Thought this was good to have around.....enjoy..and do follow the link at the bottom, more info on monitors...

(note: a little dated, but makes for a good explanation of terms and connections) 

Video

Ten years ago most video adapters had a sluggish processor, a megabyte or less of memory, and weak analog signal conversion chip. Given the memory, a user might have to choose between the number of dots on the screen (resolution) and the number of colors displayed. Limits in the analog conversion chip might force a slower refresh rate leading to a flickering screen. However, video adapters were already close to being fully adequate.

Then ten years of chip technology came along. Bumping the memory from one to four megabytes solved the color/resolution problem. Then cards had 8 megs, 16 megs, 32 megs, 64 megs, and now 128 or 256 megabytes of memory. There is certainly no plausible use for such video hardware if you just run Windows and Office. Today, the only function of a high end video adapter is to play 3D games.

This will not be true in 2007. The most visible feature of the new Microsoft Vista operating system will be its "Avalon" user interface. Microsoft will transfer much of the burden of presenting windows, menus, toolbars, and other screen elements to the processing power of current generation video adapters. Of course, if you only have an old video adapter you will continue to get the current Windows interface. However, business users in a few years will require the kind of video card that today is only useful for blasting aliens and saving the universe.

Many systems come with some video capability built into the mainboard at no cost. This video is adequate for business use on the current Windows system. Even then, there are some legitimate business reasons for buying a separate video adapter to plug into the PCI Express slot:

• Video integrated on the mainboard uses main memory. This will slow down the performance of the overall system when access to memory by the program you are running collides with access to the same memory by the video hardware. A separate video adapter card has its own memory and operates independently.
• Mainboard video typically connects to the monitor through the traditional small 15 pin analog VGA connector. The VGA connector is OK up to XGA (1024x768) resolutions and is required for a CRT monitor. However, at higher resolutions you get a sharper picture on your LCD display if you use the larger digital DVI connector. Typically you can only get DVI on an AGP video card.
• Video cards costing as little as $100 allow two monitors to be connected to the same PC. Set side by side, Windows treats them as two halves of a single desktop. You can drag applications with the mouse from one screen to the other. This expands your work surface. You can leave a database query or spreadsheet open on one screen while you compose a report or letter referencing the numbers on the other screen. Now that 20" flat LCD monitors cost $200, two display systems are a very affordable productivity aid.

However, after the cluster of basic video cards costing $100 there is a gap. The most powerful newest card cost $350 or $400. These cards are for the serious gaming enthusiast, although there might be some 3D applications in architecture. There is simply a lot more software for blasting aliens from the planet Zoron than there is for visualizing the layout of a new kitchen.

Visible Features

Resolution

Screen resolution is stated as two numbers. The first number counts the dots horizontally spaced across each line. The second number counts the number of lines from the top to the bottom of the screen. In the old days, there were five standard resolutions:

640x480 (VGA)
800x600 (SVGA)
1024x768 (XGA)
1280x1024(SXGA)
1600x1200(UXGA)

The horizontal number is always the larger of the two. There are more dots on each line than there are lines from the top to the bottom of the screen. The screen is still square. This can be explained by the fact that the "dots" are not round or square, but instead are rectangles that are taller than they are wide. The extra height of each "dot" makes up for the smaller number of them.

Screens that use these standard resolutions display a picture in approximately the standard 4:3 "aspect ratio" used for standard TV broadcast. Movies recorded on DVD and High Definition TV pictures are intended for display on a wider aspect ratio of 16:9. A small number of laptop and desktop LCD panels are designed to support this type of widescreen display.

The wider aspect ratio is designated by prepending the letter "W" in front of a standard resolution name. This means that the width has been bumped to the next larger size, but the resolution of the height has not changed. For example, XGA is 1024 wide and 768 high. The next higher standard size is SXGA which is 1280 wide and 1024 high. However, a WXGA wide aspect ratio screen has a resolution that is 1280 wide but only 768 high.

You can buy wide aspect displays with resolutions of:

1280x768 (WXGA)
1600x1024 (WSGA)
1920x1200 (WUXGA)

The wide screen resolutions have become more common with the adoption of LCD flat panel TV sets. High Definition TV has two standard resolutions of 1280x720 (just a few lines shorter than WXGA) and 1920x1080 (just a few lines shorter than WUXGA). Of course, HDTV sets will also display XGA (1024x768) but if you hook a computer up to a flat screen TV it will look better in a wide screen resolution.

A CRT monitor can switch between resolutions up to some maximum supported value. A laptop or flat panel LCD monitor generally has one native resolution that corresponds to the dots manufactured into the screen. It may support lower resolutions, but will look best at its native setting.

Brightness

An LCD display has a white backlight that shines through a screen filled with red, green, and blue bits of glass. This produces tiny dots of colored light. The active Liquid Crystal part of the LCD display is a variable polarized filter in front of each dot that controls the amount of each dot of red, green, and blue light that gets through. If all the light from all three colors gets through, the eye merges the three colors and sees a "white" light. If all the light is blocked, you see black. Otherwise, you see a generated color.

A desktop display that only has to show Excel spreadsheets and PowerPoint presentations can get along fine with a few bold color distinctions. The eye can also draw clear distinctions between different bright colors on a standard computer monitor. However, dark colors present a separate problem

One performance measurement in the specifications of every LCD panel is a measure of brightness. It is expressed in "nits" or units of brightness per square millimeter. A standard desktop LCD monitor has a brightness of 250 units. An LCD TV monitor designed to be viewed from across the room typically has a brightness of 500 units and that is the best available today. A small number of devices sold by various vendors provide intermediate values of 300, 350, 400, or 450.

A 17 inch LCD computer monitor has a resolution of 1280x1024. A 20" LCD TV, however, is often sold with a resolution of only 800x600. From across the room, you can't see high resolution. If you consider a "TV" to double as a computer monitor, check carefully its native resolution and be sure it matches a value supported by the video adapter in your PC.

Color Range

If you look even closer, each dot on the screen consists of three separate parts. One component is Red, one is Green, and one is Blue. Seen from a distance, the three components merge to form a composite which can be adjusted to any color our eye can see. Although the amount of each of the three base colors is continuous, computer equipment generally creates a range of possible brightness from 0 to 255 so that the intensity can be represented by a byte.

Ten years ago video adapters had small amounts of memory. They would save space by allocating only one or two bytes of memory for every dot on the screen. The adapter would then translate the smaller value into a full color byte. Today there are no adapters with so little memory that they cannot allocate three or four bytes per dot, even at the highest resolutions.

However, as frequently happens a new need comes along to make use of an otherwise obsolete old feature. Windows 2000, XP, and Server 2003 machines all support "remote desktop connection". When this feature is enabled, an administrator can connect to the computer over the network using the RDC client program. A window opens on the client machine and shows an image of the desktop of the remote computer. To save bandwidth, the connection can be configured to use the old one byte or two byte video modes previously used by obsolete adapters. Emulating these video modes reduces the amount of data that has to be transmitted over the network to display the desktop image.

Performance Features

Integrated or Separate Adapter?

To save money and space, smaller mainboards often come with a video adapter built in. This is attractive for corporate systems, where the only application is running office, or for Media Center systems that only have to drive the TV set.

In the past, integrated video was always crappy. However, the main suppliers of video cards now build chips for mainboards, and while integrated video is not as powerful as a separate adapter card, it can be adequate for most purposes.

If you want to play the latest video games, you want a separate video card. Otherwise, consider what you want to do and compare it with the capability of the integrated video. For example, if you intend to play Blu-ray or HD-DVD movies through the computer, then you need integrated video that will connect to your high definition monitor and you want an integrated video chip that supports decoding H.264 data.

How many Monitors?

Monitors used to be expensive. Now a 20" LCD panel can be purchased for $200, which means you can get two for $400. However, integrated mainboard video is often limited to a single monitor. Most video adapter cards support two monitors. If you want to run three monitors, you may need a second video card.

SLI or Crossfire

Video cards perform massive amounts of repetitive operations. You can buy faster video cards with faster processors, but when you reach the limit here the next step is to add a second video card and split the work between the cards. Nvidia calls this "SLI" while ATI calls it "Crossfire".

This is only interesting for video games. Unlike the previous case, where you added a second card to drive the third monitor, all the cards you use in a SLI/Crossfire configuration drive a single monitor that is running the one gaming application.

DirectX 9 or 10

The Windows programming support for games and TV applications is called DirectX. This is a programming standard that changes from year to year. Windows XP used to support DirectX 8, but today most XP users have installed the free upgrade to DirectX 9. Windows Vista comes with support for DirectX 10.

Video cards support some level of DirectX. You can always plug an old card into a new system, but it won't be able to use all the features. As this is being written (Jan 2007) there is only one graphics chip that supports DirectX 10, and all the cards that use the chip cost $400 or more. So DirectX 9 is the only cost effective solution and is generally the level of support you should look for when buying new equipment. As the year progresses, more cost effective support for DirectX 10 will become available.

Purevideo or Avivo

Video adapter hardware can also be used to offload a lot of the video stream processing when you are watching live or recorded video. This comes at several levels.

• MPEG 2 is the video compression used in DVDs, most Media Center video recording cards, and broadcast and cable digital TV (including HD broadcast programs). Some level of MPEG 2 support has been provided by all integrated mainboard and video adapter cards for the last five years (for as long as DVD movies have been widely used).
• MPEG 4 and Windows Media (WMV) are more advanced compression methods. They create smaller files (or better pictures), but they require more processing.
• H.264 is the newest compression method. It requires the most processing and provides the best compression. It may be found on some Blu-ray disks.

Each new generation of video processing chip provides hardware support for more video compression options. The Nvidia 6xxx (6000 series) of cards provided the first "Purevideo" acceleration of MPEG 2. The subsequent 7xxx cards support more video formats. The latest 8xxx cards will do better when they become more widely available.

ATI has corresponding support and a brand name called "Avivo". It is not clear exactly what that means, but you will get better hardware support for displaying video files in the 1xxx series of cards (1600, 1650, 1900, 1950) than in older cards, and newer chips will follow.

Without hardware acceleration, trying to play a Blu-ray or HD-DVD movie may run your CPU into the ground and produce unsatisfactory results.

AGP

For about a decade, video cards plugged into a special AGP video slot. The AGP slot had more data wires than PCI (64 instead of 32) and it ran at a higher clock rate (66 MHz instead of 32). Successive generations of AGP video cards transferred data 2, 4, or 8 times per clock cycle.

Each subsequent generation of AGP card ran faster, and in computer terms that means that it ran with a lower voltage level.

• AGP 1 supports 1x and 2x adapter cards with a signal level of 3.3 volts.
• AGP 2 supports 4x adapter cards with a signal level of 1.5 volts (it also supports 1x and 2x at the lower voltage, but why bother).
• AGP 3 is a new standard that will support 8x adapter cards with a signal level of 0.8 volts (and again it "supports" slower transfer, but why bother).

There are slightly different plug configurations to prevent you from accidentally plugging an AGP 1 card into a socket that only supports AGP 2 cards. Many adapter cards are configured to plug into either an AGP 1 or AGP 2 slot and to automatically adapt and run at either 3.3 V or 1.5 V.

Today there are still a few mainboards with AGP slots and a small number of cards made with AGP connectors. However, most video adapters have moved on to PCI Express.

PCI-Express

PCI Express is an entirely new bus architecture from Intel. It replaces not only the AGP slot for video, but also the PCI slots for all the other adapter cards (and the PC Card slot in your laptop). A more extensive discussion of PCI-e is provided in another article.

PCI Express transmits data over two pair of wires that provide 250 Megabytes per second in each direction. The two pair are called a "line". Additional bandwidth can be added by simply running 2, 4, 8, or 16 lines of PCI-e to the same adapter card.

Video adapter cards that use PCI-e always support the maximum 16 lines of PCI-e bandwidth. However, this is far more data transfer capability than any video card can actually use. Some mainboards provide the full 16 line slot to hold a video card, but then they only connect to the first 8-lines on the card. This is perfectly adequate for today's video cards.

If you are only running Windows and Office, you need even less bandwidth than this. For a very short time, mainboard vendors designed products where the second video card might have even fewer PCI-e lines. However, mainboard chipsets have caught up and today most mainboards can provide more PCI-e lines than anyone can meaningfully use.

External Connectors

VGA Connector

In 1987 IBM introduces a 15 pin analog video interface plug for its "VGA" display. Technically this connector is called an MD15, where M stands for "mini", D because the plug is shaped like a letter "D", and 15 because there are 15 pins in three rows. Three pairs (six pins) present a voltage level for the three colors Red, Green, and Blue.

The video adapter and display monitor negotiate a resolution and refresh rate. This information implies a particular clock rate. Each dot of each line corresponds to a particular time period. During that time, the adapter generates voltage levels for the three colors and the display generates the corresponding dot.

When IBM invented the interface, monitors had a resolution of 640x480 refreshed 60 times a second. However, the interface design would work on any resolution and refresh rate. Today it is frequently used for resolutions up to 1200x1600.

DVI Connector

The analog design of the VGA plug is a good match to the intrinsically analog operation of a CRT monitor. As long as you are using a CRT, no better interface design is possible.

However, today more people are buying flat panel LCD monitors. In the LCD each dot is an individually addressable digital element. It is more efficient and precise for the adapter to transmit digital numeric values for the color intensity of each dot.

The DVI connector is much larger than the analog VGA plug. It has lots more pins that allow digital information to be transferred between the adapter and the video monitor. The DVI plug contains both digital and analog versions of the signal, and an external converter plug can convert a DVI socket into a old VGA socket for connection to an old monitor.

It is common for high end video adapters to have both a DVI and VGA plug. LCD display panels also come with support for both DVI and VGA connectors. If you have two identical panels, you might as an experiment plug one into the DVI plug and one into the VGA plug of the same adapter. You should notice that the monitor that uses the DVI plug has a slightly sharper picture with better colors.

HDMI Connector

The smaller HDMI connector is becoming popular for consumer electronics (TV and HD DVD applications). Basically HDMI is a smaller plug version of the DVI connector, but adds a wire for digital audio. A small number of video adapter cards support HDMI today. It may become more popular, or computers may wait for the next standard to come along. Monitors may come with a cable that is HDMI on one end and DVI on the other. They will convert to real HDMI devices (Blu-ray players) or to DVI video cards.

HDTV

A high definition tube TV has the same basic design as a CRT computer monitor. A large Plasma TV hanging on a wall has a lot in common with an LCD monitor. Computer standards are so common that you can typically plug a computer into any TV that costs more than $3000.

However, there are two notable differences between TV and computer standards.

1. Standard definition TV signals (and one form of High Definition TV known as "1080i") are interlaced. The TV first receives every other line of the picture (say the odd lines). Then it goes back to the top and receives the lines that were skipped (the even ones). Any TV set can process interlaced signals, and conventional TVs can only process interlaced signals. A computer, however, generates each line one after the other. This is called progressive scan (a term that some consumers may have picked up from the description of better DVD players). A $3000 TV can process either interlaced or progressive signals, but a $300 desktop computer monitor can only handle progressive signals.
2. Every TV and computer monitor, whether CRT, LCD, Plasma, or even projector, generates the screen as a sequence of Red, Green, and Blue dots of light. The eye merges adjacent Red, Green, and Blue dots of various intensities to produce all the other colors. Computer video adapter cards work by generating values for Red, Green, and Blue directly. They then transmit these values over the analog VGA or digital DVI cable. TV, however, started as a Black-and-White system and added color later. That original design could never be removed from the standard. So even today a digital TV, cable box, or DVD player generates a black-and-white signal (Y) and then two color signals (Pr and Pb). You can generate the same picture either way. However, again a $3000 TV can receive either component TV input (Y Pr Pb), or analog computer (VGA), or digital (DVI). A computer monitor generally cannot display component TV signals.

Some computer monitors are sold with the ability to process component TV signals (the three RCA plugs colored Red, Green, and Blue that carry the Y Pr Pb signals). This allows the monitor to display HDTV from a cable set top box. Some computer video adapters contain a round connector that breaks out into the component TV signals to drive an HDTV set that doesn't support DVI. This means that in practice, everything will soon connect to everything in the video hardware area, and they will make the connection any way you want. DVI or HDMI are preferred because they will give the sharper picture. Then you can use the component connectors on your monitor for your XBOX 360.

 If you want more details on the computer-TV convergence, recording shows on you TV, and displaying HDTV on your computer, another article is available on this subject.

Copyright 1998, 2007 PCLT -- Introduction to PC Hardware -- H. Gilbert

Yeh, it is a little dated, maybe 2006, at least it makes a good glossary of terms, lol.....