Video

Microsoft released Windows 3.0 in the first quarter of 1990. It was an instant success, but it did use a lot of CPU to move the cursor around on the screen, to move and resize windows, and scroll text up and down. Soon Windows was shipping on every computer, and hardware vendors had a great incentive to optimize its performance. By 1995 every video hardware vendor had added hardware that optimized the cursor, scrolling, moving, and the rest of the 2 Dimensional Windows/Office interface.

For the next 10 years, the big problems in Windows video came from 3D games and multimedia (displaying DVD or TV pictures in a window on the screen). Rather than extending the operating system interface that handled the mouse, menus, titles, status, buttons, and scroll bars of standard text windows, Microsoft create an entirely separate program interface for games and multimedia called DirectX.

Of course, there is some overlap. An application program that displays TV or a DVD movie on the screen uses the old interface to write the top title bar, menu, and any button controls that stop, fast forward, or reverse. It only uses DirectX to run the actual movie in the big middle window. For ten years video card vendors pretty much ignored the Window interface and concentrated on DirectX, games, and multimedia. This meant that the Windows user interface was frozen to a time when video cards had 2-4 megabytes of memory.

This changes with Windows Vista. The old Windows interface now makes use of the same 3D capability on the video card that games have used for the last decade. This allows some of the nifty 3D displays and rotations that Vista makes possible (though almost nothing really uses).

Integrated

All laptop computers and some desktop computers (with MATX mainboards) have integrated video built into the mainboard. Until 2008, integrated video meant crummy video with limited performance. Today Intel, Nvidia, and AMD/ATI all offer integrated video chips based on current generation GPUs with a reasonable amount of dedicated video memory. This will not provide the kind of performance that gamers want from a 3D system, but it is good enough for every other purpose. It will also reduce electrical power use because integrated video is more efficient than a separate card.

If you look at systems with integrated video, look for DirectX 10 support (rather than 9). Also look for hardware support in the video chip for H.264 and VC1 (the formats used on HD Blu-Ray disk files). Even if you do not intend to use the system for video, support for HD in the hardware is an easy indicator that you are getting a modern system and not one of the older chips that only does DVD MPEG 2.

Connection

The integrated video or separate adapter card connect to the monitor over an old analog VGA connector or a new digital DVI or HDMI connector. The digital connectors produce the best picture.

DVI and HDMI are basically the same connection with different plugs. You can buy a cable that is DVI on one end and HDMI on the other to convert between them. DVI is mostly a computer standard but is used on a few consumer electronic products, while HDMI is mostly a consumer electronic standard that exists on some computers to connect them to HD TV sets and to allow the playback of Blu-Ray movies on a big screen TV (if your computer has a Blu-Ray disk reader).  

There is a new standard called DisplayPort, but it exists on about three products currently available for sale. It will be important in the future, but whether that means 2009 or 2010 nobody can say at the moment.

If you have lots of money and buy one of those 30 inch Dell, HP, or Samsung monitors with the 4 or 6 million pixel resolutions, you may need a "dual link" DVI connection. That is available on some video adapter cards (check the specs).

Resolution

The screen has a certain number of lines. Each line has a certain number of dots. In 1987 a screen with 768 lines of 1024 dots was about as much as you could hope for. Today there is no practical limit on screen size or resolution, although it helps to win the lottery before you go shopping.

Screens used to be nearly square (actually 4x3 in ratio). Then DVD movies came along and a more cinematic "wide aspect" screen image with a ratio of (16x9). This produced a second set of resolutions for wide screen displays. So eventually the video card vendors stopped supporting only specific resolutions. Today the monitor at start up time tells the video card what resolutions it supports, and the card tells the operating system, and Windows lets you choose.

However, this does not work for devices that really are just TV sets. They may connect to a DVI or HDMI plug on the computer, but the rules of TV are different from the rules for computer monitors. Mostly, there is the problem of "overscan". For sixty years, the TV stations broadcast a slightly larger picture than the TV sets actually displayed. This was required for picture tube TVs where the picture on the left and right ends of the tube were slightly distorted by the way picture tubes were manufactured. The old sets simply covered over the left and right ends of the tube so you didn't see the distortion. This difference between what was broadcast and what you saw is called "overscan".

When you hook your computer up to something that really, really wants to be a TV, you may find that the sides, top, and bottom of the desktop have been "pushed" off the edges of the display. You have to install the Nvidia or ATI control program and then adjust the overscan to make sure you see the entire desktop.

A 20" computer monitor on your desk typically has a higher resolution than a 50" TV set hanging on the wall across the room. The highest TV resolution is 1920x1080, and your eye doesn't see finer detail from a distance. Less expensive TV sets have an even lower resolution of 1280x720.

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 nits. An LCD TV monitor designed to be viewed from across the room typically has a brightness of 500 nits.

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.

HDTV

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, 2008 PCLT -- Introduction to PC Hardware -- H. Gilbert