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【标准】计算机视频显示标准介绍(英文) - Super VGA (SVGA)

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【标准】计算机视频显示标准介绍(英文)
MDA
HGC
CGA
EGA
PGC
8514
VGA
MCGA
SVGA
XGA
SXGA
QXGA
HXGA
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Super VGA (SVGA)

Super VGA was first defined in 1989 by the Video Electronics Standards Association (VESA); an association dedicated to providing open standards instead of the closed standards from a single company (IBM). While initially defined as 800x600 with 16 colors, SVGA evolved to 1024x768 with 256 colors and even higher resolutions and colors as time went on.

As a result SVGA is more of an umbrella than a fixed standard. Indeed, most any graphics system released between the early 1990s and early 2000s (a decade!) has generally been called SVGA. And, it was up to the user to determine from the specifications if the graphics system supported their needs.

The VESA SVGA standard was also called the VESA BIOS Extension (VBE). VBE could be implemented in either hardware or software. Often you would find a version of the VBE in a graphic card's hardware BIOS with extensions in software drivers.

How could a standard be so fractured? With the introduction of VGA, the video interface between the adapter and the monitor changed to analog from digital. An analog system can support what is effectively an infinite number of colors. Therefore, color depth largely became a function of how the video adapter was constructed and not the monitor. Therefore, for a set of different monitors there could be thousands of different video adapters that could connect to the monitors and drive them accordingly. Of course, the monitors had to be able to handle the various refresh frequencies and some had to be larger to support the increasing number of pixels but it was easier to produce a few large multi-frequency monitors than it was to produce the graphics computing power necessary to drive them.

Thus, while SVGA is an accepted term, it has no specific meaning except to indicate a display capability generally somewhere between 800x600 pixels and 1024x768 pixels at color depths ranging from 256 colors (8-bits) to 65,536 colors (16-bits). But, even those values overlap the various XGA standards...