttling
- Overclocking:
- A technique used to increase the CPU speed beyond its rated specifications.
- While it can lead to faster performance, overclocking can also damage the CPU and may void the warranty.
- Not recommended for general users due to potential heat generation and system instability.
- CPU Throttling:
- The opposite of overclocking, this involves reducing the CPU’s speed to save power or generate less heat.
- Common in mobile devices and laptops to improve battery life and prevent overheating.
🖧 CPU Virtualization
- CPU Virtualization: A hardware feature available on both AMD and Intel processors.
- Enables a single processor to function as if it were multiple independent processors.
- Multiple operating systems can run simultaneously on virtual machines without interfering with each other, as if they were running on separate physical computers.
🧠 Memory
💾 Semiconductor Memory Cells
- Semiconductor memory cells are the fundamental units used in modern memory systems.
Key Characteristics:
- Two States:
- Each memory cell can exist in one of two states, which are used to represent binary 1 and binary 0. These states are the basis for digital data storage.
- Writable:
- The memory cells can be written into (at least once), meaning the state can be set or changed.
- Readable:
- The memory cells can also be read to detect or sense the current state (either 1 or 0).
Addressable Size:
- The smallest unit of data that can be addressed in a memory system is 8 bits, also known as 1 byte.
🧠 RAM (Random Access Memory)
🔄 RAM Overview
- Random Access Memory (RAM) allows both reading and writing data quickly and efficiently.
- It is volatile, meaning that it loses its data when the power is turned off.
⚡ Types of RAM
- DRAM (Dynamic RAM):
- Most common type of RAM used in most computers.
- Cheap to manufacture, consumes less electrical power, and generates less heat.
- Requires frequent refreshing (recharging with power) thousands of times per second to maintain data.
- Volatile: Loses data when power is removed.
2. SRAM (Static RAM):
- Faster than DRAM but also more expensive.
- Volatile: Loses data when power is turned off, just like DRAM.
- Typically used in small amounts for cache memory, offering high-speed data access for the CPU.
📀 Read-Only Memory (ROM)
🔒 ROM Overview
- Non-volatile: ROM retains its data even when the power is turned off.
- Cannot be changed by the user: The data stored in ROM is permanent and typically contains essential software, such as startup instructions or firmware, which is not expected to change throughout the life of the system.
Types of ROM
- PROM (Programmable ROM):
- Non-volatile: Retains data without power.
- One-time programmable: Can be written to only once after the chip is manufactured, typically by a supplier or customer.
- Special programming equipment is required for the writing process, making it a cost-effective way to provide customizable ROM after manufacturing.
2. EPROM (Erasable Programmable ROM):
- Optically erasable: EPROM can be written repeatedly by applying electrical signals, but the data must be erased first before it can be re-written.
- Erased by exposure to UV light: A special UV light is used to erase the data, which is then followed by reprogramming the chip.
3. EEPROM (Electrically Erasable Programmable ROM):
- Electrically erasable: Like EPROM, EEPROM can be written and rewritten, but it does not require erasing the contents first.
- The data can be erased and re-written electrically, making it more convenient for updating data, such as system settings or firmware.
⚡ Flash Memory
📌 Key Features
- Non-volatile: Retains data even when the power is off.
- Inexpensive: Cost-effective compared to other forms of non-volatile memory.
- Secondary storage: Used to store data persistently, like files, apps, and operating systems.
📱 Common Uses
- Portable storage in:
- USB flash drives
- Memory cards (SD cards)
- Solid-state drives (SSDs)
- Embedded in devices like:
- Digital cameras
- Smartphones
- Tablets
- Laptops
⚙️ Technical Characteristics
- Slower rewrite speeds than RAM (but still much faster than traditional hard drives).
- Ideal for flexible start-up instructions and firmware updates.
- Supports multiple write/erase cycles, but performance can degrade over time.
⚡ Cache Memory
🧠 What It Is
- A small, high-speed memory located between the CPU and main RAM.
- Acts as a temporary storage area for data and instructions the CPU is likely to reuse soon.
🚀 Purpose
- Speeds up processing by reducing the time needed to access data from main memory.
- Stores copies of frequently used or recently accessed data from RAM.
📊 Cache Levels
| Level | Location | Speed | Size | Function |
|---|---|---|---|---|
| L1 | Inside CPU core | Fastest | Smallest (~32KB-128KB) | Stores critical data and instructions |
| L2 | Near/inside CPU | Very fast | Larger (~256KB-1MB) | Backup for L1 cache |
| L3 | Shared between cores | Fast | Largest (2MB–30MB+) | Coordinates data across multiple cores |
✅ Benefits
- Reduces latency (time delay) in data access.
- Improves CPU efficiency and overall system performance.
- Especially beneficial in multi-core processors.
💾 Virtual Memory
🧠 What It Is
- A memory management technique that allows the execution of programs larger than the available RAM.
- Uses part of the hard disk or SSD as if it were additional RAM.
🔄 How It Works
- Large programs are divided into parts.
- Only the needed parts are loaded into RAM.
- Unused parts remain on the secondary storage (e.g., hard drive or SSD).
- The system swaps data between RAM and the disk as needed — this process is called paging.
📍 Key Concepts
- Page file / swap file: A reserved space on the disk used for virtual memory.
- Page fault: Occurs when a required part of the program is not in RAM and must be loaded from disk.
✅ Benefits
- Enables multitasking and running large applications.
- Prevents crashes due to lack of physical memory.
⚠️ Drawbacks
- Slower than RAM.
- Excessive use can lead to disk thrashing, which degrades performance.
🔄 RAID Overview
💡 Purpose
RAID is used to:
- Improve performance
- Increase storage capacity
- Provide fault tolerance (data protection in case of drive failure)
🔧 Core Techniques
| Term | Description |
|---|---|
| Striping | Data is split and written across multiple drives. Increases speed, but no redundancy — failure of one drive = total data loss. |
| Mirroring | Data is duplicated onto one or more other drives. Provides redundancy — if one drive fails, data is safe. |
| Parity | Stores checksums that can be used to rebuild lost data. Balances performance and redundancy. |
| Double Parity | Like parity but protects against two simultaneous drive failures. Used in RAID 6. |
📊 Common RAID Levels
| RAID Level | Description | Key Features |
|---|---|---|
| RAID 0 | Striping only | Fast, no fault tolerance |
| RAID 1 | Mirroring | Redundancy, lower capacity |
| RAID 5 | Striping + Parity | Speed + fault tolerance (1 disk) |
| RAID 6 | Striping + Double Parity | Can survive 2 drive failures |
| RAID 10 (1+0) | Striping across mirrored sets | High performance + redundancy |
⚠️ Note
- RAID is not a backup: It improves availability but should still be complemented with external backups.
- Hardware RAID is managed by a RAID controller; Software RAID uses the operating system.
Legacy Ports
Serial
- Used for connecting various peripherals such as printers, scanners,
modems, and console connections to network devices.
Parallel
- Used for connecting to various peripheral devices, commonly printers.
Game
- Used for connecting a joystick input
PS/2
- Used for connecting a keyboard and mouse. Purple for keyboard and
green for the mouse.
Audio Ports
- Analog ports were used for connecting stereo system, microphone and
speakers/headphones.
Video and Graphic Ports
VGA
- An analog port and commonly the oldest graphics port still used on some
PCs.
DVI
- Provides support for transmitting uncompressed digital video.
- Includes DVI-A (analog), DVI-D (digital), and DVI-I (integrated).
HDMI
- Carries the same video information as DVI but is also capable of
providing digital audio and control signals.
Display port
- Designed to replace both DVI and VGA for computer monitors while
including high bandwidth video and audio signals.
USB Cables and Connectors
Over the years, USB has evolved with various standards. (USB 1.0,
USB 2.0, USB 3.0, and USB 3.2)
USB Types-A
- The typical rectangular connector found on almost all desktop and laptop
computers, TVs, game consoles, and media players.
Mini-USB
- A rectangular connector with a small indention on each side that is being
replaced with the micro-USB connector.
Micro-USB
- A common connector on smartphones, tablets and other devices.
- This connector has two corners pushed in at an angle
USB Type-B
- This connector has a square shape with beveled exterior corners and an
extra notch at the top. - Used to connect printers or external hard drives.
USB Type-C
- This connector is rectangular with four rounded corners and is the newest
USB interface. - Used as a multipurpose cable to attach different kinds of peripheral devices
to a PC.
Lightning
- This connector is a small proprietary 8-pin connector used by Apple mobile
devices such as iPhones, iPads, and iPods for both power and data.
SATA Cables and Connectors
SATA Cable
- One end plugs into a SATA port on a motherboard and the other end into
the back of an internal storage device. - The SATA data cable does not provide power, so a SATA power cable is
needed in addition to power the internal storage device. - SATA data and power cables are keyed so they can only be installed in
one way.
eSATA Cable
- This cable is used to connect external SATA drives and is a keyed
connector.
eSATA Adapter
- An expansion card is commonly used to provide eSATA ports
Twisted Pair Cables and Connectors
- Twisted pair cable is used in wired Ethernet networks and older telephone networks (often termed as Ethernet Cable)
Twisted Pairs
- Unshielded Twisted Pair (UTP) cabling is the most common form of
twisted pair cabling and uses color-coded insulated copper wires. - Shielded Twisted Pair (STP) also uses color-coded insulated copper
wires but includes foil or braiding as well.
RJ-45
- Each end of a UTP cable must be terminated with an RJ-45 connector
so it can be plugged into an Ethernet port.
RJ-11
- Older telephone networks used a four-wire UTP cable terminated with
an RJ-11 connector.
Coax Cables and Connectors
Coax Cable Construction
- Coaxial cable has an inner center conductor surrounded by insulating
material. - The insulating material is surrounded by a foil shield which is used as an
outer conductor and also shields against electromagnetic interference (EMI).
RG-6
- A heavy gauge cable with insulation and shielding for high-bandwidth, high-
frequency applications (Internet, Cable TV, and Satellite TV)
RG-59
- A thinner cable similar to RG-6, used for low bandwidth and lower frequency
applications (analog video and CCTV)
BNC
- An older connector, used with digital or analog audio or video.
SCSI and IDE Cables and Connectors
Small Computer Systems Interface (SCSI) is a standard for connecting peripheral and storage devices in a daisy-chained format.
External SCSI Cable
- Used for connecting older external SCSI devices (scanners and printers).
Internal SCSI Cable
- Common SCSI connector for internal hard drives with 50 pins arranged in
two rows and attached to a ribbon cable.
IDE Cable
- Visually similar to the internal SCSI cable, but commonly with three 40-pin
connectors. - One connector connects to the IDE port on the motherboard and two for
attaching IDE drives.
🖥️ Monitor Characteristics
| Term | Description |
|---|---|
| Screen Size | Measured diagonally in inches (corner to corner) |
| Resolution | Total number of pixels displayed (e.g., 1920×1080 = 1080p) |
| Monitor Resolution | Determines how much info fits on the screen |
| Native Resolution | Optimal display resolution for that specific monitor |
| Native Mode | When the display output matches the native resolution |
| Connectivity | Types of video input ports (e.g., VGA, DVI, HDMI, DisplayPort) |
🔍 Monitor Terms
| Term | Meaning |
|---|---|
| Pixel | Smallest display unit (red, green, blue dots) |
| Dot Pitch | Distance between adjacent pixels (smaller = sharper) |
| Brightness | Measured in cd/m² (candela per square meter) |
| Contrast Ratio | Range between darkest black and brightest white |
| Aspect Ratio | Ratio of width to height (e.g., 16:9) |
| Refresh Rate | How often the screen updates per second (Hz) |
| Response Time | Time for a pixel to change (lower = better for motion) |
| FPS (Frames Per Second) | Number of frames generated per second by the GPU |
| Interlaced | Displays odd and even lines in two passes |
| Non-Interlaced | Displays lines in one top-to-bottom pass |
🖼️ Display Standards
| Standard | Resolution | Also Known As |
|---|---|---|
| CGA | 320 × 200 | – |
| VGA | 640 × 480 | – |
| SVGA | 800 × 600 | – |
| HD | 1280 × 720 | 720p |
| FHD | 1920 × 1080 | 1080p |
| QHD | 2560 × 1440 | 1440p |
| UHD | 3840 × 2160 | 4K |
🖥️ Using Multiple Monitors
Configure display settings in the operating system (e.g., Extend/Duplicate mode).
Benefits: Larger desktop area, multitasking, extended display, or mirrored content.
Requirements:
Ensure hardware and GPU support multiple monitors.
Use proper video cables (e.g., HDMI, DisplayPort).
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