4 Monitor&Videocard

7/27/2019 4 Monitor&Videocard

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Monitors

&

Video Cards

Supporting I/O Devices


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PC Displays

CRT- Cathode Ray Tube

A CRT monitor uses a vacuum tube

to contain the beam of electrons used

to produce the image

Two Types:

RegularFlat-technology monitors


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PC Displays

Flat panel monitors are built to receive either an

analog signal or a digital signal from the video card

and have two ports on the monitor to accommodate

either signal

Flat Panel Technology

LCD : Liquid Crystal Display

PDP: Plasma Display PanelA gas plasma display

ELD: Electroluminescent display

LED: Light Emitting Diode


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Display Subsystem

Each PCs display subsystem consists

of three parts:

Video Display Adapter

creates and holds the image information

Monitor

displays the information

Cable

connects the video adapter to the

monitor


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Display Basics

Pixels

In a CRT display device, the smallestpossible pixel is actually a dot triocalled a triad

a red, green and blue phosphor dotset

RGB Model - most common modelfor PC video displays


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Display Basics

An electronic beam is used to strike the

phosphor causing it to emit light

Plates on the top, bottom and sides of the

CRT tube control the direction of the beam Depending on the intensity of the beam, the

dot trio emits a range of colors created by

mixing the 3 colors: red, blue and green


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Computer Display Systems

CRT- Cathode Ray tube- the same

technology employed by your television- an

electron gun scans the screen causing

special chemicals called phosphors to glow-the gun scans from top to bottom, left to right

Video Adapter- an expansion board or

integrated device that renders characters for

display in response to commands from thecomputer- it tells the display device how to

draw the graphic


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Video Technologies

Monochrome- two color video- text only with a resolution of 720x 350

Color Graphics Adapter- CGA- four colors- 320 x 200 resolutionfor graphics, 640 x 200 for two color

Enhanced Graphics Adapter- EGA- 16 colors- 320 x 200graphics, 640 x 350 text

Video Graphics Array- VGA- introduced with the IBM AT formfactor motherboards- used an analog signal- 256KB of videomemory on board- 16 colors at 640 x 480 or 256 colors at 320 x200

Super Video Graphics Array- introduced by the VideoElectronics Standards Association- 65, 536 colors at 640 x 480,

256 colors at 800 x 600 or 16 colors at 1,024 x 768 Extended Graphics Array- IBMs answer to the SVGA, XGA

could only use the MCA expansion bus- it also used interlacing,or scanning every other line on each pass- offered the sameresolution options as the SVGA


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Display Quality Measurements

Dot Pitch- the shortest distance between two

dots of the same color on the monitor

Measured in millimeters

The lower the number, the sharper the image .28mm is considered average- anything smaller is

great

Refresh Rate- vertical scan frequency- how

many times in one second does the electronbeam redraw the screen? The standard is

60Hz for VGA


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Displays

Most desktop displays use acathode ray tube (CRT),while portable computingdevices such as laptopsincorporate liquid crystaldisplay (LCD)

Because of their slimmerdesign and smaller energyconsumption, monitors usingLCD technologies arebeginning to replace the

venerable CRT on manydesktops


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CRT Monitor

How a CRT monitor works


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DAC Converters

Digital-to-Analog (DAC) Converters

special integrated circuits used by

display adapters


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Two Ways to Paint Image on Screen:

Vector Displays

the electronic beam used to create

the image is moved across the

screen in a pattern similar to moving

a pen or pencil over a piece of paper


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Two Ways to Paint Image on Screen:

Raster-Scan

the screen is painted line by line from leftto right

the electronic beam is played across thescreen from left to right in a straighthorizontal line - moves to left and goes tonext line

Most CRTs and LCDs use Raster-Scanto paint images to screen


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Liquid Crystal Displays

Active Matrix- each LCD pixel has a transistorbehind it to activate or deactivate the crystal Very crisp and easy on the eyes

Very power intensive- severely limited the amount of time alaptop could run on battery power

Passive Matrix- two rows of transistors marking the xand y coordinates of a grid- a signal voltage line issent to the x and y coordinates, turning thecorresponding pixel dark Requires less power

Sacrifices image quality Response of the screen to rapid change is poor


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LCD panels

An LCD is made with eithera passive matrix or an activematrix display display grid

The passive matrix LCD,which is older technology,has a grid of conductors

with pixels located at eachintersection in the grid.

The active matrix LCD isalso known as a thin filmtransistor (TFT) display,which has a transistor

located at each pixelintersection, requiring lesscurrent to control theluminance of a pixel.


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LCD panels

A color LCD must havethree subpixels with red,green and blue color filtersto create each color pixel

Through the careful control

and variation of the voltageapplied, the intensity of eachsubpixel can range over 256shades

Combining the subpixelsproduces a possible palette

of 16.8 million colors


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LCD technology

LCDs today employ several variations of

liquid crystal technology, e.g. ferroelectric

liquid crystal (FLC)

Display size is limited by the quality-control problems faced by manufacturers

The more transistors that are put in display,

the chances are that the will be defective

Manufacturers of existing large LCDs oftenreject about 40 percent of the panels that

come off the assembly line


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LCD Monitors

In general, an LCD panel is made of two polarized

planes of glass placed at right angles (90 degrees) to

each other.

Sandwiched between the glass is a layer of liquid

crystals. Behind the back panel is a fluorescent light source that

tries to get through the two misaligned panels of glass.

In the default state, the light is blocked, and the panels

appear black. Unless there is a light behind the panel or a very bright

light reflecting through the front panel and then off the

back panel, an LCD cannot display anything.


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LCD Monitors

The LCD monitors use the CMY (cyan,magenta, yellow) process of building colors

Triads of three crystals (each being able to

pass only one primary color) are put togetherin a matrix

By turning on one of the crystals in each triad

the same effect can be produced as with an

electron beam and phosphorus in the CRT

monitors


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LCD Monitors

Each liquid crystal is in a matrix or grid(rows and columns) with very thin wiresleading to a set of of switches along the

top and side edges of the glass panelsWhen electric current is sent to a

specific X-Y location on the grid, theliquid crystal is activated

LCD monitors can be passive matrix oractive matrix


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LCD Monitors

Passive Matrix

One transistor switch per row and column

That is, for an 640x480 VGA LCD panel,

the monitor requires 640 transistorswitches along the side and 480 transistor

switches along the top to produce the

640x480 pixels or dots of light


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LCD Monitors

Active Matrix The fundamental difference between the

passive matrix and the active matrix is thenumber of transistor switches on the panel:

The active matrix gives every liquidcrystal its own switch.

This speeds up the process of

pinpointing a specific X-Y co-ordinateand also provides greater control overthe crystal.


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LCD Monitors

The three main types of active-matrix

LCD panels are:

TFT - Thin Film Transistors

MIM - Metal-Insulator-Metal

PALC - Plasma Addressed Liquid

Crystal


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Maximum Resolution and Dot Pitch

Resolution refers tothe number of individual

dots of color, known as

pixels, contained on a

display. Resolution istypically expressed by

identifying the number

of pixels on the

horizontal axis (rows)

and the number on the

vertical axis (columns),

such as 640x480

Dot Pitch is themeasure of howmuch space thereis between adisplay's pixels.

When consideringdot pitch, rememberthat smaller isbetter. Packing thepixels closer

together is.fundamental toachieving higherresolutions


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Resolution

For both monitors and printers we are

interested in the resolution how small are

the pixels (tiny dots)?

Typical monitors have 640 480 or 800 600

with a screen size of 15-17 inches (measured

diagonally).

For printers the resolution is in pixels or dots

per inch, typically 600 dpi for a laser printer.


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Refresh Rate

In monitors based on CRT technology, therefresh rate is the number of times that the

image on the display is drawn each second.

Refresh rates are very important because they

control flicker, and you want the refresh rate ashigh as possible.

Too few cycles per second and you will notice a

flickering, which can lead to headaches and eye

strain.


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Color Depth

The combination of the display modes supported byyour graphics adapter and the color capability of your

monitor determine how many colors can be displayed.

For example, a display that can operate in SVGA mode

can display up to 16.8 million colors because it can

process a 24-bit-long description of a pixel. The numberofbits used to describe a pixel is known as its bit depth.

With a 24-bit bit depth, 8 bits are dedicated to each of the

three additive primary colors -- red, green and blue. This

bit depth is also called true colorbecause it can produce

the 10,000,000 colors discernible to the human eye Simply put, color bit depth refers to the number of bits

used to describe the color of a single pixel. The bit depth

determines the number of colors that can be displayed at

one time
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Color Depth Chart

Bit-Depth Number of Colors

1 2

(monochrome)

2 4

(CGA)

4 16

(EGA)

8 256

(VGA)

16 65,536

(High Color, XGA)

24 16,777,216

(True Color, SVGA)

32 16,777,216

(True Color + Alpha Channel)

2


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Things to Consider

Display technology - Currently, the choices aremainly between CRT and LCD technologies.

Cable technology - VGA and DVI are the two mostcommon.

Viewable area (usually measured diagonally)

Aspect ratio and orientation (landscape or portrait) Scan or Refresh Rate

Interlace Features

Dot pitch

Resolution Color depth

Amount of power consumption


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Features

Two measures describe the size of yourdisplay:

The aspect ratio and the screen size.

Aspect Ratio: Most computer displays, likemost televisions, have an aspect ratio of 4:3

This means that the ratio of the width of the

display screen to the height is 4 to 3.

Screen Size

How to Measure

Desktop vs. Laptop


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Features

Scan or Refresh Rate, or vertical scan rate The time it takes for the electronic beam to fill the

screen with lines from top to bottom

The number of times that the image on the

display is drawn each second. If your CRT monitor has a refresh rate of 72 Hertz

(Hz), then it cycles through all the pixels from top to

bottom 72 times a second.

Control flickerYou want the refresh rate as high as possible

Standard rate established by the Video Electronics

Standards Association (VESA) is 70Hz, or 70

refreshes per second


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Features

Multiscan Multiscan monitors support a variety of refresh

rates and can support different video cards

Fixed frequency monitors only support a single

refresh rate

Interlace features

Interlaced monitors draw a screen in 2 passes,hitting the even lines first, then the odd lines

Non-interlaced monitors draw the entire screen in

1 pass


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Features

Dot PitchThe distance between adjacent dots on the screen.

The smaller the dot pitch, the higher the quality ofthe image.

A high-quality monitor should have a dot pitch of nomore than .28mm

A display normally can support resolutions thatmatch the physical dot (pixel) size as well asseveral lesser resolutions. For example, a display with a physical grid of 1280 rows

by 1024 columns can obviously support a maximumresolution of 1280x1024 pixels but it usually also supportslower resolutions such as 1024x768, 800x600, and640x480.


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Features

Color Depth The combination of the display modes supported

by your graphics adapter and the color capability

of your monitor determine how many colors can

be displayed.

Bit Depth : The number of bits used to describe a

pixel is known as its bit depth.

For example: with a 24-bit bit depth, 8 bits are

dedicated to each of the three additive primary

colors -- red, green and blue. This bit depth is

also called true colorbecause it can produce

the 10,000,000 discernible colors.


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Bit-Depth Number of Colors

12

(monochrome)

24

(CGA)

416

(EGA)

8256

(VGA)

1665,536

(High Color, XGA)

2410,000,000

(True Color, SVGA)

3216,777,216

(True Color + Alpha Channel)


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Features

Power consumption Varies greatly with different technologies.

CRTs are somewhat power-hungry, at about 110watts for a typical display, especially whencompared to LCDs, which average between 30

and 40 watts. Green monitor

In a typical home computer setup with a CRT-based display, the monitor accounts for over 80percent of the electricity used!

Monitor that meets the EPA Energy Star program Uses 100 to 150 watts of electricity with no more

than 30 watts being used when the screen saveris on


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Monitors

Feature Description

Screen Size Typically 14, 15, 17 or 21 inch - refers to diagonal length

of the lighted screen. It is often shorter than advertised.

Refresh Rate Vertical scan rate - time it takes an electronic beam to

fill screen. Should be minimum of 70Hz (70 times/sec.)

Interlaced Only refreshes half the screen on every pass.

Dot Pitch Distance between adjacent dots. Ex: .28mm

The smaller the pitch, the higher the quality.

Resolution How many spots or pixels are on screen. Ex: 640 x 480

Multiscan Monitors that offer a variety of refresh rates.

Green Monitor Supports EPA Energy Star program, uses no more than

30 watts and can go into sleep mode after inactivity.

Some Features of a Monitor


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Monitors

ELF (extremely low frequency)emissions

When matching a monitor to a videocard, consider matching a

14-inch monitor with a low-end video card

15-inch monitor with a midrange card

17-inch or larger monitor with a high-endcard for best performance

Di l Ad


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Display Adapter or

Graphics Card Creates and holds the image information Older technology: specialized circuitry on the system

board

Newer technology: a Plug-In Card- often referred toas the PCs Video Card

Graphics cards are known by many names, such as: Video cards

Video boards

Video display boards

Graphics boards Graphics adapter cards

Video adapter cards

Graphics Accelerators


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Display Adapter Standards

IBM original: MDA - Monochrome DisplayAdapter

MGA - Monochrome Graphic Adapter

CGA - Color Graphics Adapter 1981 IBM - 4 colors

EGA - Enhanced Graphics Adapter 1984 - IBM integrated color and monochrome

systems 16 colors


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VGA - Video Graphics Array

1987 - IBM

VGA became the industry standard and

further extensions were developed: SVGA - Super VGA

AVGA - Accelerated VGA - supports

Windows Graphics

XGA Extended Graphics Array

1990 - IBM


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UXGA - Ultra Extended Graphics Array

Most displays sold today support the

UXGA standard.

UXGA can support a palette of up to 16.8million colors and resolutions of up to

1600x1200 pixels, depending on the video

memory of the graphics card in your

computer


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A typical UXGA adapter takes the digital data sent by application

programs

stores it in video random access memory(VRAM) or some equivalent

uses a digital-to-analog converter (DAC) toconvert it to analog data for the display

scanning mechanism Once it is in analog form, the information is

sent to the monitor through a VGA cable.


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DVI Digital Video Interface Since today's VGA adapters do not fully

support the use of digital monitors, a newstandard, Digital Video Interface (DVI) hasbeen designed for this purpose.

DVI keeps data in digital form from thecomputer to the monitor, virtuallyeliminating signal loss (degradation).

Will need a DVI monitor with a DVIcompliant graphics card.


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Graphics/Video Card

Four basic functions of a video card


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Video Card Performance

Performance on the video card is affectedby:

Chip set

Memory

RAM DAC

Bus speed and size

Methods of improving performance

Dual-porting Place a processor on the video card to make it a

graphics accelerator


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Graphics Accelerator

A type of video card that has its ownprocessor to boost performance

Necessary with the demands that graphicapplications make in the multimedia

environment Processor is specifically designed to manage

video and graphics

Their features reduce the burden on thesystem board CPU and perform the functionmuch faster than the system board CPU


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Graphics Accelerator Features

MPEG decoding 3-D graphics

Dual porting

Color space conversion Interpolated scaling

EPA green PC support

Digital output to flat panel display monitors

Applications support for popular high-intensity graphics software


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Video Memory

Necessary to handle large volume ofdata generated by increased resolution

and color

Stored on video cards as memory chips

How Much Video Memory Is


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How Much Video Memory Is

Needed?Determined by

Screen resolution (measured in pixels)

Number of colors (color depth)

Enhancements to color information calledalpha blending


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Types of Video Memory

VRAM (video RAM)

MDRAM (multibank DRAM)

SGRAM (synchronous graphics RAM)

WRAM (Window RAM)

3D RAM

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4 Monitor&Videocard