1 Jan., 2008
Microsoft release 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).
Inexpensive laptop and desktop systems come with Video adapter capability built into the mainboard. Until recently any integrated video was notably less powerful than a separate video card, but Vista has forced Intel, Nvidia, and ATI to significantly increase the power of their integrated video processors.
You want a separate video card if you play 3D computer games. There may still be a small advantage of a separate video card when playing High Definition Blu-Ray movies. Other than that, however, integrated video may be perfectly capable, less expensive, and use less power and generate less heat than a separate card.
Whether you use integrated video or a separate card, make sure you get a digital connector. DVI is a start, but you want the ability to connect to HDMI. Most modern systems can turn DVI into HDMI or HDMI into DVI so either connector will work on the mainboard or card. There is a new video connector standard that should begin to show up in a few years.
If you have a really powerful monitor screen with a resolution like 2560x1600 you need "dual link" DVI, and that may require a modern adapter card.
At one time there were a set of standard computer screen resolutions. Then customers started to ask for wider screens that could display HDTV and DVD movies properly in full screen mode. Then HDTV added two specialized resolutions that really came from TV standards.
Today modern video drivers can handle all sorts of resolutions and screen sizes. There is a plug-and-play protocol where the monitor tells the computer what screen resolutions it supports and prefers and the video driver software selects the best choice.
The defaults work correctly much of the time. The system chooses the native resolution of the screen, the Windows interface fills the entire monitor, and everything appears sharp and bright. Unfortunately, the world of TVs includes something called "overscan" where TV sets normally clip off some extra picture from the left, right, top, and bottom of the screen. As computer monitors include some TV function, and flat TV sets are used as computer monitors, there is room for two types of error. One occurs when the screen shrinks the Windows desktop, which no longer fills the entire screen but has a black border around it on all sizes. The other occurs when the desktop expands and the left, right, top, and bottom edges (including the task bar and Start button) are pushed off the screen.
The solution is sometimes as simple as choosing a different refresh rate. Changing the default 60Hz to 50Hz or 70Hz may correct the problem and display the correct desktop. If you are using a TV resolution (720p or 1080p) then updating to the latest release of the ATI or Nvidia driver may give you a control to correct an overscan problem.
Know what the native resolution of your monitor is. Best results will be produced when that is the resolution that the video card decides to use.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
This is an "analog" connection, because the brightness of the Red, Green, and Blue lights for each dot on the screen are determined by the voltage level of the three pairs of wires when that dot is being generated.
The resolution determines the number of lines on the screen and the number of dots per line. Then there is a refresh rate, the number of times that the screen is redrawn each second. These numbers establish the amount of time to draw the entire screen, then to draw a single line, and then to draw a single 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.
The computer operating system or program tells the video card what to display by assigning a number to the Red, Green, and Blue value of each dot, line, or box. If the adapter card is connected to a monitor with a VGA connector, then it has to turn these numbers into voltage levels for the three pairs of wire, and the monitor has to sample the voltage level to try and recover the original color value.
As old CRT monitors have been replaced by flat panel monitors with internal computer chips, it has become much more efficient to simply transfer the information digitally, as numbers instead of voltage levels. The DVI cable represents a compromise. It has a digital data bus over which the adapter card can transfer numeric data just as the USB, eSATA, or FireWire cables transfer digital data. However, because the world of video has not yet adapted entirely to digital display, it also has connectors for the old analog Red, Green, and Blue voltage levels.
You can plug a digital display into the DVI plug. If you have a monitor that requires the old VGA connector, there are adapter plugs that connect to the DVI plug and produce the old MD15 VGA connector. At power up the video adapter card determines if a monitor is connected to the digital or analog pins and generates one or the other.
Since most monitors have both analog and DVI connectors, and DVI video cards can be converted to use the old analog plug, you can run the same computer and monitor on both digital and analog video switching back and forth to compare the pictures. Generally the digital picture will be a little sharper with better colors.
The DVI plug has room for two sets of pins, but typically only one set of pins is used. When both sets of pins are available, and the DVI cable has the extra set of wires, then this is a Dual Link DVI plug. This can be required for the very highest resolution supported by 30" computer monitors.
The analog connection to a High Definition TV set is typically through a "component" cable that has three RCA connectors colored red, green, and blue. This is not the way you would hook up a computer to a desktop monitor to run Word or Excel, but when you add a computer on the shelf with your stereo equipment and control it with a remote control instead of a keyboard, then it is common to use a video adapter card that supports component TV output.
HDMI is a digital connection like DVI. There are plugs and cables to convert HDMI to DVI. HDMI is smaller than DVI, because it has no pins for analog compatibility.
An HDMI physical plug is often (but not always) associated with the HDCP protocol. HDCP is an encrypted data transfer protocol for video just as SSL encrypts data on the Web. The movie studios require licensed vendors to transmit digital High Definition movie content only over HDCP encrypted connections, to prevent any device from making copies of the digital data stream.
Blu-Ray players require HDCP when you use an HDMI connection. The Sony Playstation 3 will connect digitally only to a monitor that does HDCP over HDMI.
The current generation of Nvidia and ATI video cards support HDCP over DVI or HDMI connectors. However, this flexibility produces an incompatibility. Video adapter cards may be able to negotiate HDCP encryption with panels sold as computer monitors that also support HDCP. However, a big HD TV set may only be able to use the single mode HDCP over HDMI generated by the Playstation 3 or a standalone Blu-Ray player.
If you cannot connect your preferred monitor to your computer with HDCP, then playing Blu-Ray or HD DVD disks from the computer to the monitor will require using an analog connection (old VGA plug that all video adapters support or component TV cable that some support).
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