MODULE 2

Expansion cards

The expansion card(also expansion board,adapter card oraccessory card) in

computing is a printed circuit board that can be inserted into an expansion slot of a

computer motherboardor backplane to add functionality to a computer system via

the expansion bus.

One edge of the expansion card holds the contacts (the edge connector) that fit

exactly into the slot. They establish the electrical contact between the electronics

(mostlyintegrated circuits) on the card and on the motherboard.

Connectors mounted on the bracket allow the connection of external devices to the

card. Depending on the form factor of the motherboard and case, around one to

seven expansion cards can be added to a computer system. 19 or more expansion

cards can be installed in backplane systems. There are also other factors involved

in expansion card capacity. For example, most graphics cards on the market as of

2010 are dual slot graphics cards, using the second slot as a place to put an

activeheat sink with a fan. The first commercial microcomputerto feature

expansion slots was the Micral N, in 1973.

1)VIDEO CARDS

Avideo card (also called a video adapter,display card,graphics card, graphics

board,display adapter or graphics adapter) is an expansion card which generates a

feed of output images to a display. Most video cards offer various functions such

as accelerated rendering of 3Dscenes and2D graphics, MPEG-2/MPEG-4

decoding, TV output, or the ability to connect multiple monitors (multi-monitor).

Video hardware can be integrated into the motherboard or (as with more

recentdesigns) the CPU, but all modern motherboards (and some from the 1990s)

provideexpansion ports to which a video card can be attached. In this configuration

it issometimes referred to as a video controller or graphics controller. Modern low-

endto mid-range motherboards often include a graphics chipset manufactured by

the developer of the Northbridge(e.g. an AMDchipset with Radeongraphics or an

Intel chipset with Intel graphics) on the motherboard. This graphics chip usually

has a small quantity of embedded memory and takes some of the system's main

RAM, reducing the total RAM available. This is usually called integrated graphics

oron-board graphics, and is usually low in performance and undesirable for those

wishing to run 3D applications. A dedicated graphics card on the other hand has its

own Random Access Memory or RAM and Processor specifically for processing

video images, and thus offloads this work from the CPU and system RAM A

modern video card consists of a printed circuit board on which the components are

mounted. These include:

a)Graphics processing unit

A GPU is a dedicated processor optimized for accelerating graphics. The processor

is designed specifically to perform floating-point calculations, which are

fundamental to 3D graphics rendering and 2D picture drawing. The main attributes

of the GPU are the core clock frequency, which typically ranges from 250 MHz to

4 GHz and the number of pipelines (vertex and fragment shaders), which translate

a 3D image characterized by vertices and lines into a 2D image formed by pixels

Modern GPUs are massively parallel, and fully programmable. Their computing

power is orders of magnitude greater than that of CPUs for certain kinds of

operations. This has led to the emergence of general-purpose computing

ongraphics processing units.

b)Heat Sink

Aheat sink is mounted on high performance graphics cards. A heat sink spreads out

the heat produced by the graphics processing unit evenly throughout the heat sink

and unit itself. The heat sink commonly has a fan mounted as well to cool the heat

sink and the graphics processing unit.

c)Video BIOS

The video BIOS or firmware contains the basic program, which is usually hidden,

that governs the video card's operations and provides the instructions that allow the

computer and software to interact with the card. It may contain information on the

memory timing, operating speeds and voltages of the graphics processor, RAM,

and other information. It is sometimes possible to change the BIOS (e.g. to enable

factory-locked settings for higher performance), although this is typically only

done by video card over lockers and has the potential to irreversibly damage the

card.

d)Video memory

The memory capacity of most modern video cards ranges from 128 MB to 8 GB.

Since video memory needs to be accessed by the GPU and the display circuitry, it

often uses special high-speed or multi-port memory, such as VRAM, WRAM,

SGRAM, etc. Around 2003, the video memory was typically based on

DDRtechnology. During and after that year, manufacturers moved towards

DDR2,GDDR3,GDDR4 and GDDR5. The effective memory clock rate in modern

cards is generally between 1 GHz and 6.3 GHz

e)RAMDAC

The RAMDAC, or Random Access Memory Digital-to-Analog Converter,

converts digital signals to analog signals for use by a computer display that

usesanalog inputs such as Cathode ray tube(CRT) displays. The RAMDAC is a

kind of RAM chip that regulates the functioning of the graphics card. Depending

on the number of bits used and the RAMDAC-data-transfer rate, the converter will

be able to support different computer-display refresh rates. With CRT displays, it

is best to work over 75 Hz and never under 60 Hz, in order to minimize flicker.

(With LCD displays, flicker is not a problem.) Due to the growing popularity of

digital computer displays and the integration of the RAMDAC onto the GPU die, it

has mostly disappeared as a discrete component. All current LCDs, plasma

displays and TVs work in the digital domain and do not require a RAMDAC

f)Outputs

Video In Video Out (VIVO) for S-Video (TV-out), Digital Visual Interface (DVI)

for High-definition television (HDTV), and DB-15 for Video Graphics Array

(VGA)

1)Video Graphics Array (VGA)

Analog-based standard adopted in the late 1980s designed for CRT displays, also

called VGA connector. Some problems of this standard are electrical noise,image

distortion andsampling errorevaluating pixels.

2)Digital Visual Interface (DVI)

Digital-based standard designed for displays such as flat-panel displays (LCDs,

plasma screens, wide high-definition television displays) and video projectors.

Insome rare cases high end CRT monitors also use DVI. It avoids image distortion

and electrical noise, corresponding each pixel from the computer to a display pixel,

using itsnative resolution. It is worth to note that most manufacturers include DVI-

connector, allowing(via simple adapter) standard RGB signal output to an old CRT

or LCD monitor with VGA input.

3)Video In Video Out (VIVO

Included to allow the connection with televisions,DVD players,video recorders

andvideo game consoles. They often come in two 10-pin mini-DIN

connectorvariations

4)High-Definition Multimedia Interface (HDMI)

An advanced digital audio/video interconnect released in 2003 and is commonly

used to connect game consoles and DVD players to a display.

2)SOUND CARD

Asound card (also known as an audio card) is an internal computer expansion

cardthat facilitates the input and output of audio signals to and from a computer

under control of computer programs. The term sound cardis also applied to

external audio interfaces that use software to generate sound, as opposed to using

hardware inside the PC. Typical uses of sound cards include providing the audio

component for multimedia applications such as music composition, editing video

or audio, presentation, education and entertainment (games) and video projection.

Sound functionality can also be integrated onto the motherboard, using basicallythe

same components as a plug-in card. The best plug-in cards, which use betterand

more expensive components, can achieve higher quality than integrated sound. The

integrated sound system is often still referred to as a "sound card".Most sound

cards use a digital-to-analog converter(DAC), which converts recorded or

generated digital data into an analog format. The output signal is connected to an

amplifier, headphones, or external device using standard interconnect. If the

number and size of connectors is too large for the space on the back plate the

connectors will be off-board, typically using a breakout box, an auxiliary back

plate, or a panel mounted at the front. More advanced cards usually include more

than one sound chip to support higher data rates and multiple simultaneous

functionalities. Most sound cards have a line in connector for an input signal from

a cassette tape or other sound source that has higher voltage levels than a

microphone. The sound card digitizes this signal. The DMACtransfers the samples

to the main memory, from where a recording software may write it to the hard disk

for storage, editing, or further processing. Another common external connector is

the microphone connector, for signals from a microphone or other low-level input

device.

An important sound card characteristic is polyphony, which refers to its ability to

process and output multiple independentvoices or soundssimultaneously. These

distinctchannels are seen as the number of audio outputs, which may correspond to

a speaker configuration such as 2.0 (stereo), 2.1 (stereo and sub woofer), 5.1

(surround), or other configuration. Sometimes, the terms voice and channel are

used interchangeably to indicate the degree of polyphony, not the output speaker

configuration.

3)NETWORK INTERFACE CARD (NIC)

A network interface card (also known as a network interface card, network

adapter, LAN adapter and by similar terms) is a computer hardware component

that connects a computer to a computer network.

Early network interface controllers were commonly implemented on expansion

cards that plugged into a computer bus; the low cost and ubiquity of the Ethernet

standard means that most newer computers have a network interface built into the

motherboard. The network controller implements the electronic circuitry required

to communicate using a specific physical layer and data link layer standard such as

Ethernet,Wi-Fi, orToken Ring. This provides a base for a full network protocol

stack, allowing communication among small groups of computers on the same

LANand large-scale network communications through routable protocols, such as

IP.

Every Ethernet network controller has a unique 48-bit serial number called a MAC

address, which is stored in read-only memory. Every computer on an Ethernet

network must have at least one controller. Normally it is safe to assume that no two

network controllers will share the same address, because controller vendors

purchase blocks of addresses from the Institute of Electrical and Electronics

Engineers (IEEE) and assign a unique address to each controller at the time of

manufacture.

The NIC allows computers to communicate over a computer network. It is both an

OSI layer 1 (physical layer) and layer 2 (data link layer) device, as it provides

physical access to a networking medium and provides a low-level addressing

system through the use of MAC addresses. It allows users to connect to each other

either by using cables or wirelessly.

ROM (READ ONLY MEMORY)

Read-only memory (ROM) is a class ofstorage medium used in computers and

other electronic devices. Data stored in ROM cannot be modified, or can be

modified only slowly or with difficulty, so it is mainly used to distribute firmware

(software that is very closely tied to specific hardware, and unlikely to need

frequent updates).

In its strictest sense, ROM refers only to mask ROM(the oldest type of solid state

ROM), which is fabricated with the desired data permanently stored in it, and thus

can never be modified. Despite the simplicity, speed and economies of scale of

mask ROM,field-programmability often make reprogrammable memories more

flexible and inexpensive. Other types ofnon-volatile memorysuch 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. When used in this less precise way, "ROM" indicates a non-volatile

memory which serves functions typically provided by mask ROM, such as storage

of program code and nonvolatile data.

Everystored-program computer needs some form of non-volatile storage (that is,

storage that retains its data when power is removed) to store the initial program

that runs when the computer is powered on or otherwise begins execution (a

process known as bootstrapping, often abbreviated to "booting" or "booting up").

Likewise, every non-trivial computer needs some form of mutable memory to

record changes in its state as it executes.

In modern PCs, "ROM" (or flash) is used to store the basic

bootstrapping firmware for the main processor, as well as the

various firmware needed to internally control self contained devices such

as graphic cards,hard disks,DVD drives,TFT screens, etc., in the system. Today,

many of these "read-only" memories – especially the BIOS – are often replaced

with Flash memory (see below), to permit in-place reprogramming should the need

for a firmware upgrade arise. However, simple and mature sub-systems (such as

the keyboard or some communication controllers in the ICs on the main board, for

example) may employ mask ROM or OTP(one time programmable)

Programmable read-onlymemory(PROM), or one-time programmable

ROM (OTP), can be written to or programmed via a special device called

a PROM programmer. Typically, this device uses high voltages to

permanently destroy or create internal links (fuses or antifuses) within the chip. Consequently, a PROM can only be programmed once.

Erasable programmable read-only memory (EPROM)

can be erased byexposure to strong ultraviolet light (typically for 10 minutes or

longer), then rewritten with a process that again needs higher than usual voltage

applied. Repeated exposure to UV light will eventually wear out an EPROM, but

the endurance of most EPROM chips exceeds 1000 cycles of erasing and

reprogramming. EPROM chip packages can often be identified by the prominent

quartz "window" which allows UV light to enter. After programming, the window

is typically covered with a label to prevent accidental erasure. Some EPROM chips

are factory-erased before they are packaged, and include no window; these are

effectively PROM.

Electrically erasable programmable read-only memory (EEPROM) is based

on a similar semiconductor structure to EPROM, but allows its entire contents

(or selected banks) to be electrically erased, then rewritten electrically, so that

they need not be removed from the computer (or camera, MP3 player, etc.).

Writing or flashing an EEPROM is much slower (milliseconds per bit) than

reading from a ROM or writing to a RAM (nanoseconds in both cases).

Electrically alterable read-only memory (EAROM) is a type of EEPROM

that can be modified one bit at a time. Writing is a very slow process and

again needs higher voltage (usually around 12 V) than is used for read

access. EAROMs are intended for applications that require infrequent and

only partial rewriting. EAROM may be used as non-volatile storage for

critical system setup information; in many applications, EAROM has been

supplanted byCMOS RAM supplied bymains power and backed-up with a

lithium battery.