Through the course of PC development, there have been a variety of different and competing video display standards developed. Since the Video Electronics Standards Association (VESA) came out with an agreed-on SVGA spec, there has not been much volatility in this area. This is good news for consumers because you don’t have to worry about getting hardware to support certain video standards. But, before SVGA, there were several, and some of them are outlined below.
MDA (Hercules)
Monochrome Display Adapter, or MDA, came out in 1981 and is the oldest display standard for the PC. This was the original display adapter on the IBM PC. Technically, it was a character-mapped system, meaning it was capable only of 256 special characters in set positions on the screen. This was text-only and no color. Text was available in 80 columns and 25 rows, and each character was of a set size. It is not capable of pixel-by-pixel control, therefore no graphics can be shown with it. It was ideal for simple DOS based applications with no graphics, like word processing. As a plus, IBM included an integrated printer port, thereby saving another slot.
CGA
A few months after the release of the MDA, the CGA adapter came out. It worked with an RGB monitor and worked off the bit-mapped method, meaning it was capable of the pixel-by-pixel control needed for graphics. It could also do 16 colors, 4 at a time, on a 320 x 200 display. The pixels were quite large and the resolution was bad, but it could do graphics. CGA offered a high-resolution mode of 640 x 200, but then it could only do two colors. Besides its limitations, this card remained very common for quite a while. It had a couple annoyances, which were flicker and snow. By snow, I mean one would sometimes get random dots on the screen.
EGA
After a few years, the llimitations of CGA grew quite apparent to users. The Enhanced Graphics Adapter was next in the line. It stands between the CGA and the good old VGA cards. It was introduced in 1984 and was continued until 1987, when the first IBM PS/2 systems were set to market. It was a nice graphics card at the time, but it couldn’t deliver the vast array of colors we all like today, so it is thus forgotten. It could produce 64 colors, but displayed only 16 of them at one time when used with an EGA monitor. It had a high-resolution mode and a monochrome mode, and was compatible with all previous monitors, including CGA and monochrome.
One new feature on the EGA adapter was the memory expansion board. The EGA card came standard with only 64K of memory. With a memory expansion card, you got an extra 64K, for a total of 128K. Then, with the addition of a special IBM memory module kit, you could add another 128K, for a total of 256K of graphics memory. One good thing, though, was that most aftermarket EGA cards came equipped with the full 256K of memory.
PGA
In 1984, IBM introduced the Professional Graphics Array, or PGA. The name gives away its intended audience. This system, priced at almost $5,000, was intended for serious scientific or engineering applications. With a built on 8088 processor, it could perform 3D manipulation and animation at up to 60 frames per second at a full 256 colors at 640×480 resolution. Besides the price, this system took up a total of three motherboard slots. Obviously, the cost precluded this system from ever taking on to the general public, and was later dropped. It would be quite a feat to see one of these things today.
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