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Video

Overview

• In this part, you will learn to– Learn how CRT displays operate– Learn how LCD displays operate– Examine the video chipsets– Learn how to install video devices– Discuss 3D graphics accelerators– Troubleshoot video devices

Opening up a monitor can be deadly!

Even when the power is disconnected, certain components inside a monitor retain a substantial voltage for an extended period of time. If you accidentally short one of the components, it could actually kill you!

Warning

CRT and LCD Displays

Video

• Video consists of two devices - the video card (or display adapter) and the monitor

• The video card consists of two distinct components – one to take commands from the computer and update its own onboard RAM, and the other to scan the RAM and send data to the monitor

Video Monitor Types

• Cathode ray tube (CRT)• Liquid crystal display (LCD)

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CRT

• All CRT monitors have a cathode ray tube(CRT), which is a vacuum tube

• One end of this tube is a slender cylinder that consists of three electron guns

• The wide end of the CRT is the display screen

CRT

• When power is applied to one or more of the electron guns, a stream of electrons is generated

• This stream is subjected to a magnetic field generated by a ring of electromagnets called a yoke

• The phosphor coating, when struck by the electron beam, releases energy as visible light– The phospors continue to glow momentarily after

being struck – called persistence.

CRT Refresh Rates

• Horizontal Refresh Rate (HRR)– The speed at which the

electron beam moves across the screen

• Vertical Refresh Rate(VRR)– The amount of time

taken by the monitor to draw the entire screen and get the electron beam back to the start

Video data is displayed on the monitor as the electron gun sweeps the display horizontally, energizing appropriate areas onthe phosphor coating.

CRT Refresh Rates

CRT Refresh Rates

• Video cards push the monitor at a given VRR, and then the monitor determines the HRR– If the VRR is set too low, you’ll see flicker – If it is set too high, you’ll have a distorted screen

image and may damage the monitor

• Multisync (multiple-frequency monitor) monitors support multiple VRRs

Phosphors

• Phosphors and shadow mask:– Phosphors are

dots inside the CRT monitor that glow red, green, or blue when an electron gun sweeps over them

– Phosphors are evenly distributed across the front of the monitor

One group of red, green, and blue phosphors is called a triad.

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Shadow Mask

• Shadow mask is a screen that enables the proper electron gun to light the proper phosphor

• Electron guns sweep across the phosphors as a group

• The area of phosphors lit at one time by a group of guns is called a pictureelement, or pixel

Resolution

• Monitor resolution is always shown as the number of horizontal pixels times the number of vertical pixels

• Some common resolutions are 640X480, 800X600, 1024X768, 1280X1024, and 1600X1200

• These resolutions match a 4:3 ratio called the aspect ratio

Dot Pitch

• Dot pitch defines the diagonal distance between phosphorous dots of the same color. – The dot pitch can range from as high as .39 mm to

as low as .18 mm– The lower the dot

pitch, the more dots across the screen which produces a sharper, more defined image

Interlacing

• Interlacing is the process in which the monitor sweeps or refreshes alternate lines of pixels on the display– It enables a low-end monitor to support faster

refresh rates by giving it twice as much time to make a screen

– Can create eyestrain and headaches

Bandwidth

• Bandwidth defines the maximum number of times an electron gun can be turned on or off per second– Bandwidth is measured in megahertz (MHz)– How fast the monitor can put an image on the

screen

Maximum VRR = bandwidth ÷ pixels per page

For example, a 17-inch monitor with a 100MHz bandwidth and a resolution of 1024x768 can support a maximum VRR of 127 Hz:

100,000,000 ÷ (1024x768) = 127 Hz

LCDs

• Liquid Crystal Displays– Thinner and lighter– Much less power– Flicker free– Don’t emit radiation– Called Flat Panels or Flat Panel Displays

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Light

• Travels in waves• Wavelength determines the color• If light came at us in one wavelength we

would see just one color• We usually see many different

wavelengths which looks white

How LCDs Work

• Liquid crystals take advantage of the property of polarization

• These crystals are composed of specially formulated liquid, full of long, thin crystals that always orient themselves in the same direction

• The crystals act exactly like a liquid polarized filter

Liquid Crystal Molecules

• LCD monitors use liquid crystal molecules that tend to line up together– These molecules take advantage of polarization– Fine grooves in a piece of glass will cause the

molecules to line up along the grooves

Twisting Molecules

• Use two pieces of glass with fine grooves oriented at a 90° angle– Molecules in the middle will try to line up to both

sides – creating a nice twist

Add Polarizing Filters

• Now add polarizing filters to both sides– The liquid crystal will twist the light and enable it to

pass through– Adding an electrical potential will cause the crystals

to try to align to the electrical field• To darken an area, apply a charge

LCD Matrix

• Calculators use static charging to darken areas

• LCD screens use a matrix of wires to provide a charge with greater precision

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Passive Matrix

• Use three matrices to produce color• Above the intersections of the wires add

tiny red, green, and blue dots• The amount of voltage will allow

different levels of red, green, and blue

Dual-Scan Passive Matrix

• Passive matrix is slow and tends to create an overlap between pixels

• Dual-scan passive matrix is faster by refreshing two lines at a time– Still used on some lower-end LCD panels

Thin Film Transistor (TFT)

• Thin Film Transistor (TFT) is also known as the active matrix

• It uses one or more tiny transistors to control each color dot

• TFTs are brighter, with better contrast, can handle a variety of colors, and have a much wider viewing area

LCD Resolution

• LCD panels come with a fixed number of pixels, which is always equivalent to a common resolution

• LCD panels cannot display more than their pixel limitation

• Lower resolutions are faked by estimating the pixels

Backlighting

• Backlighting is needed to improve visibility

• LCD uses a type of cold fluorescent light with prisms to spread light evenly across the screen– The measurement unit nits (candela/meter2) is

used to quantify the brightness of the backlighting

Contrast Ratios

• The contrast ratio is the difference between the darkest and lightest spots a monitor can display– CRT monitors can display 450:1– LCD monitors display 250:1

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Monitor Size

• The size of CRT monitors is measured in inches

• All monitors provide two numbers - the monitor size and the actual size

• Viewable Image Size (VIS) is the measurement of the actual screen from one edge of the screen to the opposite diagonal side

• LCD monitors just use the VIS value

CRT Connections

• CRT monitors use a 15-pin, 3 row, DB type connector, and a power plug

RAMDAC

• The Random Access Memory Digital-to-Analog Converter (RAMDAC) chip converts digital signals into analog signals for analog CRTs

• LCD monitors use digital signals and need a circuitry for converting analog signals to digital (analog LCD monitor)

RAMDAC

LCD Connections

• We now see LCD monitors that use digital video cards (no RAMDAC) and a totally different Digital Video Interface (DVI) connector– DVI-A (analog)– DVI-D (digital)– DVI-A/D or DVI-I

(interchangeable) accepts either

Adjustments

• The on/off button, the brightness and contrast button, and the onboard menu system on the monitor allow you to make a number of adjustments.

• The physical screen adjustments and color adjustments are the two main functions provided by all monitor manufacturers

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Power Conservation

• Monitors that meet the VESA (Video Electronics Standards Association) specification for display power-management signaling (DPMS) can reduce power consumption by roughly 75 percent

• Turning off the monitor with the power switch is the most basic form of power management. It is better to leave the monitor on if you have power management!

• DPMS works with Windows Advanced Power Management (APM) or Advanced Configuration and Power Interface (ACPI) power management software

The Video Card

The Video Card

• Video RAM stores the video image

• Video processor circuitry takes the information from the video RAM and displays it on the monitor

A video card, also known as the display adapter, processes information from the CPU and sends it out to the monitor.

Video RAM

• Text video cards display only the 256 ASCII characters – For a screen with 80 characters per row and 24

rows, you would need 80 characters x 24 rows x 8 bits per character or 1,920 bytes of RAM

• Graphics video cards could turn any pixel on or off – A resolution of 320 x 200 pixels would require

64,000 bits (1 bit per pixel = on or off) or 8,000 bytes of RAM

– To add color you would need multiple bits to define the color

• To display 256 colors it takes 8 bits. For true color (16.7 million colors) you would need 24 bits per pixel. Color depth is usually represented as how many bits (color depth of 24 bits) and not the number of colors.

Color Depth Modes

• Monochrome text, color text, monochrome graphics, and color graphics are the four different types of video cards that exist. Each of these is called a video mode

• Modern video cards enable switching between modes

• IBM and then VESA defined specific, uniform video modes for video cards

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Video Cards and Standards

• Monochrome display adapter (MDA) card– First text-only video card

• Color graphics adapter (CGA) card – First-generation color display adapter that

supported colors– Four-color screen offered 320x200 resolution

Video Cards and Standards

• Enhanced graphic adapter (EGA) card – Resolutions of up to 640X360 with 16 colors in text

mode, or 640X200 and two colors in graphics mode. Late 1984

• Professional graphic adapters (PGA) card – This standard offered 640X480 resolution, 3-D

rotation, and 60-frames/second animation– Cost over $4,000 and used 3 ISA slots– Aimed at engineering community

• Video graphics array (VGA) standard – 16 colors at a resolution of 640X480 pixels (1987)– Often referred to as the minimum display

requirements on software packages

• Extended graphics array (XGA) standard – 16-bit color at a resolution of 1024X768

• Super VGA (SVGA) standard – Extensible standard - meaning that VESA adds to

the list as higher resolutions and deeper color depths develop

Video Cards and Standards Memory Requirements

• Different video modes require different amounts of RAM on the video card

• The amount of video memory required at a given resolution and color depth is determined by multiplying the resolution by the number of bytes of color depth– 24-bit color uses 24/8=3 bytes per pixel– Example: 800x600 with a 24-bit color depth

requires 800x600x3 =1,440,000 bytes of memory. If your display adapter does not have that much memory, then this mode would not be supported

Accelerated Graphics Port

• AGP is a single special port, similar to a PCI slot, which is dedicated to video– Derived from the 66 MHz, 32-bit PCI 2.1 specification– Uses its own personal data bus (PCI is limited to 32-bit

transfers at 33 MHz or bandwidth of 132 Mbps – it cannot handle some of the video demands), and supports pipelining (the steps required to process a command)

PCI Express Port

• Replacing AGP• PCI Express x16

– 2.5Gbps*16

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Graphics Processor

• The most important decision in buying a video card is the graphics processor

• Most video processors are made by– NVIDIA– ATI– Matrox– Third-party video card manufacturers use one of

these video processors on their cards

Video Memory

• The video RAM constantly updates to reflect every change that takes place on the screen

• Low cost video cards ($50-$100) use standard DRAM for video data storage

• DRAM needs to be refreshed 18.5 times per second. Also, the access/response time of DRAM is 50 nanoseconds or longer. These bottlenecks are overcome by:– Increasing the width of the bus between video RAM and

the video processor– Using specialized RAM

• Most of the graphics rendering and processing is handled on the card by the video processor rather than the CPU

Video Memory

• The three styles of RAM specifically designed for video are:– Video RAM (VRAM)

• Dual-port memory that can send and receive at the same time.• DRAM can only send or receive at a given time

– Windows RAM (WRAM)• Dual-port memory that is slightly faster than VRAM

– Synchronous graphics RAM (SGRAM)• Synchronized to the system clock• Extremely fast

• Newer, generalized RAM types such as Double Data Rate SDRAM, are often used instead of the specialized video memory above

Physical Installation Issues

• High end video cards are tall and may not fit in all cases

• High end video cards run very hot– Leave the slot next to an AGP/PCI Express card

empty to allow better air flow

Video Capture Devices

• 3D accelerator cards with TV-in ports• TV tuner cards

– PAL– NTSC

• Webcams with video input ports

Installing and Configuring Video Software

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Drivers

• As a general rule, uninstall the old video card’s drivers before installing the new ones– Choose the Settings tab

of the Display applet– Then click on the

Advanced button and choose the Adapter tab

– Click on Properties for the adapter card and then the Driver tab

• Check the manufacturer’s website for updates

Display Applet

• Found in Control panel or alt-click on the desktop and choose Properties– Settings tab

Monitor

• The monitor tab allows you to update the driver for your monitor and to set the screen refresh rate– Using a higher refresh

rate than your monitor is capable of can ruin the monitor very quickly

3-D Graphics

• 3-D graphics produce new levels of realism on the computer screen– Used for gaming and Computer Aided Design

(CAD) programs– Early 3-D graphics required proprietary computer

systems and were used almost exclusively for CAD– In 1992 a small company called id Software

launched Wolfenstein 3D and a whole new world of gaming opened up

Sprites

• Early 3-D games used sprites– Just a bitmap graphic

moved around on the screen

– Each figure had a limited number of sprites or angles of view

3-D Objects

• The second generation produced 3-D objects thru a process called rendering– Composed of a group of points or vertices– The vertices were connected with lines to produce

edges– The edges form triangles that create polygons– The last step is adding a texture (or skin)

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Transformations

• Transformations are the calculations that are necessary to produce movement by the 3-D objects– Very taxing on video cards and the PC– The process of rendering an object and perform

transformations every 1/24th of second is very demanding!

– 3-D video cards have massive amounts of RAM to store textures and fast processors to handle the transformations

– We talk to these cards using a standardized set of instructions that any 3-D game can use – OpenGL standards and DirectX

DirectX

• DirectX provides direct access to hardware as follows:– DirectDraw: for 2-D graphics– Direct3D: for 3-D graphics– DirectInput: for joysticks and game controllers– DirectSound: for waveforms– DirectMusic: for MIDI devices– DirectPlay: for multiplayer games– DirectShow: for video and presentation devices

DirectX Diagnostic Tool

• Accessories System Tools System Information Tools menu DirectX Diagnostic Tool

Dual Monitors

• Windows systems having a video card with dual outputs can be converted into a multi-monitor system with minimal effort– You may also just

install multiple video cards

• The Display Properties dialog box can be used for configuring multiple monitors

Dual-GPU Scene Rendering

• Originates from 3dfx voodoo2• 2 PCI Express video cards• Two type

– NVIDIA SLI– ATI CrossFire

• Board support

Troubleshooting Video

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Video Card Problems

• Improper drivers, poor connections, and bad monitors

• On the rare occasion where the video card is the problem, it is usually the video RAM– Fixed speckles or spots on the screen– Funny colors in Windows (provided they also appear

when booting in Safe mode)– Screen decay (usually the VRAM hasn’t been properly

inserted in the sockets)

Opening up a monitor can be deadly!

Even when the power is disconnected, certain components inside a monitor retain a substantial voltage for an extended period of time. If you accidentally short one of the components, it could actually kill you!

Warning

Suicide

• Under the suction cup is the actual high-voltage anode

• The wire leading from the suction cup goes to the flybacktransformer

• There’s a big capacitor that can hold up to 25,000 volts of charge for days, weeks, months, or even years

Lifting this suction cup will almost certainly

kill you!

Do NOT attempt todischarge a monitor

unless properly trainedand equipped!

Do NOT attempt todischarge a monitor

unless properly trainedand equipped!

Discharging a CRT

Troubleshooting Monitors

• External controls provide users with the opportunity to fine-tune the monitor’s image.– Brightness, contrast, pin cushioning, trapezoidal

adjustments– Monitors have a built-in circuit called a degaussing coil

to eliminate magnetic build up (a fuzzy looking monitor may be fixed by degaussing it)

• Low-end monitors are generally susceptible to convergence (when the three colors don’t quite meet at a single point on the screen), and can be set right by internal adjustments.– Misconvergence is most likely near the edges of the

screen

Cleaning Monitors

• Antistatic monitor wipes or antistatic cloths should be used for cleaning the monitor– Do not use window cleaners– Avoid commercial cleaning solutions on LCD

screens

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Common Monitor Problems

• Control buttons are replaceable – Check with the manufacturer

• Ghosting, streaking, fuzzy vertical edges – Check the cable connections and cable itself

• Missing color – Check cable for breaks, bent pins, and monitor

adjustments

• Loss of brightness – Normal with age, so use power management– Internal adjustments may be made

• Cracked LCD monitors – Not repairable– All other LCD problems are repairable

• Improper focus – Adjustments are inside close to the flyback transformer

• Hissing or sparking sounds and the smell of ozone – Insulation rupture requiring a qualified technician

• Big color blotches – Degauss

• Bird-like chirping sounds – Monitor power supply

• Loss of brightness but the control is all the way up – Time for a new monitor

• Single horizontal or vertical line or single white dot– Repair shop

Common CRT Monitor Problems

Do’s and Don’ts

• Do keep the screen clean

• Do keep the cables tightened

• Do use quality cabling• Do use power

management• Do dispose of

monitors properly by checking with your local waste disposal company

• Don’t block the ventilation slots

• Don’t use a refresh rate higher than recommended

• Don’t leave the monitor on all the time – even with a screen saver

• Don’t place magnetic objects like unshielded speakers close to the monitor

Video and CMOS

• Video setting for EGA/VGA has no meaning

• Init Display First– Determines which monitor to boot first in a multi-

monitor system

• Assign IRQ for VGA– Try it each way – one way works and the other

doesn’t

• VGA Palette Snoop– Not used today

• Video Shadowing Enabled– Most video cards do their own shadowing – leave

off