Computer Hardware and Basic Networking Concepts.

COMPUTER HARDWARE AND BASIC                      NETWORKING CONCEPTS

Introduction: Computer hardware is the physical parts or components of a computer, such as the monitor, mouse, keyboard, computer data storage, hard disk drive (HDD), graphic cards, sound cards, memory, motherboard, and so on, all of which are physical objects that are tangible.

 Computer hardware: (usually simply called hardware when a computing context is concerned) is the collection of physical elements that constitutes a computer system. Computer hardware is the physical parts or components of a computer, such as the monitor, mouse, keyboard, computer data storage, hard disk drive (HDD), graphic cards, sound cards, memory, motherboard, and so on, all of which are physical objects that are tangible. In contrast, software is instructions that can be stored and run by hardware. Software is any set of machine-readable instructions that directs a computer’s processor to perform specific operations. A combination of hardware and software forms a usable computing system. 

Von Neumann architecture: 

Von Neumann architecture

The template for all modern computers is the Von Neumann architecture, detailed in a 1945 paper by Hungarian mathematician John von Neumann. This describes a design architecture for an electronic digital computer with subdivisions of a processing unit consisting of an arithmetic logic unit and processor registers, a control unit containing an instruction register and program counter, a memory to store both data and instructions, external mass storage, and input and output mechanisms.^[3] The meaning of the term has evolved to mean a stored-program computer in which an instruction fetch and a data operation cannot occur at the same time because they share a common bus. This is referred to as the Von Neumann bottleneck and often limits the performance of the system.

Different systems:

There are a number of different types of computer system in use today.

Personal computer:

Hardware of a modern personal computer: 1. Monitor 2. Motherboard 3.CPU 4. RAM 5. Expansion cards6. Power supply 7. Optical disc drive8. Hard disk drive9. Keyboard 10. Mouse.

The personal computer, also known as the PC, is one of the most common types of computer due to its versatility and relatively low price. Laptops are generally very similar, although may use lower-power or reduced size components.

Power supply:

A power supply unit (PSU) converts alternating current (AC) electric power to low-voltage DC power for the internal components of the computer. Laptops are capable of running from a built-in battery, normally for a period of hours.

Case:

The computer case is a plastic or metal enclosure that houses most of the components. Those found on desktop computers are usually small enough to fit under a desk, however in recent years more compact designs have become more common place, such as the all-in-one style designs from Apple, namely the iMac. Though a case can basically be big or small, what matters more is which form factor of motherboard it’s designed for. Laptops are computers that usually come in a clamshell form factor, again however in more recent years deviations from this form factor have started to emerge such as laptops that have a detachable screen that become tablet computers in their own right.

Mainboard/Motherboard:

The motherboard is the main component of a computer. It is a large rectangular board with integrated circuitry that connects the other parts of the computer including the CPU, the RAM, the disk drives (CD, DVD, hard disk, or any others) as well as any peripherals connected via the ports or the expansion slots.

Components directly attached to or part of the motherboard include:

·         The CPU (Central Processing Unit) performs most of the calculations which enable a computer to function, and is sometimes referred to as the “brain” of the computer. It is usually cooled by a heat sink and fan. Most newer CPUs include an on-die Graphics Processing Unit (GPU).

·         The Chipset, which includes the north bridge, mediates communication between the CPU and the other components of the system, including main memory.

·         The Random-Access Memory (RAM) stores the code and data that are being actively accessed by the CPU.

·         The Read-Only Memory (ROM) stores the BIOS that runs when the computer is powered on or otherwise begins execution, a process known as Bootstrapping, or “booting” or “booting up”. The BIOS (Basic Input Output System) includes boot firmware and power management firmware. Newer motherboards use Unified Extensible Firmware Interface (UEFI) instead of BIOS.

·         Buses connect the CPU to various internal components and to expand cards for graphics and sound.

·         The CMOS battery is also attached to the motherboard. This battery is the same as a watch battery or a battery for a remote to a car’s central locking system. Most batteries are CR2032, which powers the memory for date and time in the BIOS chip.

 

Expansion cards:

An expansion card in computing is a printed circuit board that can be inserted into an expansion slot of a computer motherboard or backplane to add functionality to a computer system via the expansion bus. Expansions cards can be used to obtain or expand on features not offered by the motherboard.

 

Storage devices:

Computer data storage, often called storage or memory, refers to computer components and recording media that retain digital data. Data storage is a core function and fundamental component of computers. The price of solid-state drives (SSD), which store data on flash memory, has dropped a lot in recent years, making them a better choice than ever to add to a computer to make booting up and accessing files faster.

·         Fixed media

o    Data is stored by a computer using a variety of media. Hard disk drives are found in virtually all older computers, due to their high capacity and low cost, but solid-state drives are faster and more power efficient, although currently more expensive than hard drives, so are often found in more expensive computers. Some systems may use a disk array controller for greater performance or reliability.

·         Removable media

o    To transfer data between computers, a USB flash drive or Optical disc may be used. Their usefulness depends on being readable by other systems; the majority of machines have an optical disk drive, and virtually all have a USB port.

 

Input and output peripherals:

Input and output devices are typically housed externally to the main computer chassis. The following are either standard or very common to many computer systems.

·         Input

o    Input devices allow the user to enter information into the system, or control its operation. Most personal computers have a mouse and keyboard, but laptop systems typically use a touchpad instead of a mouse. Other input devices include webcams, microphones, joysticks, and image scanners.

·         Output device

o    Output devices display information in a human readable form. Such devices could include printers, speakers, monitors or a Braille embosser.

Mainframe computer:

An IBM System z9 mainframe.

 

A mainframe computer is a much larger computer that typically fills a room and may cost many hundreds or thousands of times as much as a personal computer. They are designed to perform large numbers of calculations for governments and large enterprises.

 

 

Hardware upgrade

When using computer hardware, an upgrade means adding new hardware to a computer that improves its performance, adds capacity or new features. For example, a user could perform a hardware upgrade to replace the hard drive with an SSD to get a boost in performance or increase the number of files that may be stored. Also, the user could increase the RAM so the computer may run more smoothly. The user could add a USB 3.0 expansion card in order to fully use USB 3.0 devices. Performing such hardware upgrades may be necessary for older computers to meet a programs’ system requirements.

Motherboard:

Motherboard for an Acer desktop personal computer, showing the typical components and interfaces that are found on a motherboard. This model was made by Foxconn in 2007, and follows the ATX layout (known as the “form factor”) usually employed for desktop computers. It is designed to work with AMD’s Athlon 64 processor

 

 

A motherboard (sometimes alternatively known as the mainboard, system board, planar board or logic board, or colloquially, a mob) is the main printed circuit board (PCB) found in computers and other expandable systems. It holds and allows communication between many of the crucial electronic components of a system, such as the central processing unit (CPU) and memory, and provides connectors for other peripherals. Unlike a backplane, a motherboard contains significant sub-systems such as the processor and other components.

 

Motherboard specifically refers to a PCB with expansion capability and as the name suggests, this board is often referred to as the “mother” of all components attached to it, which often include sound cards, video cards, network cards, hard drives, or other forms of persistent storage; TV tuner cards, cards providing extra USB or FireWire slots and a variety of other custom components (the term mainboard is applied to devices with a single board and no additional expansions or capability, such as controlling boards in televisions, washing machines and other embedded systems).

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Intel D945GCPE A micro ATX Motherboard LGA775 for Intel Pentium 4, D, XE, Dual-Core, Core 2

Design:

 

The Octet Jaguar V motherboard from 1993. This board has few onboard peripherals, as evidenced by the 6 slots provided for ISA cards and the lack of other built-in external interface connectors

The motherboard of a Samsung Galaxy SII; almost all functions of the device are integrated into a very small board

A motherboard provides the electrical connections by which the other components of the system communicate. Unlike a backplane, it also contains the central processing unit and hosts other subsystems and devices.

A typical desktop computer has its microprocessor, main memory, and other essential components connected to the motherboard. Other components such as external storage, controllers for video display and sound, and peripheral devices may be attached to the motherboard as plug-in cards or via cables, in modern computers it is increasingly common to integrate some of these peripherals into the motherboard itself.

An important component of a motherboard is the microprocessor’s supporting chipset, which provides the supporting interfaces between the CPU and the various buses and external components. This chipset determines, to an extent, the features and capabilities of the motherboard.

Modern motherboards include:

·         Sockets (or slots) in which one or more microprocessors may be installed. In the case of CPUs in ball grid array packages, such as the VIA C3, the CPU is directly soldered to the motherboard.

·         Slots into which the system’s main memory is to be installed (typically in the form of DIMM modules containing DRAM chips)

·         A chipset which forms an interface between the CPU’s front-side bus, main memory, and peripheral buses

·         Non-volatile memory chips (usually Flash ROM in modern motherboards) containing the system’s firmware or BIOS

·         A clock generator which produces the system clock signal to synchronize the various components

·         Slots for expansion cards (the interface to the system via the buses supported by the chipset)

·         Power connectors, which receive electrical power from the computer power supply and distribute it to the CPU, chipset, main memory, and expansion cards. As of 2007, some graphics cards (e.g. GeForce 8 and Radeon R600) require more power than the motherboard can provide, and thus dedicated connectors have been introduced to attach them directly to the power supply.

·         Connectors for hard drives, typically SATA only. Disk drives also connect to the power supply.

Additionally, nearly all motherboards include logic and connectors to support commonly used input devices, such as PS/2 connectors for a mouse and keyboard. Early personal computers such as the Apple II or IBM PC included only this minimal peripheral support on the motherboard. Occasionally video interface hardware was also integrated into the motherboard; for example, on the Apple II and rarely on IBM-compatible computers such as the IBM PC Jr. Additional peripherals such as disk controllers and serial ports were provided as expansion cards.

Given the high thermal design power of high-speed computer CPUs and components, modern motherboards nearly always include heat sinks and mounting points for fans to dissipate excess heat.

Form factor:

Motherboards are produced in a variety of sizes and shapes called computer form factor, some of which are specific to individual computer manufacturers. However, the motherboards used in IBM-compatible systems are designed to fit various case sizes. As of 2007, most desktop computer motherboards use the ATX standard form factor — even those found in Macintosh and Sun computers, which have not been built from commodity components. A case’s motherboard and PSU form factor must all match, though some smaller form factor motherboards of the same family will fit larger cases. For example, an ATX case will usually accommodate a micro ATX motherboard.

Laptop computers generally use highly integrated, miniaturized and customized motherboards. This is one of the reasons that laptop computers are difficult to upgrade and expensive to repair. Often the failure of one laptop component requires the replacement of the entire motherboard, which is usually more expensive than a desktop motherboard due to the large number of integrated components.

CPU sockets

A CPU socket (central processing unit) or slot is an electrical component that attaches to a Printed Circuit Board (PCB) and is designed to house a CPU (also called a microprocessor). It is a special type of integrated circuit socket designed for very high pin counts. A CPU socket provides many functions, including a physical structure to support the CPU, support for a heat sink, facilitating replacement (as well as reducing cost), and most importantly, forming an electrical interface both with the CPU and the PCB. CPU sockets on the motherboard can most often be found in most desktop and server computers (laptops typically use surface mount CPUs), particularly those based on the Intel x86 architecture. A CPU socket type and motherboard chipset must support the CPU series and speed.

Computer Ports:

Computer ports are a staple part of a motherboard and expansion cards. Just like everything else computer related, ports have evolved in type and performance.

They are simply physical connection points for peripheral/external devices. Follow the wire from your keyboard and see where it plugs into.

In this section we look at the main types of ports and clarify what they are and their uses.

Female PS/2 ports are used to connect older keyboards and mice to computers. In the early days these ports were not color coordinated, or even labelled, to differentiate between which is which. I recall fondly the trial and error of trying to guess the right port for each.

Color co-ordination of each port made things easier. The male connectors on each device were also colored purple and green. The only thing left for you to do was to orientate the pins right so it plugged in OK.

In the IT industry these ports are known as 6-pin mini DIN plugs. For my fellow nerds, DIN stands for Deutsche Institute fuser Norm burg (a German standardization group), and was developed by IBM. They are also known as IEEE 1284-compliant Centronics ports.

The big disadvantage of these ports is if you encountered a keyboard or mouse failure, or if either were accidentally unplugged, you had to switch off your computer, plug back in, then switch back on. Very frustrating, and the trigger of many support calls!

Universal Serial Bus, or USB, is the most commonly used female connector today. Modern computers provide a minimum of 2 USB ports, some have up to 6 at both the front and back of the desktop chassis.

Developed in the mid-1990s, this port is now the default for most directly connected peripheral devices. In theory, they can cope with up to 127 daisy-chained devices. No wonder they were touted as the ultimate replacement of all other port types.

The big advantage of these 4-pin ports is one of the pins runs a 5-volt power supply from the PSU. This means you can charge devices such as mobile phones via your USB port.

Another big advantage is they are plug and play. Accidentally unplug your mouse. No problem. Simply plug back in and carry on working.

Always make sure you safely remove USB connected devices from your machine. Removing the cable or device without doing so can potentially corrupt your data (if it is an external HDD or USB pen for example)

The Registered Jack 45 (RJ45) LAN port, or Ethernet port, is for connecting Cat.5 or Cat.6 Ethernet cables. Everyday users don't usually need to bother with this port, as modern devices are now wireless.

However, in business these ports are still widely used for connecting PC's to the corporate data network. They are also used for a plethora of other type of connectivity, including Wireless Access Points, CCTV Cameras and proximity card readers to name but a few.

The Parallel port and Games port are also legacy. The 25-pin DB parallel port was used for connecting up printers. All are USB these days. Communication (COM) ports are also legacy. They were used for connecting modems, although some older medical equipment still uses these ports.

Audio cards or integrated audio ports normally include a Line In for connecting legacy tape recorders or microphones (Inputs) and a Line-Out for connecting speakers or headphones (Outputs).

Sometimes multiple Input and Output ports are available. Older cards have a games port. Take a look at the sound card definition article for more details. 

To finish off this section, the image below shows the different type of display ports found on computers and graphics cards up to the present day.

All are used to display content on your monitor. There is less need for Video Graphics Array (VGA) as modern LED Monitors are High Definition Multimedia Interface (HDMI) compliant.

From a technician and a home users’ point of view, the cabling that comes with HMDI and more recently, Display Port enabled Light-Emitting Diode (LED) monitors, is much easier to handle and control - thinner, lighter and more flexible than the old Cathode Ray Tube (CRT) type VGA connected monitors.

 

There are lots of other ports that have appeared on the back of computers, and other peripherals such as printers. Secure Digital (SD) cards, FireWire Ports and of course the kettle socket on the PSU all spring to mind.

Next, we take a look at the types of peripheral devices that are associated with modern computers.

Integrated peripherals:

Block diagram of a modern motherboard, which supports many on-board peripheral functions as well as several expansion slots

 

With the steadily declining costs and size of integrated circuits, it is now possible to include support for many peripherals on the motherboard. By combining many functions on one PCB, the physical size and total cost of the system may be reduced; highly integrated motherboards are thus especially popular in small form factor and budget computers.

·         Disk controllers for a floppy disk drive, up to 2 PATA drives, and up to 6 SATA drives (including RAID 0/1 support)

·         integrated graphics controller supporting 2D and 3D graphics, with VGA and TV output

·         integrated sound card supporting 8-channel (7.1) audio and S/PDIF output

·         Fast Ethernet network controller for 10/100 Mbit networking

·         USB 2.0 controller supporting up to 12 USB ports

·         IrDA controller for infrared data communication (e.g. with an IrDA-enabled cellular phone or printer)

·         Temperature, voltage, and fan-speed sensors that allow software to monitor the health of computer components.

Peripheral card slots:

 

A typical motherboard will have a different number of connections depending on its standard and form factor.

A standard, modern ATX motherboard will typically have two or three PCI-Express 16x connection for a graphics card, one or two legacy PCI slots for various expansion cards, and one or two PCI-E 1x (which has superseded PCI). A standard EATX motherboard will have two to four PCI-E 16x connection for graphics cards, and a varying number of PCI and PCI-E 1x slots. It can sometimes also have a PCI-E 4x slot (will vary between brands and models).

Some motherboards have two or more PCI-E 16x slots, to allow more than 2 monitors without special hardware, or use a special graphics technology called SLI (for Nvidia) and Crossfire (for AMD). These allow 2 to 4 graphics cards to be linked together, to allow better performance in intensive graphical computing tasks, such as gaming, video editing, etc.

Temperature and reliability:

A motherboard of a vaio E series laptop

 

 Motherboards are generally air cooled with heat sinks often mounted on larger chips, such as the Northbridge, in modern motherboards. Insufficient or improper cooling can cause damage to the internal components of the computer, or cause it to crash. Passive cooling, or a single fan mounted on the power supply, was sufficient for many desktop computer CPU’s until the late 1990s; since then, most have required CPU fans mounted on their heat sinks, due to rising clock speeds and power consumption. Most motherboards have connectors for additional case fans and integrated temperature sensors to detect motherboard and CPU temperatures and controllable fan connectors which the BIOS or operating system can use to regulate fan speed. Alternatively, computers can use a water-cooling system instead of many fans.

Some small form factor computers and home theater PCs designed for quiet and energy-efficient operation boast fan-less designs. This typically requires the use of a low-power CPU, as well as careful layout of the motherboard and other components to allow for heat sink placement.

Motherboards use electrolytic capacitors to filter the DC power distributed around the board. These capacitors age at a temperature-dependent rate, as their water-based electrolytes slowly evaporate. This can lead to loss of capacitance and subsequent motherboard malfunctions due to voltage instabilities. While most capacitors are rated for 2000 hours of operation at 105 °C (221 °F), their expected design life roughly doubles for every 10 °C (50 °F) below this. At 45 °C (113 °F) a lifetime of 15 years can be expected. This appears reasonable for a computer motherboard. However, many manufacturers deliver substandard capacitors, which significantly reduce life expectancy. Inadequate case cooling and elevated temperatures easily exacerbate this problem. It is possible, but time-consuming, to find and replace failed capacitors on personal computer motherboards.

Air pollution and reliability:

High rates of motherboard failures in China and India appear to be due to “sulfurous air pollution produced by coal that’s burned to generate electricity. Air pollution corrodes the circuitry, according to Intel researchers.

Bootstrapping using the Basic input output system:

Motherboards contain some non-volatile memory to initialize the system and load some startup software, usually an operating system, from some external peripheral device. Microcomputers such as the Apple II and IBM PC used ROM chips mounted in sockets on the motherboard. At power-up, the central processor would load its program counter with the address of the boot ROM and start executing instructions from the ROM. These instructions initialized and tested the system hardware, displayed system information on the screen, performed RAM checks, and then loaded an initial program from an external or peripheral device. If none was available, then the computer would perform tasks from other memory stores or display an error message, depending on the model and design of the computer and the ROM version. For example, both the Apple II and the original IBM PC had Microsoft Cassette BASIC in ROM and would start that if no program could be loaded from disk.

Most modern motherboard designs use a BIOS, stored in an EEPROM chip soldered to or socketed on the motherboard, to booting an operating system. Non-operating system boot programs are still supported on modern IBM PC-descended machines, but nowadays it is assumed that the boot program will be a complex operating system such as MS Windows NT or Linux. When power is first supplied to the motherboard, the BIOS firmware tests and configures memory, circuitry, and peripherals. This Power-On Self-Test (POST) may include testing some of the following things:

·         Video adapter

·         Cards inserted into slots, such as conventional PCI

·         Floppy drive

·         Temperatures, voltages, and fan speeds for hardware monitoring

·         CMOS used to store BIOS setup configuration

·         Keyboard and Mouse

·         Network controller

·         Optical drives: CD-ROM or DVD-ROM

·         SCSI hard drive

·         IDE, EIDE, or SATA Hard disk

·         Security devices, such as a fingerprint reader or the state of a latching switch to detect intrusion

·         USB devices, such as a memory storage device

On recent motherboards, the BIOS may also patch the central processor microcode if the BIOS detects that the installed CPU is one for which errata have been published.

A central processing unit (CPU): is the electronic circuitry within a computer that carries out the instructions of a computer program by performing the basic arithmetic, logical, control and input/output (I/O) operations specified by the instructions. The term has been used in the computer industry at least since the early 1960s. Traditionally, the term “CPU” refers to a processor, more specifically to its processing unit and control unit (CU), distinguishing these core elements of a computer from external components such as main memory and I/O circuitry.

The form, design and implementation of CPUs have changed over the course of their history, but their fundamental operation remains almost unchanged. Principal components of a CPU include the arithmetic logic unit (ALU) that performs arithmetic and logic operations, processor registers that supply operands to the ALU and store the results of ALU operations, and a control unit that fetches instructions from memory and “executes” them by directing the coordinated operations of the ALU, registers and other components.

Most modern CPUs are microprocessors, meaning they are contained on a single integrated circuit (IC) chip. An IC that contains a CPU may also contain memory, peripheral interfaces, and other components of a computer; such integrated devices are variously called microcontrollers or systems on a chip (SoC). Some computers employ a multi-core processor, which is a single chip containing two or more CPUs called “cores”; in that context, single chips are sometimes referred to as “sockets”. Array processors or vector processors have multiple processors that operate in parallel, with no unit considered central.

 Structure and implementation:

Block diagram of a basic uniprocessor-CPU computer. Black lines indicate data flow, whereas red lines indicate control flow; arrows indicate flow directions.

Hardwired into a CPU’s circuitry is a set of basic operations it can perform, called an instruction set. Such operations may involve, for example, adding or subtracting two numbers, comparing two numbers, or jumping to a different part of a program. Each basic operation is represented by a particular combination of bits, known as the machine language opcode; while executing instructions in a machine language program, the CPU decides which operation to perform by “decoding” the opcode. A complete machine language instruction consists of an opcode and, in many cases, additional bits that specify arguments for the operation (for example, the numbers to be summed in the case of an addition operation). Going up the complexity scale, a machine language program is a collection of machine language instructions that the CPU executes.

The actual mathematical operation for each instruction is performed by a combinational logic circuit within the CPU’s processor known as the arithmetic logic unit or ALU. In general, a CPU executes an instruction by fetching it from memory, using its ALU to perform an operation, and then storing the result to memory. Beside the instructions for integer mathematics and logic operations, various other machine instructions exist, such as those for loading data from memory and storing it back, branching operations, and mathematical operations on floating-point numbers performed by the CPU’s floating-point unit (FPU).

 

Control unit:

The control unit of the CPU contains circuitry that uses electrical signals to direct the entire computer system to carry out stored program instructions. The control unit does not execute program instructions; rather, it directs other parts of the system to do so. The control unit communicates with both the ALU and memory.

Arithmetic logic unit:

The arithmetic logic unit (ALU) is a digital circuit within the processor that performs integer arithmetic and bitwise logic operations. The inputs to the ALU are the data words to be operated on (called operands), status information from previous operations, and a code from the control unit indicating which operation to perform. Depending on the instruction being executed, the operands may come from internal CPU registers or external memory, or they may be constants generated by the ALU itself.

When all input signals have settled and propagated through the ALU circuitry, the result of the performed operation appears at the ALU’s outputs. The result consists of both a data word, which may be stored in a register or memory, and status information that is typically stored in a special, internal CPU register reserved for this purpose.

Processor: 

A processor is an important part of a computer architecture without which you will not be able to perform anything on your computer. It is a programmable device that takes in input perform some arithmetic and logical operations over it and produce desired output. In simple words, a processor is a digital device on a chip which can fetch instruction from memory, decode and execute them and give results.

Basics of processor –
A processor takes a bunch of instructions in machine language and executes them, telling the processor what it has to do. processor performs three basic things while executing the instruction:

1.     It performs some basic operations like addition, subtraction, multiplication, division and some logical operations using its Arithmetic and Logical Unit (ALU). New processors also perform operations on floating point numbers also.

2.     Data in processor can move from one location to another.

3.     It has a Program Counter (PC) register that stores the address of next instruction based on the value of PC, processor jumps from one location to another and takes decision.

A typical processor structure looks like this.

Clock Speed of different processor:

· 16-bit processor –

·        8086: 4.7MHz, 8MHz, 10MHz

·         

·        8088: more than 5MHz

·         

·        80186/80188: 6MHz

·         

80286: 8MHz

 

· 32-bit processor –

·        INTEL 80386: 16MHz to 33MHz

·         

·        INTEL 80486: 16MHz to 100MHz

·         

PENTIUM: 66MHz

· 64-bit processor –

·        INTEL CORE-2: 1.2GHz to 3GHz

·         

·        INTEL i7: 66GHz to 3.33GHz

·         

·        INTEL i5: 2.4GHz to 3.6GHz

·         

INTEL i3: 2.93GHz to 3.33GHz

We do not have any 128-bit processor in work at present one among the reasons for this is that we are a long way from exhausting the 64-bit address space itself, we use it a constant rate of roughly 2 bits every 3 years. At present we have only used 48 bits of 64 bits so why require 128-bit address space. Also 128-bit processor would be much slower than the 64-bit processor.

Complex Instruction Set Computer (CISC) –
CISC or Complex Instruction Set Computer is a computer architecture where instructions are such that a single instruction can execute multiple low-level operations like loading from memory, storing into memory or an arithmetic operation etc. It has multiple addressing nodes within single instruction. CISC makes use of very few registers.

 

1. Intel 386

2. Intel 486

3. Pentium

4. Pentium Pro

5. Pentium II

6. Pentium III

7. Motorola 68000

8. Motorola 68020

9. Motorola 68040 etc.

· Reduced Instruction Set Computer (RISC) –
RISC or Reduced Instruction Set Computer is a computer architecture where instruction is simple and designed to get executed quickly. Instructions get completed in one clock cycle this is because of the optimization of instructions and pipelining (a technique that allows for simultaneous execution of parts, or stages, of instructions to more efficiently process instructions). RISC makes use of multiple registers to avoid large interactions with memory. It has few addressing nodes.

1. IBM RS6000

2. MC88100

3. DEC Alpha 21064

4. DEC Alpha 21164

5. DEC Alpha 21264

· Explicitly Parallel Instruction Computing (EPIC) –
EPIC or Explicitly Parallel Instruction Computing permits computer to execute instructions parallel using compilers. It allows complex instructions execution without using higher clock frequencies. EPIC encodes its instruction into 128-bit bundles. Each bundle contains three instructions which are encoded in 41 bits each and a 5-bit template field (contains information about types of instructions in bundle and which instructions can be executed in parallel)

Decode:

The instruction that the CPU fetches from memory determines what the CPU will do. In the decode step, performed by the circuitry known as the instruction decoder, the instruction is converted into signals that control other parts of the CPU.

The way in which the instruction is interpreted is defined by the CPU’s instruction set architecture (ISA). Often, one group of bits (that is, a “field”) within the instruction, called the opcode, indicates which operation is to be performed, while the remaining fields usually provide supplemental information required for the operation, such as the operands. Those operands may be specified as a constant value (called an immediate value), or as the location of a value that may be a processor register or a memory address, as determined by some addressing mode.

Integer range:

Every CPU represents numerical values in a specific way. For example, some early digital computers represented numbers as familiar decimal (base 10) numeral system values, and others have employed more unusual representations such as ternary (base three). Nearly all modern CPUs represent numbers in binary form, with each digit being represented by some two-valued physical quantity such as a “high” or “low” voltage.

A six-bit word containing the binary encoded representation of decimal value 40. Most modern CPUs employ word sizes that are a power of two, for example eight, 16, 32 or 64 bits.

Related to numeric representation is the size and precision of integer numbers that a CPU can represent. In the case of a binary CPU, this is measured by the number of bits (significant digits of a binary encoded integer) that the CPU can process in one operation, which is commonly called “word size”, “bit width”, “data path width”, “integer precision”, or “integer size”. A CPU’s integer size determines the range of integer values it can directly operate on. For example, an 8-bit CPU can directly manipulate integers represented by eight bits, which have a range of 256 (2⁸) discrete integer values.

Integer range can also affect the number of memory locations the CPU can directly address (an address is an integer value representing a specific memory location). For example, if a binary CPU uses 32 bits to represent a memory address then it can directly address 2³² memory locations. To circumvent this limitation and for various other reasons, some CPUs use mechanisms (such as bank switching) that allow additional memory to be addressed.

CPUs with larger word sizes require more circuitry and consequently are physically larger, cost more, and consume more power (and therefore generate more heat). As a result, smaller 4- or 8-bit microcontrollers are commonly used in modern applications even though CPUs with much larger word sizes (such as 16, 32, 64, even 128-bit) are available. When higher performance is required, however, the benefits of a larger word size (larger data ranges and address spaces) may outweigh the disadvantages.

To gain some of the advantages afforded by both lower and higher bit lengths, many CPUs are designed with different bit widths for different portions of the device. For example, the IBM System/370 used a CPU that was primarily 32 bit, but it used 128-bit precision inside its floating point units to facilitate greater accuracy and range in floating point numbers. Many later CPU designs use similar mixed bit width, especially when the processor is meant for general-purpose usage where a reasonable balance of integer and floating point capability is required.

 

 

Clock rate:

Most CPUs are synchronous circuits, which means they employ a clock signal to pace their sequential operations. The clock signal is produced by an external oscillator circuit that generates a consistent number of pulses each second in the form of a periodic square wave. The frequency of the clock pulses determines the rate at which a CPU executes instructions and, consequently, the faster the clock, the more instructions the CPU will execute each second.

To ensure proper operation of the CPU, the clock period is longer than the maximum time needed for all signals to propagate (move) through the CPU. In setting the clock period to a value well above the worst-case propagation delay, it is possible to design the entire CPU and the way it moves data around the “edges” of the rising and falling clock signal. This has the advantage of simplifying the CPU significantly, both from a design perspective and a component-count perspective. However, it also carries the disadvantage that the entire CPU must wait on its slowest elements, even though some portions of it are much faster. This limitation has largely been compensated for by various methods of increasing CPU parallelism (see below).

However, architectural improvements alone do not solve all of the drawbacks of globally synchronous CPUs. For example, a clock signal is subject to the delays of any other electrical signal. Higher clock rates in increasingly complex CPUs make it more difficult to keep the clock signal in phase (synchronized) throughout the entire unit. This has led many modern CPUs to require multiple identical clock signals to be provided to avoid delaying a single signal significantly enough to cause the CPU to malfunction. Another major issue, as clock rates increase dramatically, is the amount of heat that is dissipated by the CPU. The constantly changing clock causes many components to switch regardless of whether they are being used at that time. In general, a component that is switching uses more energy than an element in a static state. Therefore, as clock rate increases, so does energy consumption, causing the CPU to require more heat dissipation in the form of CPU cooling solutions.

Rather than totally removing the clock signal, some CPU designs allow certain portions of the device to be asynchronous, such as using asynchronous ALUs in conjunction with superscalar pipelining to achieve some arithmetic performance gains. While it is not altogether clear whether totally asynchronous designs can perform at a comparable or better level than their synchronous counterparts, it is evident that they do at least excel in simpler math operations. This, combined with their excellent power consumption and heat dissipation properties, makes them very suitable for embedded computers.

Chipset:

In a computer system, a chipset is a set of electronic components in an integrated circuit that manages the data flow between the processor, memory and peripherals. It is usually found on the motherboard. Chipsets are usually designed to work with a specific family of microprocessors. Because it controls communications between the processor and external devices, the chipset plays a crucial role in determining system performance.

Random Access Memory:

Example of writable volatile random-access memory: Synchronous Dynamic RAM modules, primarily used as main memory in personal computers, workstations, and servers.

Random-access memory (RAM): is a form of computer data storage. A random-access memory device allows data items to be accessed (read or written) in almost the same amount of time irrespective of the physical location of data inside the memory. In contrast, with other direct-access data storage media such as hard disks, CD-RWs, DVD-RWs and the older drum memory, the time required to read and write data items varies significantly depending on their physical locations on the recording medium, due to mechanical limitations such as media rotation speeds and arm movement delays.

Today, random-access memory takes the form of integrated circuits. RAM is normally associated with volatile types of memory (such as DRAM memory modules), where stored information is lost if power is removed, although many efforts have been made to develop non-volatile RAM chips. Other types of non-volatile memory exist that allow random access for read operations, but either do not allow write operations or have limitations on them. These include most types of ROM and a type of flash memory called NOR-Flash.

 

Types of RAM:

The two main forms of modern RAM are static RAM (SRAM) and dynamic RAM (DRAM). In SRAM, a bit of data is stored using the state of a six-transistor memory cell. This form of RAM is more expensive to produce, but is generally faster and requires less power than DRAM and, in modern computers, is often used as cache memory for the CPU. DRAM stores a bit of data using a transistor and capacitor pair, which together comprise a DRAM memory cell. The capacitor holds a high or low charge (1 or 0, respectively), and the transistor acts as a switch that lets the control circuitry on the chip read the capacitor’s state of charge or change it. As this form of memory is less expensive to produce than static RAM, it is the predominant form of computer memory used in modern computers.

Both static and dynamic RAM are considered volatile, as their state is lost or reset when power is removed from the system. By contrast, read-only memory (ROM) stores data by permanently enabling or disabling selected transistors, such that the memory cannot be altered. Writeable variants of ROM (such as EEPROM and flash memory) share properties of both ROM and RAM, enabling data to persist without power and to be updated without requiring special equipment. These persistent forms of semiconductor ROM include USB flash drives, memory cards for cameras and portable devices, etc. ECC memory (which can be either SRAM or DRAM) includes special circuitry to detect and/or correct random faults (memory errors) in the stored data, using parity bits or error correction code.

In general, the term RAM refers solely to solid-state memory devices (either DRAM or SRAM), and more specifically the main memory in most computers. In optical storage, the term DVD-RAM is somewhat of a misnomer since, unlike CD-RW or DVD-RW it does not need to be erased before reuse. Nevertheless, a DVD-RAM behaves much like a hard disc drive if somewhat slower.

Memory hierarchy:

One can read and over-write data in RAM. Many computer systems have a memory hierarchy consisting of processor registers, on-die SRAM caches, external caches, DRAM, paging systems and virtual memory or swap space on a hard drive. This entire pool of memory may be referred to as “RAM” by many developers, even though the various subsystems can have very different access times, violating the original concept behind the random-access term in RAM. Even within a hierarchy level such as DRAM, the specific row, column, bank, rank, channel, or interleave organization of the components make the access time variable, although not to the extent that rotating storage media or a tape is variable. The overall goal of using a memory hierarchy is to obtain the higher possible average access performance while minimizing the total cost of the entire memory system (generally, the memory hierarchy follows the access time with the fast CPU registers at the top and the slow hard drive at the bottom).

In many modern personal computers, the RAM comes in an easily upgraded form of modules called memory modules or DRAM modules about the size of a few sticks of chewing gum. These can quickly be replaced should they become damaged or when changing needs demand more storage capacity. As suggested above, smaller amounts of RAM (mostly SRAM) are also integrated in the CPU and other ICs on the motherboard, as well as in hard-drives, CD-ROMs, and several other parts of the computer system.

Other uses of RAM:

In addition to serving as temporary storage and working space for the operating system and applications, RAM is used in numerous other ways.

Virtual memory:

Most modern operating systems employ a method of extending RAM capacity, known as “virtual memory”. A portion of the computer’s hard drive is set aside for a paging file or a scratch partition, and the combination of physical RAM and the paging file form the system’s total memory. (For example, if a computer has 2 GB of RAM and a 1 GB page file, the operating system has 3 GB total memory available to it.) When the system runs low on physical memory, it can “swap” portions of RAM to the paging file to make room for new data, as well as to read previously swapped information back into RAM. Excessive use of this mechanism results in thrashing and generally hampers overall system performance, mainly because hard drives are far slower than RAM.

RAM disk:

Software can “partition” a portion of a computer’s RAM, allowing it to act as a much faster hard drive that is called a RAM disk. A RAM disk loses the stored data when the computer is shut down, unless memory is arranged to have a standby battery source.

Shadow RAM:

Sometimes, the contents of a relatively slow ROM chip are copied to read/write memory to allow for shorter access times. The ROM chip is then disabled while the initialized memory locations are switched in on the same block of addresses (often write-protected). This process, sometimes called shadowing, is fairly common in both computers and embedded systems.

As a common example, the BIOS in typical personal computers often has an option called “use shadow BIOS” or similar. When enabled, functions relying on data from the BIOS’s ROM will instead use DRAM locations (most can also toggle shadowing of video card ROM or other ROM sections). Depending on the system, this may not result in increased performance, and may cause incompatibilities. For example, some hardware may be inaccessible to the operating system if shadow RAM is used. On some systems the benefit may be hypothetical because the BIOS is not used after booting in favor of direct hardware access. Free memory is reduced by the size of the shadowed ROMs.

Recent developments:

Several new types of non-volatile RAM, which will preserve data while powered down, are under development. The technologies used include carbon nanotubes and approaches utilizing Tunnel magnetoresistance. Amongst the 1st generation MRAM, a 128 KiB (128 × 2¹⁰ bytes) chip was manufactured with 0.18 µm technology in the summer of 2003. In June 2004, Infineon Technologies unveiled a 16 MiLB (16 × 2²⁰ bytes) prototype again based on 0.18 µm technology. There are two 2nd generation techniques currently in development: thermal-assisted switching (TAS) which is being developed by Crocus Technology, and spin-transfer torque (STT) on which Crocus, Hynix, IBM, and several other companies are working. Nanterre built a functioning carbon nanotube memory prototype 10 Gibb (10 × 2³⁰ bytes) array in 2004. Whether some of these technologies will be able to eventually take a significant market share from either DRAM, SRAM, or flash-memory technology, however, remains to be seen.

Since 2006, “solid-state drives” (based on flash memory) with capacities exceeding 256 gigabytes and performance far exceeding traditional disks have become available. This development has started to blur the definition between traditional random-access memory and “disks”, dramatically reducing the difference in performance.

Some kinds of random-access memory, such as “Eco RAM”, are specifically designed for server farms, where low power consumption is more important than speed.

 

 

Hard Disk Drives (HDD): known as non-volatile RAM in the IT Industry (as are flash drives, USB pens etc.), is where your operating system files are stored. Most people also store their documents here (remember to back up!), although cloud storage is becoming more popular.

When your machine is switched off, your O/S and data files remain on the hard drive for the next time you switch back on.

There are lots of different types and sizes of HDD's available today, all with different performances and capabilities. An increasingly common type is the solid state drive. 

When you double clink your document to open, the data is read and loaded into RAM. When you save your document, all your changes are written back to your hard drive.

Read-Only Memory:

Read-only memory (ROM) is a class of storage medium used in computers and other electronic devices. Data stored in ROM can only be modified slowly, with difficulty, or not at all, so it is mainly used to distribute firmware (software that is very closely tied to specific hardware, and unlikely to need frequent updates).

Strictly, read-only memory refers to memory that is hard-wired, such as diode matrix and the later mask ROM. Although discrete circuits can be altered (in principle), integrated circuits (ICs) cannot and are useless if the data is bad. The fact that such memory can never be changed is a large drawback; more recently, ROM commonly refers to memory that is read-only in normal operation, while reserving the fact of some possible way to change it.

Other types of non-volatile memory such as erasable programmable read only memory (EPROM) and electrically erasable programmable read-only memory (EEPROM or Flash ROM) are sometimes referred to, in an abbreviated way, as “read-only memory” (ROM); although these types of memory can be erased and re-programmed multiple times, writing to this memory takes longer and may require different procedures than reading the memory. When used in this less precise way, “ROM” indicates anon-volatile memory which serves functions typically provided by mask ROM, such as storage of program code and nonvolatile data.

Bus:

4 PCI Express bus card slots (from top to bottom: x4, x16, x1 and x16), compared to a 32-bit conventional PCI bus card slot (very bottom)

In computer architecture, a bus (related to the Latin “omnibus”, meaning “for all”) is a communication system that transfers data between components inside a computer, or between computers. This expression covers all related hardware components (wire, optical fiber, etc.) and software, including communication protocols.

Early computer buses were parallel electrical wires with multiple connections, but the term is now used for any physical arrangement that provides the same logical functionality as a parallel electrical bus. Modern computer buses can use both parallel and bit serial connections, and can be wired in either a multidrop (electrical parallel) or daisy chain topology, or connected by switched hubs, as in the case of USB.

Background and nomenclature

Computer systems generally consist of three main parts: the central processing unit (CPU) that processes data, memory that holds the programs and data to be processed, and I/O (input/output) devices as peripherals that communicate with the outside world. An early computer might use a hand-wired CPU of vacuum tubes, a magnetic drum for main memory, and a punch tape and printer for reading and writing data. In a modern system we might find a multi-core CPU, DDR3 SDRAM for memory, a hard drive for secondary storage, a graphics card and LCD display as a display system, a mouse and keyboard for interaction, and a Wi-Fi connection for networking. In both examples, computer buses of one form or another move data between all of these devices.

In most traditional computer architectures, the CPU and main memory tend to be tightly coupled. A microprocessor conventionally is a single chip which has a number of electrical connections on its pins that can be used to select an “address” in the main memory and another set of pins to read and write the data stored at that location. In most cases, the CPU and memory share signalling characteristics and operate in synchrony. The bus connecting the CPU and memory is one of the defining characteristics of the system, and often referred to simply as the system bus.

It is possible to allow peripherals to communicate with memory in the same fashion, attaching adaptors in the form of expansion cards directly to the system bus. This is commonly accomplished through some sort of standardized electrical connector, several of these forming the expansion bus or local bus. However, as the performance differences between the CPU and peripherals varies widely, some solution is generally needed to ensure that peripherals do not slow overall system performance. Many CPUs feature a second set of pins similar to those for communicating with memory, but able to operate at very different speeds and using different protocols. Others use smart controllers to place the data directly in memory, a concept known as direct memory access. Most modern systems combine both solutions, where appropriate.

As the number of potential peripherals grew, using an expansion card for every peripheral became increasingly untenable. This has led to the introduction of bus systems designed specifically to support multiple peripherals. Common examples are the SATA ports in modern computers, which allow a number of hard drives to be connected without the need for a card. However, these high-performance systems are generally too expensive to implement in low-end devices, like a mouse. This has led to the parallel development of a number of low-performance bus systems for these solutions, the most common example being Universal Serial Bus. All such examples may be referred to as peripheral buses, although this terminology is not universal.

In modern systems the performance difference between the CPU and main memory has grown so great that increasing amounts of high-speed memory is built directly into the CPU, known as a cache. In such systems, CPUs communicate using high-performance buses that operate at speeds much greater than memory, and communicate with memory using protocols similar to those used solely for peripherals in the past. These system buses are also used to communicate with most (or all) other peripherals, through adaptors, which in turn talk to other peripherals and controllers. Such systems are architecturally more similar to multicomputer, communicating over a bus rather than a network. In these cases, expansion buses are entirely separate and no longer share any architecture with their host CPU (and may in fact support many different CPUs, as is the case with PCI). What would have formerly been a system bus is now often known as a front-side bus.

Given these changes, the classical terms “system”, “expansion” and “peripheral” no longer have the same connotations. Other common categorization systems are based on the buses primary role, connecting devices internally or externally, PCI vs. SCSI for instance. However, many common modern bus systems can be used for both; SATA and the associated SATA are one example of a system that would formerly be described as internal.

Internal bus:

The internal bus, also known as internal data bus, memory bus, system bus or Front-Side-Bus, connects all the internal components of a computer, such as CPU and memory, to the motherboard. Internal data buses are also referred to as a local bus, because they are intended to connect to local devices. This bus is typically rather quick and is independent of the rest of the computer operations.

External bus:

The external bus, or expansion bus, is made up of the electronic pathways that connect the different external devices, such as printer etc., to the computer.

Implementation details:

Buses can be parallel buses, which carry data words in parallel on multiple wires, or serial buses, which carry data in bit-serial form. The addition of extra power and control connections, differential drivers, and data connections in each direction usually means that most serial buses have more conductors than the minimum of one used in 1-Wire and UNI/O. As data rates increase, the problems of timing skew, power consumption, electromagnetic interference and crosstalk across parallel buses become more and more difficult to circumvent. One partial solution to this problem has been to double pump the bus. Often, a serial bus can be operated at higher overall data rates than a parallel bus, despite having fewer electrical connections, because a serial bus inherently has no timing skew or crosstalk. USB, FireWire, and Serial ATA are examples of this. Multidrop connections do not work well for fast serial buses, so most modern serial buses use daisy-chain or hub designs.

Network connections such as Ethernet are not generally regarded as buses, although the difference is largely conceptual rather than practical. An attribute generally used to characterize a bus is that power is provided by the bus for the connected hardware. This emphasizes the busbar origins of bus architecture as supplying switched or distributed power. This excludes, as buses, schemes such as serial RS-232, parallel Centronics, IEEE 1284 interfaces and Ethernet, since these devices also needed separate power supplies. Universal Serial Bus devices may use the bus supplied power, but often use a separate power source. This distinction is exemplified by a telephone system with a connected modem, where the RJ11 connection and associated modulated signaling scheme is not considered a bus, and is analogous to an Ethernet connection. A phone line connection scheme is not considered to be a bus with respect to signals, but the Central Office uses buses with cross-bar switches for connections between phones.

However, this distinction—​that power is provided by the bus—​is not the case in many avionic systems, where data connections such as ARINC 429, ARINC 629, MIL-STD-1553B (STANAG 3838), and EFA Bus (STANAG 3910) are commonly referred to as “data buses” or, sometimes, “databases”. Such avionic data buses are usually characterized by having several equipment’s or Line Replaceable Items/Units (LRI/LRUs) connected to a common, shared media. They may, as with ARINC 429, be simplex, i.e. have a single source LRI/LRU or, as with ARINC 629, MIL-STD-1553B, and STANAG 3910, be duplex, allow all the connected LRI/LRUs to act, at different times (half duplex), as transmitters and receivers of data.

First generation:

Early computer buses were bundles of wire that attached computer memory and peripherals. Anecdotally termed the “digit trunk “, they were named after electrical power buses, or busbars. Almost always, there was one bus for memory, and one or more separate buses for peripherals. These were accessed by separate instructions, with completely different timings and protocols.

One of the first complications was the use of interrupts. Early computer programs performed I/O by waiting in a loop for the peripheral to become ready. This was a waste of time for programs that had other tasks to do. Also, if the program attempted to perform those other tasks, it might take too long for the program to check again, resulting in loss of data. Engineers thus arranged for the peripherals to interrupt the CPU. The interrupts had to be prioritized, because the CPU can only execute code for one peripheral at a time, and some devices are more time-critical than others.

High-end systems introduced the idea of channel controllers, which were essentially small computers dedicated to handling the input and output of a given bus. IBM introduced these on the IBM 709 in 1958, and they became a common feature of their platforms. Other high-performance vendors like Control Data Corporation implemented similar designs. Generally, the channel controllers would do their best to run all of the bus operations internally, moving data when the CPU was known to be busy elsewhere if possible, and only using interrupts when necessary. This greatly reduced CPU load, and provided better overall system performance.

Single system bus

To provide modularity, memory and I/O buses can be combined into a unified system bus. In this case, a single mechanical and electrical system can be used to connect together many of the system components, or in some cases, all of them.

Later computer programs began to share memory common to several CPUs. Access to this memory bus had to be prioritized, as well. The simple way to prioritize interrupts or bus access was with a daisy chain. In this case signals will naturally flow through the bus in physical or logical order, eliminating the need for complex scheduling.

Minis and micros

Digital Equipment Corporation (DEC) further reduced cost for mass-produced minicomputers, and mapped peripherals into the memory bus, so that the input and output devices appeared to be memory locations. This was implemented in the Uni-bus of the PDP-11 around 1969.

Early microcomputer bus systems were essentially a passive backplane connected directly or through buffer amplifiers to the pins of the CPU. Memory and other devices would be added to the bus using the same address and data pins as the CPU itself used, connected in parallel. Communication was controlled by the CPU, which had read and written data from the devices as if they are blocks of memory, using the same instructions, all timed by a central clock controlling the speed of the CPU. Still, devices interrupted the CPU by signaling on separate CPU pins. For instance, a disk drive controller would signal the CPU that new data was ready to be read, at which point the CPU would move the data by reading the “memory location” that corresponded to the disk drive. Almost all early microcomputers were built in this fashion, starting with the S-100 bus in the Altair 8800 computer system.

In some instances, most notably in the IBM PC, although similar physical architecture can be employed, instructions to access peripherals (in and out) and memory (mov and others) have not been made uniform at all, and still generate distinct CPU signals, that could be used to implement a separate I/O bus.

These simple bus systems had a serious drawback when used for general-purpose computers. All the equipment on the bus has to talk at the same speed, as it shared a single clock.

Increasing the speed of the CPU becomes harder, because the speed of all the devices must increase as well. When it is not practical or economical to have all devices as fast as the CPU, the CPU must either enter a wait state, or work at a slower clock frequency temporarily, to talk to other devices in the computer. While acceptable in embedded systems, this problem was not tolerated for long in general-purpose, user-expandable computers.

Such bus systems are also difficult to configure when constructed from common off-the-shelf equipment. Typically, each added expansion card requires many jumpers in order to set memory addresses, I/O addresses, interrupt priorities, and interrupt numbers.

Second generation

“Second generation” bus systems like Nu-Bus addressed some of these problems. They typically separated the computer into two “worlds”, the CPU and memory on one side, and the various devices on the other. A bus controller accepted data from the CPU side to be moved to the peripherals side, thus shifting the communications protocol burden from the CPU itself. This allowed the CPU and memory side to evolve separately from the device bus, or just “bus”. Devices on the bus could talk to each other with no CPU intervention. This led to much better “real world” performance, but also required the cards to be much more complex. These buses also often addressed speed issues by being “bigger” in terms of the size of the data path, moving from 8-bit parallel buses in the first generation, to 16 or 32-bit in the second, as well as adding software setup (now standardized as Plug-n-play) to supplant or replace the jumpers.

However, these newer systems shared one quality with their earlier cousins, in that everyone on the bus had to talk at the same speed. While the CPU was now isolated and could increase speed, CPUs and memory continued to increase in speed much faster than the buses they talked to. The result was that the bus speeds were now very much slower than what a modern system needed, and the machines were left starved for data. A particularly common example of this problem was that video cards quickly outran even the newer bus systems like PCI, and computers began to include AGP just to drive the video card. By 2004 AGP was outgrown again by high-end video cards and other peripherals and has been replaced by the new PCI Express bus.

An increasing number of external devices started employing their own bus systems as well. When disk drives were first introduced, they would be added to the machine with a card plugged into the bus, which is why computers have so many slots on the bus. But through the 1980s and 1990s, new systems like SCSI and IDE were introduced to serve this need, leaving most slots in modern systems empty. Today there are likely to be about five different buses in the typical machine, supporting various devices.

Third generation

“Third generation” buses have been emerging into the market since about 2001, including Hyper Transport and InfiniBand. They also tend to be very flexible in terms of their physical connections, allowing them to be used both as internal buses, as well as connecting different machines together. This can lead to complex problems when trying to service different requests, so much of the work on these systems concerns software design, as opposed to the hardware itself. In general, these third-generation buses tend to look more like a network than the original concept of a bus, with a higher protocol overhead needed than early systems, while also allowing multiple devices to use the bus at once.

Buses such as Wishbone have been developed by the open source hardware movement in an attempt to further remove legal and patent constraints from computer design.

Networking:

A network consists of two or more computers that are linked in order to share resources (such as printers and CDs), exchange files, or allow electronic communications. The computers on a network may be linked through cables, telephone lines, radio waves, satellites, or infrared light beams.

Different Types of Network:

The size of the Network can vary from connecting two computers inside a small room to lakhs of computers across the world. Different types of networks are.

1. Personal Area Network (PAN)

• Deployed mainly in a home environment, connecting one or more computers, printers, phones, other personal gadgets through modem either in wired or wireless mode.
• It serves the purpose of sharing documents & photos within nodes, accessing internet and entertainment.

2. Local Area Network (LAN)

• LAN connects computers and other equipment within a premise or building and it enables local users to share information through file servers, print documents thru centralized printers, do transactions through central servers and connect to outside networks in a secured manner through a firewall, routers.
• Computers and devices are connected through Hub, switches, network adapters, cables, and optic fibers. In modern LAN, computers are connected in wireless mode thru access points (Antenna) and it provides the flexible seating arrangement and freedom to millennials to work from anywhere within the office.
• LAN provides a high-speed network, optimizes the software licenses usage and saves cost by connecting the entire users through a single internet connection & sharing the resources effectively.
• A LAN can be logically split into multiple Virtual local area networks (VLANs) and they are connected through a router. Each VLAN will have its own characteristics and access can be restricted across VLANs for users.

 

 

3. Metropolitan Area Network (MAN)

• MAN integrates multiple LANs within a metro city into a bigger network. Optical fibers and Cables are the medium of MAN and it supports a distributed application environment. Information and resources can be shared across MAN by the users and the access can be restricted as required.
• MAN provides a platform for Organizations to plan their near-disaster recovery (Near DR) center in one of their facilities within the city, as a backup for critical enterprise applications. These near DR can work in synchronized data replication mode, which has zero data loss in case of switch over to DR during emergencies in the primary data center.
• Campus area network (CAN) is another version of the Metro network, widely used in a vast university campus. Each department can have its own LAN and they can be connected through CAN and students can share resources across these networks. MAN provides a solid backbone for building the Wide area network.

4. Wide Area Network (WAN)

• WAN links multiple LAN and MAN spread across a wide geography, into a secured single large network. It covers vast regions across a country and outside. WAN connect routers of individual LAN/MAN through the public leased line, MPLS and satellite connectivity.
• An Organization with multi-location manufacturing/marketing facilities can have one network and centralize the data center operation in a primary site and host the application over the WAN. Users can log in to the system from any location within the network and access centralized ERP seamlessly and share the resources efficiently.

5. Storage Area Network (SAN)

• SAN is an exclusive network connecting storage with servers. Storage devices are pooled together within the data center and they are shared with multiple servers for accessing data.
• An exclusive Ethernet/fiber channel network connecting storage with a server through protocols like serially attached Small computer system interface (SCSI), Fiber channel and internet SCSI (iSCSI), provide the high performance required in data storage/retrievals.

 

 

6. System Area Network

In a system area network, Servers are clustered through high-speed networks in a local environment and offered as consolidated computing power for power-intensive applications.

7. Enterprise Private Network (EPN)

EPN is built by businesses by connecting all the computers and devices across all the departments for the purpose of data exchange. This network manages all the operating systems of devices and communication protocols and provides a secured connection.

8. Virtual Private Network (VPN)

Virtual Private Network (VPN) offers the best of both the world experience for online users by providing them the security of the local networks while accessing the public internet. In VPN, a private secured tunnel enables users to access the internet in a protected way as they work in their own network. Users access VPN servers through client software installed in their Desktop/Laptop/Tab/ Mobile devices. Client software sends the data to the VPN server in an encrypted way, masking the identity of the users and the VPN server, in turn, routes the data to the final online destination in a secure way.

9. Internet

Internet is a network of all networks connected through Routers, gateways, and bridges using Internet protocols. Users connect to the internet through Browsers using URL and get the information they want.

Advantages and Disadvantages of Networks

Some of the advantages and disadvantages of networks are given below:

Advantages:

• Enables centralized applications hosting/data storage and users accessing it through LAN, MAN, WAN in a secure way.
• Results in considerable cost saving thro centralized administration.
• Provides Real-time information to users.
• Ensures data integrity.
• Enables business transactions, net banking, across any geography.
• Optimizes software license usage and resource utilization.
• Provides a collaboration platform for employees and reduces travel cost.

 

Disadvantages

• Vulnerability to cyber-attacks due to the exposure of network to the outside world.
• Set up cost is huge.
• Sensitive Data need to be encrypted and protected through the firewall.
• The administration of networks poses a challenge due to its size and spread.

 

IP Addresses

An IP (Internet Protocol) address is a numerical label assigned to the devices connected to a computer network that uses the IP for communication.

IP address act as an identifier for a specific machine on a particular network. It also helps you to develop a virtual connection between a destination and a source. The IP address is also called IP number or internet address. It helps you to specify the technical format of the addressing and packets scheme. Most networks combine TCP with IP.

Types of IP address

There are mainly four types of IP addresses:

• Public,
• Private,
• Static
• Dynamic.

Among them, public and private addresses are based on their location of the network private, which should be used inside a network while the public IP is used outside of a network.

Let us see all these types of IP address in detail.

 

 

Public IP Addresses

A public IP address is an address where one primary address is associated with your whole network. In this type of IP address, each of the connected devices has the same IP address.

This type of public IP address is provided to your router by your ISP.

 

 

Private IP Addresses

A private IP address is a unique IP number assigned to every device that connects to your home internet network, which includes devices like computers, tablets, smartphones, which is used in your household.

It also likely includes all types of Bluetooth devices you use, like printers or printers, smart devices like TV, etc. With a rising industry of internet of things (IoT) products, the number of private IP addresses you are likely to have in your own home is growing.

Dynamic IP address:

Dynamic IP addresses always keep changing. It is temporary and are allocated to a device every time it connects to the web. Dynamic IPs can trace their origin to a collection of IP addresses that are shared across many computers.

Dynamic IP addresses are another important type of internet protocol address. It is active for a specific amount of time; after that, it will expire.

Static IP Addresses

A static IP address is an IP address that cannot be changed. In contrast, a dynamic IP address will be assigned by a Dynamic Host Configuration Protocol (DHCP) server, which is subject to change. Static IP address never changes, but it can be altered as part of routine network administration.

Static IP addresses are consistent, which is assigned once, that stays the same over the years. This type of IP also helps you procure a lot of information about a device.

 

Types of Website IP Addresses

Two types of website IP Addresses are 1) Share IP Address 2) Dedicated IP Address

Shared IP Addresses:

Shared IP address is used by small business websites that do not yet get many visitors or have many files or pages on their site. The IP address is not unique and it is shared with other websites.

Dedicated IP Addresses:

Dedicated IP address is assigned uniquely to each website. Dedicated IP addresses helps you avoid any potential backlists because of bad behavior from others on your server. The dedicated IP address also gives you the option of pulling up your website using the IP address alone, instead of your domain name. It also helps you to access your website when you are waiting on a domain transfer.

Version of IP address

Two types of IP addresses are

1)IPV4   and   2) IPV6.

IP Version 6

The IPv6 is the most recent version of Internet Protocol. As the Internet is growing rapidly, there is a global shortage for IPv4. IPv6 was developed by the Internet Engineering Task Force (IETF). IPv6 is intended to replace the IPv4. IPv6 uses a 128-bit address and it allows 2128 i.e. approximately 3.4×1038 addresses. The actual number is slightly smaller as some ranges are reserved for special use or not used. The IPv6 addresses are represented by 8 groups of four hexadecimal digits with the groups being supported by colons. An example is given below: 

The features of IPv6

The main features of the IPv6 are listed below.

1) IPv6 provides better end-to-end connectivity than IPv4.

2) Comparatively faster routing.

3) IPv6 offers ease of administration than IPv4.

4) More security for applications and networks.

5) It provides better Multicast and Anycast abilities.

6) Better mobility features than IPv4.

7) IPv6 follows the key design principles of IPv4 and so that the transition from IPv4 to IPv6 is smoother.

These are the key features of the IPv6 when compared to the IPv4. However, IPv6 has not become popular as IPv4.

 

 

IP Version 4

IP Version 4 (IPv4) was defined in 1981. It has not undergone much changes from that time. Unfortunately, there is a need of IP addresses more than IPv4 could supply.

IPv4 uses 32-bit IP address. So, the maximum number of IP address is 2³²—or 4,294,967,296.

This is a little more than four billion IP addresses. An IPv4 address is typically formatted as four 8-bit fields. Each 8-bit field represents a byte of the IPv4 address. As we have seen earlier, each fields will be separated with dots. This method of representing the byte of an IPv4 address is referred to as the dotted-decimal format. The bytes of the IPv4 is further classified into two parts. The network part and the host part.

Network Part:

This part specifies the unique number assigned to your network. It also identifies the class of network assigned. The network part takes two bytes of the IPv4 address.

 

 

Host Part:

This is the part of the IPv4 address that you can assign to each host. It uniquely identifies this machine on your network. For all hosts on your network, the network part of the IP address will be the same and host part will be changing.

IP address and classes:

The IP hierarchy contains many classes of the IP addresses. Broadly, the IPv4 addressing system is divided into five classes of IP address. All the five classes are identified by the first octet of the IP address.

The classes of IPv4 addresses:

The different classes of the IPv4 address are the following:

1) Class A address

2) Class B address

3) Class C address

4) Class D address

5) Class E address

Class	Address Range	Subnet masking	Example IP	Leading bits	Max number of networks	Application
IP Class A	1 to 126	255.0.0.0	1.1.1.1	8	128	Used for large number of hosts.
IP Class B	128 to 197	255.255.0.0	128.1.1.1	16	16384	Used for medium size network.
IP Class C	192 to 223	255.255.255.0	192.1.11.	24	2097157	Used for local area network.
IP Class D	224 to 239	NA	NA	NA	NA	Reserve for multi-tasking.
IP Class	240 to 254	NA	NA	NA	NA	This class is reserved for research and Development Purposes.

 

IP address work:

IP address works in an IP network like a postal address. For example, a postal address combines two addresses, address, or your area your house address. The address or your area is a group address of all houses that belong to a specific area. The house address is the unique address of your homes in that area. Here, your area is represented by a PIN code number. In this example, the network address comprises all hosts which belong to a specific network. The host address is the unique address of a particular host in that network.

 

Classful Addressing:

Classful addressing is a network addressing the Internet's architecture from 1981 till Classless Inter-Domain Routing was introduced in 1993.This addressing method divides the IP address into five separate classes based on four address bits. Here, classes A, B, C offers addresses for networks of three distinct network sizes. Class D is only used for multicast, and class E reserved exclusively for experimental purposes.

Let's see each of the network classes in detail:

Class A Network:

This IP address class is used when there are a large number of hosts. In a Class A type of network, the first 8 bits (also called the first octet) identify the network, and the remaining have 24 bits for the host into that network.

An example of a Class A address is 102.168.212.226. Here, "102" helps you identify the network and 168.212.226 identify the host.

Class A addresses 127.0.0.0 to 127.255.255.255 cannot be used and is reserved for loopback and diagnostic functions.

Class B Network:

In a B class IP address, the binary addresses start with 10. In this IP address, the class decimal number that can be between 128 to 191. The number 127 is reserved for loopback, which is used for internal testing on the local machine. The first 16 bits (known as two octets) help you identify the network. The other remaining 16 bits indicate the host within the network.

An example of Class B IP address is 168.212.226.204, where *168 212* identifies the network and *226.204* helps you identify the Hut network host.

Class C Network:

Class C is a type of IP address that is used for the small network. In this class, three octets are used to indent the network. This IP ranges between 192 to 223.

In this type of network addressing method, the first two bits are set to be 1, and the third bit is set to 0, which makes the first 24 bits of the address them and the remaining bit as the host address. Mostly local area network used Class C IP address to connect with the network.

Example for a Class C IP address: 192.168.178.1

 

 

 

Network Topology:

Network topologies describe the methods in which all the elements of a network are mapped. The topology term refers to both the physical and logical layout of a network.

Types of Networking Topologies:

Two main types of networking topologies are 1) Physical topology 2) Logical topology.

Physical topology:

This type of network is an actual layout of the computer cables and other network devices

Logical topology:

Logical topology gives insight's about network's physical design.

Different types of Physical Topologies are:

• P2P Topology
• Bus Topology
• Ring Topology
• Star Topology
• Tree Topology
• Mesh Topology
• Hybrid Topology

Point to Point:

Point-to-point topology is the easiest of all the network topologies. In this method, the network consists of a direct link between two computers.

Bus Topology:

Bus topology uses a single cable which connects all the included nodes. The main cable acts as a spine for the entire network. One of the computers in the network acts as the computer server. When it has two endpoints, it is known as a linear bus topology.

Ring Topology:

In a ring network, every device has exactly two neighboring devices for communication purpose. It is called a ring topology as its formation is like a ring. In this topology, every computer is connected to another computer. Here, the last node is combined with a first one. This topology uses token to pass the information from one computer to another. In this topology, all the messages travel through a ring in the same direction.

Star Topology:

In the star topology, all the computers connect with the help of a hub. This cable is called a central node, and all other nodes are connected using this central node. It is most popular on LAN networks as they are inexpensive and easy to install.

Mesh Topology:

The mesh topology has a unique network design in which each computer on the network connects to every other. It is developing a P2P (point-to-point) connection between all the devices of the network. It offers a high level of redundancy, so even if one network cable fails, still data has an alternative path to reach its destination.

Tree Topology:

Tree topologies have a root node, and all other nodes are connected which form a hierarchy. So, it is also known as hierarchical topology. This topology integrates various star topologies together in a single bus, so it is known as a Star Bus topology. Tree topology is a very common network which is similar to a bus and star topology.

Hybrid Topology:

Hybrid topology combines two or more topologies. You can see in the above architecture in such a manner that the resulting network does not exhibit one of the standard topologies.

For example, as you can see in the above image that in an office in one department, Star and P2P topology is used. A hybrid topology is always produced when two different basic network topologies are connected.