Monitor Cabling Guide / Video Display Standards

Since there are many different ways to specify a video card's capabilities, and so many potential resolutions, colour modes, etc., video standards were established in the early years of the PC, primarily by IBM. The intention of these video standards is to define agreed upon resolutions, colours, refresh modes, etc., to make it easier for the manufacturers of PCs, monitors, and software to ensure that their products work together.

In recent years, IBM's fall from dominance has left the video industry without any clear leader to set standards. This, combined with the desire by various manufacturers to develop newer and faster cards, has left the current market with a plethora of different standards. The Video Electronics Standards Association (VESA) was formed to define new standards and has had some success in creating widely-accepted new standards.

SUPER VGA (SVGA) AND OTHER STANDARDS BEYOND VGA

VGA was the last well-defined and universally accepted standard for video. After IBM faded from leading the PC world many companies came into the market and created new cards with more resolution and colour depths than standard VGA (but almost always, backwards compatible with VGA).

Most video cards (and monitors for that matter) today advertise themselves as being Super VGA (SVGA). What does a card saying it is SVGA really mean? Unfortunately, it doesn't mean much of anything. SVGA refers collectively to any and all of a host of resolutions, colour modes and poorly-accepted pseudo-standards that have been created to expand on the capabilities of VGA. Therefore, knowing that a card that supports "Super VGA" really tells you nothing at all. In the current world of multiple video standards you have to find out specifically what resolutions, colour depths and refresh rates each card supports. You must also make sure that the monitor you are using supports the modes your video card produces; here too "Super VGA compatible" on the monitor doesn't help you.

To make matters more confusing, another term is sometimes used: Ultra VGA or UVGA. Like SVGA, this term also means nothing. Some people like to refer to VGA as 640x480 resolution, SVGA as 800x600, and UVGA as 1024x768. This is overly simplistic however, and really is not something that you can rely upon.

VESA SUPER VGA STANDARDS

In an attempt to bring some order to the chaos of competing and incompatible Super VGA standards on the market, the Video Electronics Standards Association (VESA) has worked to establish new video interface standards. The intention of these standards is to once again provide a standardised application program interface between video hardware and application software. This would allow software developers to write their code to work with a single standard video model instead of having to write custom code to support the many different cards in use in the market today.

Originally ignored by many vendors, VESA support is now becoming generally accepted as beneficial, and something that buyers look for when shopping for a video card. This is in part due to the growing number of programs (especially games) that require VESA SVGA compatibility in order to function at peak performance.

The VESA SVGA standard is called the VESA BIOS Extension, sometimes abbreviated as VBE. There are actually more than one now, as more than one version of the standard exists. What's interesting about VBE is that it can be implemented in either hardware or software. Some video cards support a particular VBE standard in hardware. Those that do not can use a small memory-resident program--which is sometimes called a "VESA driver" even though it technically isn't a driver--that will provide VESA support for many cards that don't support VBE natively. This flexibility has helped encourage the widespread adoption of the standard because even proprietary hardware can be made to work with standard software, mostly transparently.

SIZE AND RESOLUTION

The monitor size measurement refers to the diagonal size of the monitor's CRT (Cathode Ray Tube), not to the measurement of what you can actually see on the screen. That is because the plastic rim that holds the monitor together masks a small portion of the CRT. The portion of the screen you can see is the viewable image size and is an inch or two smaller than the monitor size measurement.

The most popular CRT sizes are 14", 15", 17", 19", 21".

The Monitor resolution is a number of picture elements or pixels that are used to produce an image on the display. The pixel resolution of the image is specified by means of:

(a) the number of pixels in each horizontal row, which is the same as how many vertical lines it is possible to see (if the horizontal resolution is 800 it is possible to see 400 white/black lines [1pixel/1pixel])

(b) the number of pixels in each vertical column on the screen, which is the same as how many horizontal lines it is possible to see (if the vertical resolution is 600 it is possible to see 300 white/black lines) [1pixel/1pixel]).

The nominally used formula is H x V. Examples:

640 x 480 -> 307 200 addressable pixels.

800 x 600 -> 480 000 addressable pixels.

1600 x 1200 -> 1 920 000 addressable pixels.

The most popular resolutions are:

640x480, 800x600, 832x624, 1024x768, 1152x870, 1280x1024, and 1600x1200.

The smallest PC monitors measure 14 inches -- an adequate size for viewing applications at 640x480 or 800x600. For comfortable viewing of 800x600 resolution, 15" size is better. To see multiple applications on the screen at the same time, or to see the quality in a 1,024x768-pixel image, a 17-inch screen will be a better choice. With a 20- or 21-inch monitor, you can comfortably view 1,280x1,024 resolution, the maximum supported by the Super VGA standard. These are more expensive and are used primarily for specialised applications that require a lot of screen space. Monitors measuring in the 40-inch range and costing thousands of pounds are available from several manufacturers, but again, these are for computer-aided design, pre-press and other high-end uses.

An important point is that the computer's video system should support the same maximum resolution as the monitor used with it. If the monitor can go up to 1,280x1,024 but the video system can only handle 800x600, it will never be possible to take advantage of the monitor's 1,280x1,024 resolution.