Video Graphics Array (VGA) is a video display controller and accompanying de facto graphics standard, first introduced with the IBM PS/2 line of computers in 1987, which became ubiquitous in the IBM PC compatible industry within three years. The term can now refer to the computer display standard, the 15-pin D-subminiature VGA connector, or the 640 × 480 resolution characteristic of the VGA hardware. VGA was the last IBM graphics standard to which the majority of IBM PC compatible computer manufacturers conformed, making it the lowest common denominator that virtually all post-1990 PC graphics hardware can be expected to implement. VGA was adapted into many extended forms by third parties, collectively known as Super VGA, then gave way to custom graphics processing units which, in addition to their proprietary interfaces and capabilities, continue to implement common VGA graphics modes and interfaces to the present day. The VGA analog interface standard has been extended to support resolutions of up to 2048 × 1536 for general usage, with specialized applications improving it further still.
Hardware design The color palette random-access memory (RAM) and its corresponding digital-to-analog converter (DAC) were integrated into one chip (the RAMDAC) and the cathode-ray tube controller (CRTC) was integrated into a main VGA chip, which eliminated several other chips in previous graphics adapters, so VGA only additionally required external video RAM and timing crystals. This small part count allowed IBM to include VGA directly on the PS/2 motherboard, in contrast to prior IBM PC models – PC, PC/XT, and PC AT – which required a separate display adapter installed in a slot in order to connect a monitor. The term array rather than adapter in the name denoted that it was not a completely independent expansion device, but a single component that could be integrated into a system. Unlike the graphics adapters that preceded it (MDA, CGA, EGA and many third-party options), there was initially no discrete VGA card released by IBM. The first commercial implementation of VGA was a built-in component of the IBM PS/2, in which it was accompanied by 256 KiB of video RAM, and a new DE-15 connector replacing the DE-9 used by previous graphics adapters. IBM later released the standalone IBM PS/2 Display Adapter, which utilized the VGA but could be added to machines that did not have it built in. On some machines and cables, pin 9 was missing. Pin 9's purpose is to power an EEPROM chip in the monitor, which tells the graphics card the capabilities on the monitor. Systems or cables missing this are likely using an older version of VGA.
Capabilities
The VGA supports all graphics modes supported by the MDA, CGA and EGA cards, as well as multiple new modes.
Standard graphics modes 320 × 200 in 4 or 16 colors (CGA/EGA compatibility) 320 × 200 in 256 colors (Mode 13h) 640 × 200 and 640 × 350 in 16 colors or monochrome (CGA/EGA compatibility) 640 × 480 in 16 colors or monochrome The 640 × 480 16-color and 320 × 200 256-color modes had fully redefinable palettes, with each entry selected from an 18-bit (262,144-color) gamut. The other modes defaulted to standard EGA or CGA-compatible palettes and instructions, but still permitted remapping of the palette with VGA-specific commands.
640 × 480 graphics mode The 640 × 480 resolution (at 256 colors rather than 16) was originally used by IBM in PGC graphics (which VGA offers no backward compatibility for) but did not see wide adoption until VGA was introduced. As the VGA began to be cloned in great quantities by manufacturers who added ever-increasing capabilities, its 640 × 480, 16-color mode became the de facto lowest common denominator of graphics cards. By the mid 1990s, a 640 × 480×16 graphics mode using the VGA memory and register specifications was expected by operating systems such as Windows 95 and OS/2 Warp 3.0, which provided no support for lower resolutions or bit depths, or support for other memory or register layouts without additional drivers. Well into the 2000s, even after the VESA standard for graphics cards became commonplace, the "VGA" graphics mode remained a compatibility option for PC operating systems.
Other graphics modes Nonstandard display modes can be implemented, with horizontal resolutions of:
512 to 800 pixels wide, in 16 colors 256 to 400 pixels wide, in 256 colors And heights of:
200, or 350 to 410 lines (including 400-line) at 70 Hz refresh rate, or 224 to 256, or 448 to 512 lines (including 240 or 480-line) at 60 Hz refresh rate 512 to 600 lines at reduced vertical refresh rates (down to 50 Hz, and including e.g. 528, 544, 552, 560, 576-line), depending on individual monitor compatibility. For example, high resolution modes with square pixels are available at 768 × 576 or 704 × 528 in 16 colors, or medium-low resolution at 320 × 240 with 256 colors. Alternatively, extended resolution is available with "fat" pixels and 256 colors using, e.g., 400 × 600 (50 Hz) or 360 × 480 (60 Hz), and "thin" pixels, 16 colors and the 70 Hz refresh rate with e.g. 736 × 410 mode. "Narrow" modes such as 256 × 224 tend to preserve the same pixel ratio as in e.g. 320 × 240 mode unless the monitor is adjusted to stretch the image out to fill the screen, as they are derived simply by masking down the wider mode instead of altering pixel or line timings, but can be useful for reducing memory requirements and pixel addressing calculations for arcade game conversions or console emulators. The PC version of Pinball Fantasies has the option to use non-standard, "high res" modes, such as 640 × 350, allowing it to display a larger portion of the pinball table on screen. The game Scorched Earth uses a default resolution of 360 × 480, with many other nonstandard resolutions available.
Standard text modes
VGA also implements several text modes:
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