Computer Hardware

The Motherboard AGP Expansion Slots

Accelerated Graphics Port (AGP) slots are becoming more popular. In the past, if you wanted to use a high-speed, accelerated 3D graphics video card, you had to install the card into an existing PCI or ISA slot. AGP slots were designed to be a direct connection between the video circuitry and the PC's memory. They are also easily recognizable, because they are usually brown, are located right next to the PCI slots on the motherboard, and are shorter than the PCI slots. AGP is dark brown in color usually. It's a 64 bit interface.

PCI-X

PCI -X is known as PCI Extended is an enhanced version but backward-compatible with existing PCI cards It improves upon the speed of PCI from 133 MBps to as much as 1 Gbps PCI-X was designed to increase performance of high bandwidth devices, such as Gigabit Ethernet and Fibre Channel and processors

PCI Express

PCI Express or PCIe, (formerly known as 3GIO for 3rd Generation I/O, not to be mistaken for PCI-X) is an implementation of the PCI computer bus that uses existing PCI programming concepts.

A connection between any two PCIe devices is known as a "link", and is built up from a collection of 1 or more lanes. All devices must minimally support single-lane (x1) links. Devices may optionally support wider links composed of 2, 4, 8, 12, 16, or 32 lanes. This allows for very good compatibility in two ways. A PCIe card will physically fit (and work correctly) in any slot that is at least as large as it is (e.g. an x1 card will work in an x4 or x16 slot), and a slot of a large physical size (e.g. x16) can be wired electrically with fewer lanes (e.g. x1 or x8; however it must still provide the power and ground connections required by the larger physical slot size). In both cases, the PCIe link will negotiate the highest mutually supported number of lanes. PCI Express is 64 bit interface.

PCI -X PCI -Express

Will have Two partition Known as PCI Extended

Will have One Partition in between

It doubles the data rate

Supports Gigabit Ethernet

Supports Fiber Channel

Data Transfer up to 8 Gbps

Mainly used for high transfer rates

Processor Socket and Slot

Sockets and slots on the motherboard are plenty and varied.

Sockets are basically flat and have several rows of holes arranged in a square. The processor slot is another method of connecting a processor to a motherboard, but one into which an Intel Pentium II or Pentium III.

Memory Slots

Memory or random access memory (RAM) slots are the next most prolific slots on a motherboard, and they contain the memory chips. There are varied types of memory available for PCs today. PCs today use memory chips arranged on a small circuit board.

These circuit boards are called Single Inline Memory Modules (SIMM) or Dual Inline Memory Modules (DIMM), depending on whether there are chips on one side of the circuit board or on both sides, respectively.

Aside from the difference in chip placement, memory modules also differ in the number of conductors, or pins, that the particular memory module uses. Some common examples include 30-pin, 72-pin, and 168-pin (the 168-pin modules are most often DIMM).

Additionally, laptop memory comes in smaller form factors known as Small Outline DIMM (SODIMM).

The Motherboard

On-Board Floppy and Hard Disk Connectors

Most drives need a connection to the motherboard so the computer can -talk‖ to the disk drive. These connections are known as drive interfaces and are of two types: floppy drive interfaces and hard disk interfaces. Floppy disk interfaces allow floppy disk drives to be connected to the motherboard and, similarly, hard disk interfaces do the same for hard disks. Most motherboards manufactured today include both the floppy disk and hard disk interfaces embedded on the motherboard.

On Board SATA connector

Serial Advanced Technology Attachment(SATA) is an interface for connecting hard drives to a computer. Unlike IDE which uses parallel signaling, SATA uses serial signaling technology. Because of this the SATA cables are thinner than the ribbon cables used by IDE hard drives. SATA cables can also be longer allowing you to connect to more distant devices without fear of signal interference. There is also more room to grow with data transfer speeds starting at 150 MB/s.

Keyboard Connectors

The most important input device for a PC is the keyboard. All PC motherboards contain a connector that allows a keyboard to be connected directly to the motherboard through the case. There are two main types of keyboard connectors: AT and PS/2. The AT connector is round, about 1/2 inch in diameter, and has five sockets in the DIN-5 configuration.

The PS/2 connector is smaller and more common than the AT connector. Most new PCs you can purchase today contain a PS/2 keyboard connector as well as a PS/2 mouse connector right above it on the motherboard.

The Motherboard Peripheral Ports and Connectors

In order for a computer to be useful and have the utmost functionality, there must be a way for the data to arrive and depart. Many different ports are available for this purpose.

Briefly, the seven most common types of ports you will see on a computer are serial, parallel, Universal Serial Bus (USB), Vi deo, Ethernet, Sound in/out, and Game ports.

Typical 9-pin and 25-pin serial ports

The above Figure shows an example of the two different types of serial ports: 9pin male and 25-pin male.

A Parallel Port

The above Figure shows a typical parallel port (also called a printer port, because the most common peripheral connected to it is a printer).

A Universal Serial Bus (USB) Port A Video Port

Universal Serial Bus (USB) ports look slightly different, as shown in the figure above. Video (SVGA) ports (as shown above) are found on motherboards that have builtin video circuitry to allow the computer to display images on a monitor. The video port is typically a 15-pin, three row, female connector.

An Ethernet Port

If your motherboard has an Ethernet network adapter integrated into its circuitry, you may see an Ethernet port (as shown above), an RJ-45 port, attached to the motherboard.

A Game Port

The above figure shows an example of a game port (also called a joystick port because that's the most common device connected to it). Game ports are used to connect peripheral devices to the computer and use a 15-pin female connector.

Connecting a port to the motherboard with the Dongle Method Peripheral ports Directly Soldered to a Motherboard

There are two ways of connecting these ports to the motherboard (assuming the circuitry for providing these functions is integrated into the motherboard). The first, called a dongle connection, allows you to mount the ports into the computer's case with a special cable (called a dongle). The dongle for each port connects to the respective pins on the motherboard for that port.

The second method of connecting a peripheral port is known as the direct-solder method. With this method, the individual ports are soldered directly to the motherboard. This method is used mostly in integrated motherboards in non-clone machines. Figure above shows peripheral ports connected to a motherboard with the direct solder method. Notice that there is no cable between the port and the motherboard and that the port is part of the motherboard.

Microprocessor

Microprocessor is the brain of any computer that does all the arithmetic computations & logical instructions inside the CPU. Microprocessor also communicates and controls activities between all peripherals including hard drive, RAM, multimedia devices and other components of a PC. Microprocessors comprise millions of transistors that contribute to performing additions, subtractions, multiplications, divisions and much more complex instructions.

Initial computing was about using small programs like basic spreadsheets, word processors, simple calculations and some progr amming. Today's computing requires more powerful hardware to compete with much powerful programs including complex calculations, graphic designing, gaming, multimedia and much demanding development software.

The Factors which affect the performance of a processor are as follows:

Clock Speed

The clock speed is the frequency with which a processor executes instructions. This frequency is measured in millions of cycles per second (megahertz [MHz]) or billions of cycles per second (gigahertz [GHz]). Generally speaking, the higher the MHz value, the faster the PC.

Cache Memory

Cache memory is a storage area for frequently used data and instructions. It requires a small amount of physical RAM that can keep up with the processor; it uses this RAM for storage. The processor contains an internal cache controller that integrates the cache with the CPU. The controller stores frequently accessed RAM locations to provide faster execution of data and instructions. This type of cache is known as a level 1(L1) cache.

Caching, in PC terms, is the holding of a recently or frequently used code or data in a special memory location for rapid retrieval. Speed is everything when it comes to computers. Mass storage is much slower than RAM, and RAM is much slower than the CPU. The high-speed memory chip generally used for caching is called static RAM (SRAM).

L1 Cache L2 Cache L3 Cache

In addition to external memory (RAM) will improve the performance as it is much faster than RAM, found integrated along with the processor.

In addition to L1 Cache & DRAM, it was available on the motherboard earlier and now "in-built" today in most of the processors.

In addition to L1 and L2 Cache, available in recent processor Intel Pentium IV HT Extreme edition, improves performance much better.

Microprocessor The Bus

The processor's ability to communicate with the rest of the system's components relies on the supporting circuitry. The system board's underlying circuitry is called the bus. The computer's bus moves information into and out of the processor and other devices, allowing all the devices to communicate with each other. The bus consists of several components, including the external bus, the data bus and the address bus.

The External Bus (System Bus)

The external bus is also referred to as the system bus or expansion bus. The expansion bus is a bus system that allows the processor to talk to another device. It is known as an external bus system because it is outside the processor. The devices are connected through expansion cards and slots. An expansion card is a removable circuit board that expands the capability of the computer.

The Data Bus

The data bus is used to send and receive data. The larger the bus width, the more data that can be transmitted (and, therefore, the faster the bus).

Data in a computer is transferred digitally. A single wire carries +3.3V or +5V to indicate a 1 data bit; it carries 0 volts to indicate a 0 data bit. (Remember, computers use the binary system to transmit information.) The greater number of wires allows more bits to be transmitted simultaneously.

For example, a 16-bit data bus width has 16 wires to transmit data, and a 32-bit data chip can transmit twice the amount of data as a 16-bit chip. A good comparison is the highway system. A single traffic lane allows only one car through at a time, whereas two lanes allow twice the amount of traffic to pass.

locations. These locations are used for data being sent or retrieved. The address bus carries a single bit of information, representing a digit in the address, along each wire. The size of the address bus corresponds to the number of address locations. The larger the address bus, the more memory address locations can be supported. The more memory address locations a processor can address, the more RAM a processor can use.

speed of the bus and the speed of the processor are directly related. Typically, the bus speed is set to 66MHz, 100MHz, or 133MHz plus a multiplier. For example, if you have a 450MHz processor, you set the processor speed jumper to 450MHz, the expansion bus speed to 100MHz, and the multiplier to 4.5 (4.5 × 100MHz = 450MHz). Speeds for processors below 200MHz are generally set without a multiplier.

Microprocessor Voltage

As discussed earlier, power supplies provides voltage(+5VDC and +3.3VDC) for the computer. However, processors often run at different voltages than the standard power supplies provide. Therefore, you need a small module known as a Voltage Regulator Module (VRM). The VRM regulates the voltage fed to the processor. For example, if a processor requires 1.5VDC, the VRM steps down the voltage so the processor has the correct voltage.

Interrupt Request(IRQ)

Interrupts are special lines connected directly to the processor. A device uses an interrupt to get the attention of the CPU when it needs to. It's rather like the cord you use to signal the driver when you need to get off at the next stop when you're a passenger on an actual bus. Just as you would use the -stop requested‖ cord to send a signal when you need the bus driver's attention,a computer device uses the interrupt request (IRQ) line to get the attention of the CPU.

IRQ Number Typical Use Description

IRQ 0

System timer This interrupt is reserved for the internal system timer. It is never available to peripherals or other devices.

IRQ 1 Keyboard

This interrupt is reserved for the keyboard controller. Even on devices without a keyboard, this interrupt is exclusively for keyboard input.

IRQ 2 Cascade interrupt for IRQs 8-15

This interrupt cascades the second interrupt controller to the first.

IRQ 3

Second serial port (COM2) The interrupt for the second serial port and often the default interrupt for the fourth serial port (COM4).

IRQ 4

First serial port (COM1) This interrupt is normally used for the first serial port. On devices that do not use a PS/2 mouse, this interrupt is almost always used by the serial mouse. This is also the default interrupt for the third serial port (COM3).

IRQ 5

Sound card This interrupt is the first choice that most sound cards make when looking for an IRQ setting.

DMA Channels

The bus also allows devices to bypass the processor and write their information directly into main memory. This feature is known as Direct Memory Access (DMA). Each type of bus has a different number of channels that can be used for DMA. If two devices are set to the same DMA channel, neither devic e will write information to memory correctly; thus, neither device will work.

DMA Channel # Use Notes

Microprocessor Form Factors

A processor form factor is the way the package of the processor is laid out, including how many pins it has, and the composition and size of the processor itself. Some of the most common Intel processor form factors include:

PGA Package Type

PGA stands for Pin Grid Array, which is the way the pins on the processor are laid out. These pins interface with the small wafer of silicon inside the processor package and are inserted into a motherboard socket. The PGA package has a nickel-plated copper heat sink on top to help with thermal conductivity. The pins on the bottom of the processor are laid out such that the processor can be inserted only one way (to prevent accidental damage by incorrect installation). The

SECC Package Type

The Single Edge Contact Cartridge (SECC) is a style of processor package in which the CPU is soldered directly to a small circuit board that has many gold finger contacts. These fingers on this circuit board make a connection with the contacts in a motherboard slot connector. The SECC is covered with a metal shell to protect the processor and to provide heat dissipation. This cartridge may also have an integrated L2 cache.

The SECC package was used in the Intel Pentium II processors (with 242 contacts) and the PGA package is primarily used by the Intel Xeon processor, which has 603 pins.

Pentium II Xeon and Pentium III Xeon processors (with 330 contacts).

SECC2 Package Type

The SECC2 package type is similar to the SECC package type, but the SECC2 plugs into the Slot 1 connector and does not use the metal heat sink. SECC2 was used with later model Pentium II and early model Pentium III processors.

PPGA Package Type

The Plastic Pin Grid Array (PPGA) package is similar to the PGA package type; however, the pins are staggered differently. The pins are arranged so that the processor can be inserted only one way into its socket. PPGA also has the nickel-plated copper heat sink on top. This package type was used primarily by early Intel Celeron processors with 370 pins that fit into a Socket 370.

FC-PGA2 Package Type

The FC-PGA2 package type is almost identical to the FC-PGA package type, with one important difference: The FC-PGA2 package includes what is known as an Integrated Heat Sink (IHS). This heat sink is attached directly to the processor during manufacturing. You can't mistake the FC-PGA2 for FC-PGA, because of the large copper or metal block on the top of the processor. Because it is directly attached to the die, it is a more efficient heat sink and can better conduct heat away from the processor.

This package is used primarily with the Intel Celeron and Pentium III with 370 pins and the Pentium 4 with 478 pins.

Inserting a microprocessor

1. Raise the locking lever align the chip, and gently insert it 2. One corner has a missing pin, an arrow, and a beveled edge, and there's a corresponding corner on the socket 3. Lock the chip in place with the locking lever Note: Socket is a Zero insertion force socket and doesn't need any force to insert a chip. The chip goes in only one way

775-land LGA Package

The Intel® Pentium®4 processor on 90 nm process in the 775-land package is a follow on to the Pentium 4 processor in the 478-pin package with enhancements to the Intel Net Burst® micro architecture. The Pentium 4 processor on 90 nm process in the 775-land package uses Flip-Chip Land Grid Array (FC-LGA4) package technology, and plugs into the 775LGA socket. The Pentium 4 processor in the 775-land package, like its predecessor, the Pentium 4 processor in the 478-pin package, is based on the same Intel 32-bit micro architecture and maintains the tradition of compatibility with IA-32 software.

How Microprocessors work?

Microprocessors are made of millions of transistors and it performs three simple steps:

Fetch: Get the instruction from the memory

Decode:

Find out what has to be done

Execute: Process the instruction

Millions of instructions will be processed within a second based on the speed of the processor. Intel's first microprocessor 4004 that had mere 2300 transistors can just perform 60,000 calculations per second. Today's processor like Pentium IV running at blazing speeds can do over million times faster. For the sequence to happen, the processor internally is made of various execution units as discussed in the following section "Inside the MP".

The computer industry is very profitable, so many companies make CPUs for PCs. The market leader in the manufacture of chips is Intel Corporation. Intel's competition includes Motorola, Advanced Micro Devices (AMD), Cyrix, and IBM. When it first began making CPUs for the IBM PC, Intel shared its designs with other manufacturers; but with the introduction of the 80386 model in 1985, Intel ceased licensing its designs.

Intel Processors

When the first PC was introduced, IBM decided to go to the chip manufacturer Intel for a CPU. Since then, Intel has been the CPU supplier for almost all IBM-compatible computers.

Chip

Year

Memory

Memory is the electronic holding place for instructions and data that your computer's microprocessor can reach quickly.When your computer is in normal operation ,its memory usually contains the main parts of the operating system and some or all of the application programs and related data that are being used. Memory is often used as a shorter synonym for Random Access Memory(RAM).

All computer memory is used to hold binary strings of data to be manipulated by the CPU. Think of memory as a vast bank of switches with two positions: on or off. Off is given the value of 0; on is given the value of 1. This allows the switches to hold binary data based on whether they are open or closed. By stringing a series of switches together, larger numbers and code values can be represented.

Memory is one of the most popular, easy, and inexpensive ways to upgrade a computer. As the computer's CPU works, it stores information in the computer's memory.

ROM PROM EPROM EEPROM

There are two major classes of computer memory:

Non -Volatile

The Memory is said to be Non Volatile, if the data is retained even though the power to the computer is shut off. The setup data held in CMOS (complementary metal-oxide semiconductor), is a good example of nonvolatile memory.

Volatile

The memory is said to be Volatile, if the data is lost when the computer loses the power. The RAM is an volatile memory

The various types of Non-Volatile Memory are as follows:

ROM

ROM stands for Read-Only Memory. It is called read-only because it cannot be written to. Once information has been written to the ROM, it cannot be changed. ROM is normally used to store the computer's BIOS, because this information normally does not change.

Types of ROM

Mask-Programmed ROM (MROM) -programmed at the factory. Programmable ROM (PROM) -can be custom-programmed by the user (once) using special circuitry.

Erasable-Programmable ROM (EPROM) -can also be programmed and erased by the user using ultraviolet light and special circuitry external to the computer.

Electrically Erasable PROM (EEPROM) -can be erased and reprogrammed by special circuitry within the computer.

CMOS

CMOS is a special kind of memory that holds the BIOS configuration settings. CMOS memory is powered by a small battery so the settings are retained when the computer is shut off. The BIOS reads information such as the hard drive types which are configured for this computer to use, the drive(s) it should search for boot sectors, and so on. CMOS memory is usually not upgradable in terms of its capacity.

The various types of Volatile Memory are as follows:

RAM RAM (Random Access Memory) is most often referred to when PC memory is discussed. RAM is the form of volatile memory used to hold temporary instructions and data for manipulation while the system is running. The term random is applied because the CPU can access or place data to and from any addressable RAM on the system. If power to the system is lost, all RAM is lost as well.

SRAM DRAM

Dynamic Random Access Memory (DRAM) was an improvement over SRAM. DRAM uses a different approach to storing the 1s and 0s. Instead of transistors, DRAM stores information as charges in very small capacitors. If a charge exists in a capacitor, it's interpreted as a 1. The absence of a charge will be interpreted as a 0. Because DRAM uses capacitors instead of switches, it needs to use a constant refresh signal to keep the The S in SRAM stands for static. Static random access memory does not require a refresh signal like DRAM. The chips are more complex and are thus more expensive. However, they are faster. DRAM access times come in at 80 nanoseconds (ns) or more; SRAM has access times of 15 to 20 ns. SRAM is often used for cache memory.

information in memory. DRAM requires more power than SRAM for refresh signals and, therefore, is mostly found in desktop computers. DRAM technology allows several memory units, called cells, to be packed with very high density. Therefore, these chips can hold very large amounts of information. Most PCs today use DRAM of one type or another.

FAST PAGE MODE (FPM)

At one time, FPM was the most common form of DRAM found in computers. In fact, it was so common that people simply called it "DRAM," leaving off the "FPM". FPM offered an advantage over earlier memory technologies because it enabled faster access to data located within the same row.

EXTENDED DATAOUT (EDO)

In 1995, EDO became the next memory innovation. It was similar to FPM, but with a slight modification that allowed consecutive memory accesses to occur much faster. This meant the memory controller could save time by cutting out a few steps in the addressing process. EDO enabled the CPU to access memory 10 to 15% faster than with FPM.

Synchronous DRAM (SDRAM) Double Data Rate SDRAM (DDR SDRAM)

SDRAM was developed to match the ever-increasing processing speeds of the Pentium systems. SDRAM, as its name suggests, is synchronized to the speed of the systems in which it will be used (PC66 SDRAM runs at 66MHz, PC100 runs at 100MHZ, PC133 runs at 133MHz, and so on). Synchronizing the speed of the systems prevents the address bus from having to wait for the memory because of different clock speeds.

Essentially, Double Data Rate SDRAM (DDR SDRAM) is clock-doubled SDRAM. The memory chip can perform reads and writes on both sides of any clock cycle (the up or start and the down or ending), thus doubling the effective memory executions per second. So, if you are using DDR SDRAM with a 100MHz memory bus, the memory will execute reads and writes at 200MHz and transfer the data to the processor at 100MHz. The advantage of DDR over regular SDRAM is increased throughput, and thus increased overall system speed.

RDRAM

With densities up to 256Mbit, RDRAM components are available in volume from leading memory suppliers in a range of speeds from 800MHz to 1200MHz. For systems requiring upgrade flexibility, RDRAM devices may be configured into single-, dual-or quad-channel RIMM modules to support bandwidths from 1.6 GB/sec to 10.7 GB/sec and system memory capacities up to 8GB. Both RDRAM memory devices and RIMM modules are tested for specification compliance with an extensive validation program that also promotes system inter-operability. Additionally, standard RDRAM memory controllers are available in a wide range of ASIC and foundry processes in a variety

Caching: The Layered Look

Caches are organized into layers. The highest layer is closest to the device (such as the CPU) using it. On early PCs, caches were usually separate chips. Today, it is not uncommon to have two levels of cache built right into the CPU.But a cache is not limited to dynamic memory. Mass storage devices like hard drives can also be used to store less commonly used code or data.

Internal Cache (L1)

Starting with the 486 chips, a cache has been included on every CPU. This original on-board cache is known as the L1 (level 1) or internal cache. All commands for the processor go through the cache. The cache stores a backlog of commands so that if a wait state is encountered, the CPU can continue to process using commands from the cache. Caching will store any code that has been read and keep it available for the CPU to use. This eliminates the need to wait for fetching of the data from DRAM.

External Cache (L2)

Additional cache can be added to most computers, depending on the motherboard. This cache is mounted directly on the motherboard, outside the CPU. The external cache is also called L2 (level 2) and is the same as L1, but larger. L2 can also (on some motherboards) be added or expanded. When installing any L2 cache, be sure to check the CMOS setup and enable the cache. Some computer systems are now also employing a Level 3 cache.

Notes

Computer Memory can also be classified as follows:-

Input Devices

Let's start this chapter off by talking about some of the most commonly used peripheral devices: input devices. As their name suggests, input devices exist so that human beings can communicate with the object we call a computer. These devices interpret the intentions of their users (via a keystroke or some other movement) to tell the computer to perform some action. Without them, the computer would be of little use to us.

Mouse A mouse is an input device which allows the user to control a cursor to manipulate data without complicated commands. The mouse or mice was invented by Douglas Englebart in 1963, who at the time was working at the Stanford Research Institute. Today the mouse are now found on every Apple and PC computer and used with various different GUIs.

Touch screens

A touch screen is an intuitive computer input device that works by simply touching the display screen, either by a finger, or with a stylus, rather than typing on a keyboard or pointing with a mouse. Computers with touch screens have a smaller footprint, and can be mounted in smaller spaces; they have fewer movable parts, and can be sealed. Touch screens may be built in, or added on. Add-on touch screens are external frames with a clear see-through touch screen which mount onto the monitor bezel and have a controller built into their frame. Built-in touch screens are internal, heavy-duty touch screens mounted directly onto the CRT tube. Any touch screen system comprises the following three basic components;

Touch screen sensor panel -it sits above the display and generates appropriate voltages according to touch. Touch screen controller -it processes the signals received from the sensor and translates these into touch event data which is passed to the PC's processor, usually via a serial or USB interface A software driver-it provides an interface to the PC's operating system and translates the touch event data into mouse events, essentially enabling the sensor panel to "emulate" a mouse.

Keyboard

The most common PC input device is the keyboard. This type of device translates keystrokes into letters or numbers. The letters are then interpreted and commands are performed, depending on what is being sent.

Types of Keyboards

Keyboards have changed very little in layout since their introduction. In fact, the most common change has simply been the natural evolution of adding more keys that provide additional functionality.

The most common keyboards are:

101-key Enhanced keyboard 104-key Windows keyboard 82-key Apple standard keyboard 108-key Apple Extended keyboard Portable computers such as laptops quite often have custom keyboards that have slightly different key arrangements than a standard keyboard. Also, many system manufacturers add specialty buttons to the standard layout. A typical keyboard has four basic types of keys:

Typing Keys Numeric keypad Function keys Control keys

Types of Mouse and its Technologies

Mechanical Mice

Mechanical Mice requires that the mouse be set on a flat surface. The distance and the speed of the rollers inside the mouse determines how far the mouse cursor moves on the screen depending on the software configuration.

Optical Mice

Optical Mice require a special mouse pad which has a grid pattern. A sensor inside the mouse determines the movement by reading the grid as the mouse passes over it while emitting a light from an LED or sometimes a laser. This type of mouse is much more accurate than the ordinary optical mechanical mouse which relies on the traction between the mouse ball and the rollers. One drawback to an optical mouse is they can have problems in bright lights.

New Optical Mice no longer have the disadvantages of earlier mice and are capable of being utilized on any surface. In comparison to the traditional Optical-Mechanical mouse the Optical is a much better solution for a computer mouse.

Optical-Mechanical

The optical-mechanical hybrid consists of a ball which rolls a wheel inside the mouse. This wheel contains a circle of holes and or notches to read the LED by a sensor as it spins around when the mouse is moved. This mouse is much more accurate than the mechanical mouse. This mouse is now the most commonly used mouse with PC and Macintosh computers. See how a mouse works for an illustration and a more in-depth explanation of how this mouse works.

Interfaces

These are the following ways in which the mouse can be connected to a computer:

Blue tooth Infrared PS/2 Port Serial Port USB

How a Mouse Works

As you can see in the illustration the mouse movement is tracked by four parts. As the mouse is moved, the ball rolls in the direction of the movement which in turn moves the roller (X or Y axis). As the roller begins to rotate so does the chopper / gear. The gear has small notches within it or around the edges of it, as it rotates light shines through the openings which is then detected by the two light sensors which then sends the computer a signal of that movement. The offset of the light received by the two light sensors determines the direction of each axis.

Within the mouse you will find a total of two rollers and choppers / gears. Each roller represents a X or Y axis which is the Horizontal or Vertical movement of the mouse cursor.

Scanner

In addition to using keyboards and pointing devices, there is another very common method of getting data into a computer. The charge-coupled device (CCD) was developed to allow light (and shades of light) to be converted into electrical pulses. This opened up the arena to allow a new breed of devices to input data to a computer.

The largest class of these devices are scanners. Optical scanners (their full name) use CCDs and a light source to convert pictures into a stream of data.

Optical Storage Device

CD-ROM Drives

A CD-ROM (CD-ROM stands for Compact Disc-Read-Only Memory) is an optical storage device which is accommodated by a CD-ROM drive.These drives are slightly different from other storage media in several ways. First, they read information differently than magnetic media disk drives do. CD-ROM drives use laser light to read the information from the media, they are described as optical drives.

Another difference between magnetic media and CD-ROM drives is that CD-ROM drives are read-only devices ( Compact Disc-Read-Only Memory). The only way to write to a CD-ROM is during manufacture time, when the pits are burned into the substrate of the disc. Once written, they cannot be erased.Today, using the latest writable and re-writable CDs we can write new data as well as erase existing and re-write new data.

When reading information from a CD, the drive basically reads a lot of pits and lands (lands are the spaces between the pits) in the disc surface. The pits are etched into the CD at production time. The laser reflects off the CD's surface and onto a sensor. The sensor detects the pattern of pits and lands as the disc rotates and translates them into patterns of 1s and 0s. This binary information is fed to the computer that is retrieving the data.

A CD-ROM disc has a single track that runs from the center to the outside edge, exactly the reverse of the groove on a record. A CD-ROM uses basically the same technology as the audio compact discs used in most homes today. When a CD-ROM is placed into a CD-ROM drive, a motor spins the CD at a specific rate. A laser that reads the CD is then activated.Due to these basic similarities, several compatibilities exist between the different compact disc technologies. For example, it is possible to play audio CDs in a computer's CD-ROM drive. Also, some computer CDs have audio tracks on them and are made to be used in either type of CD drive (home audio or computer).

Tracks & Sectors

A hard disk is really a set of stacked "disks," each of which has data recorded electromagnetically in tracks on the disk. A "head" records (writes) or reads the information on the tracks. Two heads, one on each side of a disk, read or write the data as the disk spins. A sector contains a fixed number of bytes -for example, 256 or 512. Either at the drive or the operating system level, sectors are often grouped together into clusters. The process of low-level formatting a drive, establishes the tracks and sectors on the platter. High-level formatting then writes the file-storage structures, like the fileallocation table, into the sectors. This process prepares the drive to hold files.

Storage Devices Floppy Disk Drives

The floppy disk drive is the most commonly used magnetic storage device. Floppy disks have only one platter encased in a plastic shell and are available in different capacities.

A floppy drive has either one or two read/write heads. Each head moves in a straight line on a track over the disk rather than on an angular path as with fixed disk systems. When the disk is placed into the drive, a motor engages the center of the disk and rotates it in 3600RPMs speed. This action moves the tracks past the read/write heads.

1/4-Inch Floppy Disk 3 1/2-Inch Diskette

The 5 1/4-inch floppy disks are made from a polyester disk coated with iron oxide and a flexible outer covering. The disk has a large hole in the center, called the drive hole, which the motor in the disk drive uses to spin the disk. In addition, a 11/2-inch oval window is cut into the case to allow the read/write heads access to the disk media. A small round hole cut into the disk shell next to the drive hole lines up with an even smaller hole cut into the disk media. When this smaller hole spins past the slightly larger hole in the shell, it allows a light to shine all the way through the disk system. In this way, the floppy drive can tell how fast the disk is rotating by how many times per second that hole appears.

Finally, a notch is cut in one side of the disk. This notch is called the write protect tab. When a disk is inserted into a floppy drive, a small lever places itself into this notch. When the lever is in the notch, the disk can be written to. You can writeprotect the disk (which prevents it from being written to) by covering this hole.

Tape Drives

The final type of magnetic media drive is tape drive.The tape cartridge uses a long polyester ribbon coated with magnetic oxi de wrapped around two spools. As the tape unwinds from one spool, it passes by a read/write head in the drive that retrieves or saves the information. It then proceeds to the other spool where it is kept until needed again.

Tape media is great for large-capacity storage, but it is relatively slow because it uses sequential read-write operation.The best application for tape media is making backups. Current tape technology uses 4mm or 8mm Digital Audio Tape (DAT) or Digital Linear Tape (DLT) for its storage medium. With these technologies, it is possible to store up to 70GB of data on a sin

Storage Devices

What good is a computer without a place to put everything? Storage media hold the data being accessed, as well as the files the system needs to operate, and data that needs to be saved. When everything is done and information needs to be stored, where should it be kept? The many different types of storage differ in terms of their capacity (how much they can store), access time (how fast the computer can access the information), and the physical type of media being used.

Storage devices hold data, even when the computer is powered off. The physical material that actually holds data is called storage medium. The hardware that writes or reads data from a storage medium is called as a storage device. Storage devices would include magnetic, optical and Chips

Magnetic Storage Device

Disk Drives

A disk drive is an encasement which accommodates a disk and helps to read and write data on the disk .There are different types of disk drives for different types of disks :-Hard disk drive ( HDD )-Floppy disk drive ( FDD )

Hard Disk Drives

Hard disks actually contain several disks called platters, stacked together and mounted through their centers on a small rod called a spindle. The disks are rotated about this rod at a speed between 2,000 and 10,000 revolutions per minute (RPM). As the disks rotate, one or more read/write heads float approximately 10 micro inches (about one-tenth the width of a human hair) above the disk surfaces and make, modify, or sense changes in the magnetic positions of the coatings on the disks. Several heads are moved together as one unit by an actuator arm. There is usually one head for each side of a platter.

This entire mechanism is enclosed in a hard disk case. These disks are also called fixed disks because the mechanism is not designed to be removed. The disk platters, though perfectly free to revolve at high RPM, are otherwise fixed in place.

SATA

Ports and Connectors

A port is a place where data arrives or departs in a computer .There are two types of ports:

-Physical ports -Eg. Serial, parallel, game and USB.

-Logical ports -Eg. HTTP, FTP, TCP, Telnet, SMTP etc.

Peripheral Port Connector Types

DB-Series

DB connectors, the most common style of connector found on computers today, are typically designated with DB-n, where the letter n is replaced by the number of connectors. DB connectors are usually shaped like a trapezoid.

The nice part about these connectors is that only one orientation is possible. If you try to connect them upside down or try to connect a male connector to another male connector, they just won't go together, and the connection can't be made.

RJ-Series

Registered Jack (RJ) connectors are most often used in telecommunications. Figure shows the two most common examples of RJ ports and connectors: RJ-11 and RJ-45. RJ-11 connectors are used most often in telephone hookups; your home phone jack is probably an RJ-11 jack or port. RJ-45 connectors, on the other hand, are most commonly found on Ethernet networks that use twisted pair cabling.

On the left in this picture is an RJ-11 connector and on the right is an RJ-45 connector. Notice the size difference.

As you can see, RJ connectors are typically square with multiple gold contacts on the top (flat) side. A small locking tab on the bottom prevents the connector and cable from falling or being pulled out of the jack accidentally.

Ports and Cables Universal Serial Bus (USB) RCA

Most computers built after 1997 have one or two flat ports in place of one DB-9 serial port. These ports are Universal Serial Bus (USB) ports, and they are used for connecting multiple (upto 127) peripherals to one computer through a single port (and use of multi port peripheral hubs). USB version 1.1 supported data rates as high as 12Mbps (1.5MBps). The newest version, USB 2.0, supports data rates as high as 480Mbps (60MBps).

Because of USB's higher transfer rate, flexibility, and ease of use, most devices that in the past used serial interfaces now come with USB interfaces.

The RCA port was developed by the RCA Victor company in the late 1940sfor use with its phonographs. RCA jacks and connectors are used to transmit both audio and video information. You will find RCA connectors on the sound card which are used for Mic In, Line In and Line out.

Infrared

Increasing numbers of people are getting fed up with being tethered to their computers by cords. As a result, many computers (especially portable computing devices like laptops and PDAs) are now using infrared ports to send and receive data. An infrared port is a small port on the computer that allows data to be sent and received using electromagnetic radiation in the infrared band. The infrared port itself is a small, dark square of plastic (usually a very dark maroon) and can typically be found on the front of a PC or on the side of a laptop or portable.

Infrared transmissions are simply wireless transmissions that use radiation in the infrared range of the electromagnetic spectrum. Many laser printers (and some computers) come with infrared transmitter/receivers (transceivers) so that they can communicate with the infrared ports on many handhelds. This allows the user of a PDA, handheld, or laptop to print to that printer by pointing the device at the printer and initiating the print process.

As far as configuring the interface is concerned, very little needs to be done. The infrared interfaces are enabled by default on most computers, handhelds, and printers equipped with them. The only additional item that must be configured is the print driver on the PDA, handheld, or computer. The driver must be the correct one for the printer to which you are printing.

Centronics

The last type of port connector is the Centronics connector. It has a unique shape. It consists of a central connection bar surrounding by an outer shielding ring. The Centronics connector is primarily used in parallel printer connections and SCSI interfaces. It is most often found on peripherals, not on computers themselves (except in the case of some older SCSI interface cards).

Infrared ports send and receive data at a very slow rate (maximum speed on PC infrared ports is less than 4Mbps).

PS/2 (Keyboard and Mouse)

A PS/2 port (also known as a mini-DIN 6 connector) is a mouse and keyboard interface port first found on the IBM PS/2. It is smaller than previous interfaces (the DIN-5 keyboard port and serial mouse connector), and thus its popularity increased quickly. You can tell the difference because usually the keyboard port is purple and the mouse port is green. Also, typically there are small graphics of a keyboard and mouse, respectively, imprinted next to the ports.

VGA port

The last type of port connector is the Centronics connector. It has a unique shape. It consists of a central connection bar surrounding by an outer shielding ring. The Centronics connector is primarily used in parallel printer connections and SCSI interfaces. It is most often found on peripherals, not on computers themselves (except in the case of some older SCSI interface cards).

pin serial port 9 pin Serial port

RJ-45-port

Game port USB port Parallel port

Ports and Cables Common Peripheral Cables

An interface is a method of connecting two dissimilar items together. A peripheral interface is a method of connecting a peripheral or accessory to a computer, including the specification of cabling, connector type, speed, and method of communication used.

The most common interfaces used in PCs today include:

For each type, let's look at the cabling and connector used as well as the type(s) of peripherals that are connected.

Parallel

Most parallel cables use a DB-25 male connector on one end and either a DB-25 male connector or Centronics-36 connector on the other. Printer cables typically used the DB-25M to Centronics-36 configuration.Inside a parallel cable, eight wires are used for transmitting data, so one byte can be transmitted at a time.

Serial

Almost every computer made since the original IBM PC has at least one serial port.

They are easily identified because they have either a DB-9 male or DB-25 male port.

Standard serial ports have a maximum data transmission speed of 57Kbps and a maximum cable length of 50 feet.Serial cables come in two common wiring configurations, standard serial cable and null modem serial cable. A standard serial cable is used to hook various peripherals like modems and printers to a computer.

Ports and Cables Universal Serial Bus (USB) IEEE 1394 (Fire Wire)

The USB interface is very straightforward. Essentially, it was designed to be plug and play -just plug in the peripheral, and it should work (provided the software is installed to support it). The USB cable is simple: a USB male connector on each end.

Sometimes manufacturers put a mini connector on one end to make it fit the form factor of the device that needs a USB connection.

One part of the USB interface specification that makes it so appealing is the fact that if your computer runs out of USB ports, you can simply plug a device known as a USB hub in to one of your computer's USB ports, which will give you several more USB ports from one USB port. USB cables are used to connect a wide variety of peripherals to computer, including mice, digital cameras, printers, and scanners.

USB's simplicity of use and ease of expansion make it an excellent interface for just about any kind of peripheral.

The IEEE 1394 interface is about one thing: speed. Its first iteration, now known as Fire -Wire 400, has a maximum data throughput of 400Mbps. The latest iteration, Fire Wire 800, has a maximum data throughput of 800Mbps. It caries data at that speed over a maximum cable length of 4.5 meters (Fire Wire 400) and 100 meters (Fire Wire 800 over fiber optic cables has maximum data throughout of 800Mbps).

Fire Wire uses a very special type of cable. It is difficult to mistake this cable for anything but a Fire Wire cable. Although most people think of Fire Wire as a tool for connecting their digital camcorders to their computers, it's much more than that. Because of its high data transfer rate, it is being used more and more as a universal, high-speed data interface for things like hard drives, CD-ROM drives, and digital video editing equipment.

RCA PS/2 (Keyboard and Mouse)

The RCA cable is simple. There are two connectors, usually male, one on each end of the cable. The male connector connects to the female connector on the equipment. An RCA male to RCA female connector is also available; it's used to extend the reach of audio or video signals.

The RCA male connectors on a connection cable are sometimes plated in gold to increase their corrosion resistance and to improve longevity.

The final interface we'll discuss is the PS/2 interface for mice and keyboards. Essentially, it is the same connector for the cables from both items: a male mini-Din 6 connector. Most keyboards today still use the PS/2 interface, whereas most mice are gravitating toward the USB interface (especially optical mice).

PS/2 ( Keyboard and mouse ) USB

There are two types of connectors on USB cables: a long, flat rectangle for plugging into computers and hubs called 'USB-A', and a smaller, square connector for plugging into devices like external CD and Hard drives, scanners, and printers called 'USB-B

BIOS ( Also known as ROM BIOS and Firmware ) and CMOS

BIOS stands for Basic Input/Output System. The BIOS communicates between the computer and devices. The BIOS is usually stored in ROM. It was created by IBM to act as a translator to run the same operating systems on different hardware platforms. When the operating system needs to access a piece of hardware, it would now ask the BIOS, rather than just taking control of the hardware. The use of BIOS prevented programs from fighting over hardware. As lon g as the operating system (such as DOS) uses the BIOS for its hardware requests, it can run on different hardware platforms. The BIOS creates a standard reference point for many different types of hardware.

BIOS Chip

Aside from the processor, the most important chip on the motherboard is the basic input/output system (BIOS) chip. This speci al memory chip contains the BIOS software that tells the processor how to interact with the rest of the hardware in the computer. The BIOS chip is easily identified: If you have a non-clone computer (Compaq, IBM, HP, and so on), this chip has on it the name of the manufacturer and usually the word BIOS. For example, the BIOS chip for a Compaq has something like Compaq BIOS printed on it.

For clones, the chip usually has a sticker or printing on it .

Flashing : Process of upgrading BIOS.

CMOS (Complementary Metal

Oxide Semiconductor) contains settings that determine how the computer is configured. These settings are user-configurable and can be accessed through the CMOS setup program by pressing some key combination at startup (such as Shift+F1 or Ctrl+Shift+Esc). For example, one setting in CMOS controls the boot sequence. The parameter is usually called boot sequence and can be set to either -A: C:‖ or -C: A:‖ (in most cases). Every CMOS setup program is different and uses different commands for configuration. Usually, though, the CMOS setup program is menu driven and will present you with a list of settings that you can configure, as well as the possible settings for them. When you're done configuring, you can press Esc and the CMOS setup program will ask you to press Enter to save the changes and reboot. After rebooting, the computer will operate with the modified settings.

Your PC has to keep certain settings when it's turned off and its power cord is unplugged. Some of these settings include: Date Time Hard drive configuration Memory

Your PC keeps these settings in a special memory chip called the Complimentary Metal-Oxide Semiconductor (CMOS RAM ) chip.

CMOS Battery

To maintain CMOS RAM settings, it is essential to have power constantly. When you shut down the computer and it stops receiving power supply , CMOS battery continues to provide power supply to CMOS RAM to main its contents.

BIOS and CMOS

Power-On Self Test

Every time a PC is powered on or reset using the Reset button or Windows Restart command, the computer is rebooted and reset to its basic operating condition. The POST determines whether the computer will display errors by beeping or showing them on the screen. The POST does not assume the video works until it has been tested. The POST does assume that the speaker always works, but to let you know that the speaker is working, all computers beep on st artup. Depending on the BIOS type, the POST might also sound a single beep when it's done to let you know the boot process was successful. If something goes wrong, the POST sends a series of beep codes to let you know what the problem is or where to start looking for it.

Beep Codes Before and During the Video Test

The purpose of the first POST test is to check the most basic components. The exact order, number of tests, and error states will vary from product to product. In a healthy system, the POST reports by using a series of beep codes and screen messages to convey that all components are working. Then it transfers control to the boot drive, which loads the operating system. The POST is a good indication that the hardware is in working status.

If a problem occurs, the POST routine attempts to report the problem. This is also done using beep codes and (if possible) screen prompts. Some error codes are specific to chip sets or custom products, and the exact message and meaning can vary from system to system. The following table lists the basic beep codes for AMI and Phoenix BIOS's.

Number of Beeps

Adapter Cards

An adapter card (also known as an expansion card) is simply a circuit board you install into a computer to increase the capabilities of that computer. Adapter cards come in many different kinds, but the important thing to note is that no matter what function a card has, the card being installed must match the bus type of the motherboard you are installing it into (for example, you can only install a PCI network card into a PCI expansion slot).

Four of the most common expansion cards that are installed today are as follows:

Video card Network interface card (NIC) Modem Sound card PCMCIA Expansion slots in laptop computers

Let's take a quick look at each of these cards, their functions, and what they look like.

Video Card

A video adapter (more commonly called a video card) is the expansion card you put into a computer in order to allow the computer to display information on some kind of monitor or LCD display. A video card also is responsible for converting the data sent to it by the CPU into the pixels, addresses, and other items required for display. Sometimes, video cards can include dedicated chips to perform certain of these functions, thus accelerating the speed of display. With today's motherboards, most video cards are AGP expansion cards that fit in the AGP slot on a motherboard.

Network Interface Card (NIC)

A network interface card (NIC) is an expansion card that connects a computer to a network so that it can communicate with other computers on that network. It translates the data from the parallel data stream used inside the computer into the serial data stream of packets used on the network. NIC card has one RJ45 connector. In addition to the NIC, you need to install software or drivers on the computer in order for the computer to use the network.

Modem Modulator DeModulator(Internal Modem)

Any computer that connects to the Internet via a dial-up connection needs a modem. A modem is a device that converts digital signals from a computer into analog signals that can be transmitted over phone lines and back again. These expansion card devices have one connector for the expansion bus being used (PCI or ISA) and another for connection to the telephone line. Actually, there are two RJ-11 ports: one for

Sound Card

Just as there are devices to convert computer signals into printouts and video information, there are devices to convert those signals into sound. These devices are known as sound cards. Many different manufacturers make sound cards, but the standard has been set by Creative Labs with its SoundBlaster series of cards.

A sound card typically has small, round, 1/8-inch jacks on the back of it for connecting to connection to the telephone line and the other for connection to a telephone. This is the case primarily so that putting a computer online still lets someone hook a phone to that wall jack (although they won't be able to use the phone while the computer is connected to the Internet).

PCMCIA

Originally stood for ‗Peripheral Component Microchannel Interconnect Architecture'

It was then renamed ‗Personal Computer Memory Card International Association', referring to the standards organization Version 2.0 specifications lead to the simpler name -‗PC Cards' microphones, headphones, and speakers as well as other sound equipment. Many sound cards also have a DB-15 game port which can be used for either joysticks or Musical Instrument Digital Interface (MIDI) connections (allows a computer to talk to a digital musical instrument, like a digital keyboard or similar).

Expansion slots in laptop computers

Types of NIC

There are different types of NICs available for different purposes. The major types are Wired NICs and wireless NICs. To connect a computer to a wired network a wired NIC is used. To connect a computer to a wireless network, wireless NIC is used. The main difference between a wired NIC and a wireless NIC is -Wired NIC has an RJ 45 port, whereas a wireless NIC has small transreceiving circuit to send and receive signals. There are other types of NICs as w ell. A 32-bit path is used for data transfer.

NIC Type

The operating speed is several times greater. CardBus works at lower battery voltage.

These CardBus cards can only be used with CardBus slots -they are keyed to prevent insertion into 16-bit slots so that the card and the slot won't be damaged by differing voltage requirements. 16-bit cards work in either type of slot, but CardBus cards only work in CardBus slots. A CardBus card will have a gold grounding shield strip across it, typically with 8 small metal bumps. This strip is necessary to prevent signal noise from interfering with CardBus high speed bus.

Cardbus PCMCIA

Display Devices

A way of getting information out of a computer is to use a computer display. Display systems convert computer signals into text and pictures and display them on a TV-like screen. As a matter of fact, the first personal computers used television screens because it was simple to use an existing display technology rather than to develop a new one. Several types of computer displays are in use today, including the TV. All of them use either the same cathode ray tube (CRT) technology found in television sets (almost every desktop monitor uses this technology) or the liquid crystal display (LCD) technology found on all laptop, notebook and palmtop computers.

Video Technologies

Let's first talk about the different types of video technologies. There are four major types: monochrome, EGA/CGA, VGA, and Super VGA. Each type of video technology differs in two major areas: the highest resolution it supports and the maximum number of colors in its palette. Resolution depends on how many picture units (called pixels) are used to draw the screen. The more pixels, the sharper the image. The resolution is described in terms of the screen's dimensions, indicating how many pixels across and down are used to draw the screen. For example, a resolution of 1,024 × 768 means 1,024 pixels across and 768 pixels down were used to draw the pixel grid. The video technology in this example would use 786,432 (1,024 × 768 = 786,432) pixels to draw the screen.

Monochrome

The first video technology for PCs was monochrome (from the Latin mono, meaning one, and chroma, meaning color). This black-and-white video (actually, it was green and white or amber and black) was fine for the main operating system of the day, DOS. DOS didn't have any need for color. Thus, the video adapter was very basic. The first adapter, developed by IBM, was known as the Monochrome Display Adapter (MDA). It could display text but not graphics and used a resolution of 720 × 350 pixels.

EGA and CGA

The next logical step for displays was to add a splash of color. IBM was the first with color, with the introduction of the Color Graphics Adapter (CGA). CGA could display text, but it displayed graphics with a resolution of only 320 × 200 pixels with four colors. It displayed a better resolution (640 × 200) with two colors-black and one other color. After a time, people wanted more colors and higher resolution, so IBM responded with the Enhanced Graphics Adapter (EGA). EGA could display 16 colors out of a palette of 64 with a resolution of 320 × 200 or 640 × 350 pixels.

Types of Monitors

Is bigger and bulkier when compared to the more modern flat screens Consumes more power when compared to flat screens A beam of electrons lights up pixels on the screen.

Consumes less power and occupies less space, owing to its flat nature Reflective twisted pneumatic liquid crystal display

Commonly used in notebooks, mobile phones, calculators etc.

Is also flat, but consumes more power than LCD displays A grid of conductors are sealed between two flat plates of glass; neon and/or argon gas fills the space between the plates Commonly used for TV displays Has a larger maximum practical size & better viewing angle than LCDs

VGA

The Video Graphics Array (VGA). This video technology had a whopping 256KB of video memory on board and could display 16 colors at 640 × 480 pixels or 256 colors at 320 × 200 pixels. It became widely used and has since become the standard for color PC video; it's the starting point for today's computers.

Super VGA

Video Electronics Standards Association (VESA) enhanced IBM's video technology and make the enhanced technology a public standard. The result of this work was Super VGA (SVGA). This new standard was indeed an enhancement, because it could support 256 colors at a resolution of 800 × 600 (the VESA standard), or 1,024 × 768 pixels with 16 colors, or 640 × 480 with 65,536 colors.

XGA

IBM introduced a new technology in 1991 known as the Extended Graphics Array (XGA). XGA could support 256 colors at 1,024 × 768 pixels or 65,536 colors at 640 × 480 pixels. It was a different design, optimized for GUIs like Windows or OS/2. It was also an interlaced technology, meaning that rather than scan every line one at a time to create the image, it scanned every other line on each pass, using the phenomenon known as persistence of vision to produce what appears to our eyes as a continuous image.

Monitors

As we have already mentioned, a monitor contains a CRT. But how does it work? Basically, a device called an electron gun shoots electrons toward the back side of the monitor screen. The back of the screen is coated with special chemicals (called phosphors) that glow when electrons strike them. This beam of electrons scans across the monitor from left to right and top to bottom to create the image.

Dot pitch

The shortest distance between two dots of the same color on the monitor. Usually given in fractions of a millimeter (mm), the dot pitch tells how -sharp‖ the picture is. The lower the number, the closer together the pixels are, and, thus, the sharper the image. An average dot pitch is 0.28mm. Anything smaller than 0.28mm is considered great.

Liquid Crystal Displays (LCD)

Portable computers were originally designed to be compact versions of their bigger brothers. They crammed all the components of the big desktop computers into a small, suitcase-like box called a portable computer. No matter what the designers did to reduce the size of the computer, the display remained as large as the desktop version's. That is, until an inventor found that when he passed an electric current through a semi crystalline liquid, the crystals aligned themselves with the current. It was found that by combining transistors with these liquid crystals, patterns could be formed. These patterns could represent numbers or letters. The first application of these liquid crystal displays (LCD) was the LCD watch.

Printers printers

Printers are considered standard PC components; they are often bundled with computers and sold to consumers as part of a complete package. The most common addons, printers are manufactured in several popular forms. Like other devices, each type has unique advantages and disadvantages.

A printer is a device that prints text or illustrations on paper, transparent sheets, etc

Three of the most commonly used printers are Dot matrix Ink jet Laser jet

Portable systems

PCMCIA content to be removed & would be better if it is added in the expansion slots in Motherboard module

Dot-Matrix Printers Ink-Jet Printers

A quick trip through a consumer electronics store might lead the average person to believe the age of the dot-matrix printer is over. The home and home office segments of the market are now the domain of the ink-jet and low-cost laser products. Still, in business locations, where the ability to print several copies at once is a driving factor, the loud and lowly dot-matrix still rules.

Ink-jet printers spray ink onto paper to form images. They produce good-quality printing and-compared to dot-matrix and wax printers-they are relatively fast. They also require little maintenance beyond cleaning and ink cartridge replacement. Their ability to easily produce color as well as standard black-and-white images makes them attractive.

Laser Printers

The laser printer has become the dominant form of computer output device, with models ranging from personal, low-volume, desktop printers to behemoths that fill half a room and serve hundreds of users, churning out reams of pages every day.

All laser printers follow one basic engine design, similar to the one used in most office copiers. They are non impact devices that precisely place a fine plastic powder (the toner) on paper. Although they cost more to purchase than most ink-jet printers, they are much cheaper to operate per page, and the "ink" is permanent.

Printers Printer Connection

There are eight major Printer connection types: serial, parallel, Universal Serial Bus (USB), network, infrared, SCSI, IEEE 1394, and wireless. You've learned about these connections earlier, but now you will learn how they apply to printers.

Serial Parallel

When computers send data serially, they send it one bit at a time, one after another. The bits stand in line like people at a movie theater, waiting to get in. Just as with modems, you must set the communication parameters (baud, parity, start and stop bits) on both entities-in this case, the computer and its printer(s)-before communication can take place.

When a printer uses parallel communication, it is receiving data eight bits at a time over eight separate wires (one for each bit). Parallel communication is the most popular way of communicating from computer to printer, mainly because it's faster than serial.

A parallel cable consists of a male DB-25 connector that connects to the computer and a male 36-pin Centronics connector that connects to the printer. Most of the cables are less than 10 feet long.

Universal Serial Bus (USB)

The most popular type of printer interface as this book is being written is the Universal Serial Bus (USB). In fact, it is the most popular interface for just about every peripheral. The convenience for printers is that it has a higher transfer rate than either serial or parallel and it automatically recognizes new devices.

Network

Some of the newer printers (primarily laser and LED printers) have a special interface that allows them to be hooked directly to a network. These printers have a network interface card (NIC) and ROM-based software that allow them to communicate with networks, servers, and workstations.

The type of network interface used on the printer depends on the type of network the printer is being attached to. For example, if you're using a Token Ring network, the printer should have a Token Ring interface.

SCSI

Only a few types of printers use SCSI interfaces to the PC, and most of them are laser printers, dye-sublimation printers, or typesetters. When these printers were introduced, they all came with an option for a SCSI interface.

The benefits in these situations were: There could be more than one device on a single SCSI connection through daisy chaining.

It was fairly simple to implement. It had relatively large throughput compared to other interfaces of the time.

Because of the advent of higher-speed peripheral connection methods, like IEEE 1394/Fire Wire and USB 2.0, SCSI interfaces for printers are rapidly becoming obsolete.

IEEE 1394 Fire Wire Wireless

The IEEE 1394 interface (also known as Fire Wire-an Apple trademark) has had an explosion of popularity recently. This interface has a maximum throughput of 800MBps, so more and more devices that need to send a lot of data in a short period of time will use this interface. Printers used for tasks such as graphics and typesetting that need to receive hundreds of megabytes of camera-ready art and graphics have IEEE 1394 ports. Not many home printers use IEEE 1394.

The latest boom in printer interface technology is wireless (of many different kinds).

With the advent of IEEE 802.11b wireless networking it is possible for people to roam around an office and still remain connected to each other and to their corporate network. So, someone had the idea that it would be nice if printers could be that mobile as well. Some printers either have built in 802.11b interfaces or are hooked to 802.11b bridges with their built-in network cards. Another wireless technology that has been gaining acceptance rapidly, especially among peripheral manufacturers, is Blue tooth. Blue tooth is a wireless technology that is used to replace the myriad of interface cables that run between your computer and all its peripherals. It's not meant to work over long distances (its absolute maximum range is 100 meters, and most devices are specified to work within 10 meters).

Printers like the HP 955c have Blue tooth capability.

When printing with a Blue tooth-enabled device (like a PDA or cell phone) and a

Blue tooth-enabled printer, all you need to do is get within range of the device (i.e. move closer), select the print driver from the device, and select -print‖. The information is transmitted wirelessly, through the air using radio waves, and is received by the device.

Modem

Modem (from modulator-demodulator)

How Modems work ?

A modem modulates outgoing digital signals from a computer or other digital device to analog signals for a conventional copper twisted pair telephone line and demodulates the incoming analog signal and converts it to a digital signal for the digital device.

Types of modem

Dial up Modem

The client uses a dial up modem connected to a computer and a telephone line to dial into an Internet Service Provider's (ISP) node, which is then routed to the Internet.These modems utilize traditional copper phone lines to transmit analog signals. The maximum speed delivered by a dial up modem is 56 Kbps. Dial up modems can be installed inside a PC in an expansion slot or attached to the PC externally through a serial or USB port.

Internal Dial up modem

As the name suggests, this type of dial up modem is installed inside a PC in an expansion slot. It has 2 RJ11 ports -one connected to the line and the other connected to the phone.

Cable Modem

A cable modem is a type of modem that provides access to a data signal sent over the cable television infrastructure.Because the coaxial cable used by cable TV provides much greater bandwidth than telephone lines, a cable modem can be used to achieve extremely fast access to the internet.

DSL Modem

DSL (Digital Subscriber Line) is a very high-speed connection that uses the same cables as a regular telephone line. Unlike dial up modem, both the internet and the phone (for calls) can be used at the same time.

Portable Systems

Laptop Architecture

Laptop Architecture Laptops are similar to desktop computers in architecture in that they contain many parts that perform similar functions. However, the parts that make up a laptop are completely different from those in desktop computers. They are physically much smaller and lighter, and they must fit into the compact space of a laptop's case. Also, laptop parts are designed to consume less power and to shut themselves off when not being used (although many desktops have so me components that go into a low-power state when not active, such as video circuitry). Finally, most laptop components (especially the motherboard) are proprietary-the LCD screen from one laptop will not necessarily fit on another.

Comparing Laptops to Desktops

If you've ever shopped for a laptop, you have no doubt noticed that the prices of desktop PCs keep dropping, whereas the prices of notebook computers stay about the same. If you've ever wondered what makes a laptop so much different than a PC, here are the primary differences between lapto ps and desktops:

Portability

This is probably the most obvious difference. Laptops are designed to be portable. They run on batteries, so you aren't tied to one spot at home or at the office. Networking options are now available that allow you to connect to a network wirelessly and do work from just about anywhere, including malls, airports and so on. As anyone who's tried to bring their full-tower PC to a LAN party can tell you, desktops just aren't that portable.

Cost

Laptops cost more-sometimes as much as 60 to 80 percent more-than similar desktop computers with similar features. The primary reason is that portability requires small components and unique (proprietary) designs for those components so they fit into the small size necessary. Miniature versions of components cost more money than standard size (desktop) versions.

Building Your Own Performance

You can't build your own laptop. Because laptop components are designed to fit exacting specifications to fit properly inside the notebook, there generally are no universal motherboards, video boards, and so on for laptops. Memory and hard drives are the exception. You can get different brands of memory and hard drives for laptops, but you can't buy a motherboard from one company and the video circuitry from another. Even things as mundane as floppy drives are designed to work only with a specific model.

By and large, laptops are always going to loose out somewhere in the performance department. Because compromises have to be made between performance and portability, performance is what usually suffers. While it is possible to have laptops with comparable performance to a desktop, the amount of money one would have to spend for a "desktop replacement" laptop is considerable. This is not to say that a laptop can't outperform a laptop, it's just that the "bang for the buck" factor is higher in a desktop.

Expandability

Because desktop computers were designed to be modular, their capabilities can be upgraded quite easily. It is next to impossible to upgrade the processor or motherboard on most laptops.

Quality of Construction

Considering how much abuse laptops get, it is much more important that the materials construction of the laptop case and other components be extremely durable. Not that it isn't important in a desktop-but it's more important in a laptop.

Portable Systems ( Components of a Laptop) Laptop Case

A typical laptop case is made up of three main parts: the display(usually an LCD display), the case frame(the metal reinforcing structure inside the laptop that provides rigidity and strength and that most components mount to), and the laptop's case itself (the plastic cover that surrounds the components and provides protection from the elements).

Motherboard and Supporting Circuitry

The motherboard of a laptop is the backbone structure to which all internal components connect. However, with a laptop, almost all components are integrated onto the motherboard, including onboard circuitry for the serial, parallel, USB, IEEE 1394, video, expansion, and network ports of the laptop.

Memory Storage

Notebooks don't use standard desktop computer memory chips. In fact, until fairly recently, there were no standard types of memory chips. If you wanted to add memory to your laptop, you had to order it from the laptop manufacturer (and usually pay a premium over and above a similar-sized desktop memory chip).

Displays

Laptops normally use liquid crystal displays (LCD) that are integrated into the case. These LCD displays are designed to consume less power and be more portable than other display types.

A laptop's display takes the most power to run. It is also the device that drains the battery the fastest when the laptop is running on batteries only. Because the technology behind LCD displays is complex, there are almost no service procedures for the display in a laptop. Most often, when the display is broken, it can be removed by a service technician (usually the display is only held in with a few screws and a plastic bezel) and exchanged with the manufacturer for a new one. This procedure may be under warranty (depending on the length of the manufacturer's warranty). One particular sore spot with laptop owners and manufacturers is the phenomenon known as bad pixels( Bad Pixels happens when a particular matrix in display goes bad).

Input Devices Keyboards

A standard-size desktop keyboard wasn't designed to be portable. It wouldn't fit well with the portable nature of a laptop. That usually means laptop keys are not normal size; they must be smaller and packed together more tightly. People who learned to type on a typewriter or regular computer often have a difficult time adjusting to a laptop keyboard because the keys are smaller and closer together. Laptop keyboards are built into the lower portion of the cl amshell. Sometimes, they can be removed easily to access peripherals below them (like memory and hard drives, as in the IBM Think pad series). Because of the much smaller space available for keys, some laptop keys (like the number pad, Home, Insert, PgUp, and PgDn keys) are consolidated into special multifunction keys. These keys are accessed through the standard keys by using a special function key (usually labeled Fn).

Mice and Pointing Devices

In addition to the keyboard, you must have a method of controlling the on-screen pointer in the Windows interface. There are many methods of doing this, but the most common are as follows:

Trackball Touch pad Touch point

Touch screen

Most laptops today include a mouse/keyboard port, a USB port, or both. Either of these ports can be used to add an input device like a mouse or a standard-sized keyboard.

PCMCIA (PC Card) Expansion Bus

PCMCIA's bus width is either 16-bit or 32-bit, as discussed. Also, PC Cards support only one IRQ (a problem if you need to install in a PC Card bus two devices that both need interrupts). PC Cards also do not support bus mastering or Direct Memory Access (DMA). However, because of its flexibility, PCMCIA has quickly become a very popular bus for all types of computers (not just laptops).

Three major types of PC Cards (and slots) are in use today. Each has different uses and physical characteristics. Coincidentally, they are called Type I, Type II, and Type III:

Type I cards are 3.3mm thick and are most commonly used for memory cards. Type II cards are 5mm thick and are mostly used for modems and LAN adapters. This is the most common PC Card type found today, and most systems have at least two Type II slots (or one Type III slot).

The Type III slot is 10.5mm thick. Its most common application is PC Card hard disks. Developers have been slowly introducing these devices to the market.

In addition to the card, the PC Card architecture includes two other components:

Socket Services software is a BIOS-level interface to the PCMCIA bus slot. When loaded, it hides the details of the PC Card hardware from the computer. This software can detect when a card has been inserted and what type of card it is.

Card Services software is the interface between the application and Socket Services. It tells the applications which interrupts and I/O ports the card is using. Applications that need to access the PC Card don't access the hardware directly; instead, they tell Card Services that they n eed access to a particular feature, and Card Services gets the appropriate feature from the PC Card.