Unit-III Display Adapters

8/9/2019 Unit-III Display Adapters

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VGA : ( video graphics array)

With the PS/2 line of computers, IBM wanted tomake more resolution colors by introducing itsbest video adapter to date: the video graphics array(VGA).

This video technology had a whopping 256KB of

video memory on board and could display 16 colorsat 640X480 pixels or 256 colors at 320X200 pixels.

It became widely used and has since become thestandard for color pc video; its the starting pointfor today's computers, as far as video is concerned.

One unique feature of VGA is that an analog board.Thus the 256 colors it uses can be chosen fromvarious shades and hues of a palette of 262,114colors.


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Super VGA :

Most video standards were set IBM. IBM made theadapters, everyone brought them, and they became

a standard

Some manufactures did not like this monopoly and

set up the video electronics standards association

(VESA) to try to enhance IBMs video technology

and make the enhanced technology a public

standard. The result of this work was super VGA.

This new standard was indeed an enhancement,

because it could support 256 colors at a resolutionof 800X600 (the VESA standard), or 1,024X768

pixels with 16 colors, or 640X with 65,536 colors


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XGA:

IBM introduced a new technology in 1991 known as the

extended graphics Array (XGA) .

This technology was only available as an Micro channel

architecture (MCA) expansion board and not as an ISA or

EISA board

XGA could support 256 colors at 1,024X768 pixels or 65,536

colors at 640X480 pixels.

It was 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


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CRTS :

The two general categories of PC visualpresentation are the

Monitor

Display

Monitor :

A monitor has a CRT [cathode raytube]

It looks like a television


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Displays :

display is a flat panel device

Egg: LCD

CRT Displays :

A CRT displays has some advantages

(1) Bright(2) Well light

(3) Produces excellent graphics

(i) The CRT is funnel shaped glass tube

(ii) That uses the electronics guns to light up phosphorelements on the back of the display glass


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CRT Display sizes :

CRT monitor sizes are given in what are called

nominal sizes

The most popular monitor sizes are 15-inch, 17

inch, 19 inch and 21 inch

The viewable size of a 17 inch CRT display isactually a bit less than 16 inches because

remaining part will be covered by the edge of the

monitor to hold the CRT in place


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Working Principal :

The primary element of the CRT, as

illustrated in the electron gun that shoots a

beam of electrons on the back of the

display screen which is used with millionsof tiny dots of a phosphorus material

The phosphor dots glow when struck by

the electrons


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CRTComponent :

Display

Electronic beams

Electronic Gun


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If you look closely at the monitors screen, you can see

these dots

Three of the phosphor dots are grouped together to form

a pixel, which is also called a traid. In each pixel, one dot

is red, one is green and one is blue in colors

How much intensity is used to light each dot of the pixel

determines the color your eye sees in the pixel

The blinding of these three colors in the basics RGBcolor, which is the color display standard used in all

monitors


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Unit-III Display Adapters

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