What is VGA ? How does it work ?
VGA (Video Graphics Array) is a basic standard for color resolution in computer monitors that, today, represents the lowest common denominator for compatibility. For example, when a computer boots into the Microsoft™ Windows™ operating system, the opening splash screen or Windows logo is presented in VGA mode using a palette of 32 colors and a resolution of 640 x 480. Once the system is fully loaded, the video card’s device driver takes over at a higher resolution.
Although it would be a few years before IBM released another formal video standard, other video card manufacturers quickly began producing cards that could support higher resolutions and color depths than IBM’s VGA standard. These various capabilities were informally called “Super VGA” modes, which over time came to mean “anything better than 640 x 480 at 16 colors.” (Eventually, the Video Electronics Standards Association (VESA) helped consolidate these disparate standards and produced a “Super VGA” standard programming interface that included, among other things, a defined 800 x 600 at 16 colors resolution.)
IBM’s next standard of note was called “XGA”, which offered a maximum resolution of 1024 x 768 with 256 colors. It could also produce 640 x 480 resolutions with what was at the time a stunning 65,536 colors.
Since that time, continued improvements in technology have pushed resolutions higher and higher, with increasing color depths. Along with these improvements has come a slew of acronyms to define them, which are shown in the table below. In practice, most of these acronyms are rarely used, and the terms “VGA” and “Super VGA” (or “SVGA”) are used instead.
So, why does a cable company worry about different video standards ? Well, as one would expect, higher resolutions and color depths mean more data going through a cable. In fact, the original VGA cables used when IBM developed the VGA standard are no longer appropriate for modern resolutions. Most of us in the cable industry are careful to differentiate between the informal terms “VGA cable” and “SVGA cable,” which have physically different constructions.
A traditional VGA cable was fairly simple. It consisted of 14 or 15 28 AWG (28 gauge) wires in a jacket, with 15 pin connectors on either end. These cables, still in use today on older equipment, are suitable for the relatively low resolutions of the original VGA standard.
However, it quickly became clear, as resolutions were increased, that a new cable design was going to be necessary. Recognizing that the most critical data flowing through the cable is the red, green, and blue color data, super VGA cables (which are sometimes marketed as “XGA cables”) were designed to minimize any interference from compromising the signal along those lines.
Rather than just using a pair of wires (one for signal, one for ground) for each color channel – as had previously been done with traditional VGA cables – the newer SVGA cables were designed with three miniature coaxial wires inside the main cable. (Coax cable is a broad term referring to any cable that has a center pin delivering data, surrounded by insulating material and one or more shields that provide grounding and mitigate external interference.) Well-constructed SVGA cables are cable of carrying high resolutions (up to 2048 x 1536) at distances up to 100 feet without external amplification.
When purchasing these cables, you should always take care to purchase Super VGA cables, not standard VGA cables, unless you know for absolute certainty that you will only ever run a low-resolution device. Even then, it is probably advisable to stick with Super VGA cables, to ensure that the cable you purchase today will continue to work into the future.
One Response to “What is VGA ? How does it work ?”
By bluetooth headphones on Sep 16, 2009 | Reply
This is a complete information vga and how it works. I am using vga cable in my HP 1000 but i don’t know the background process of that so thanks for clearing my concept on vga.