VGA Adapter
VGA (Video Graphics Array) was the display hardware used with IBM PS/2 computers beginning in 1987. Instead of being called a VGA adapter, it was referred to as an array because it was implemented as a single ASIC chip. Today the term denotes any display adapter or graphics card that can handle VGA resolutions.
Other Uses of the Term
While VGA technically refers to the hardware, computer users also use the term to refer to the 640×480 resolution. It also refers to the 15-pin connector or the analog PC display.
Officially the display was replaced by IBM’s XGA. However the phrase “Super VGA” is used by both manufacturers and computer users for resolutions that go beyond what VGA is capable of.
VGA Adapter Technical Specifications
The original hardware came with 64 KB, 128 KB or 256 KB of video RAM. The color modes consist of the 16 color and 256 color modes. It also has a master clock of 25.175 MHz or 28.322 MHz. The number of horizontal pixels is limited to 800, and the number of maximum lines is 600.
The refresh rates are up to 70 Hz. Some cards also have support for vertical blanks. There are 16 colors in planar mode and 256 colors in packed pixel mode. There is also support for smooth scrolling, Raster Ops and split screen.
The VGA adapter has support for All Points Addressable graphics modes. The typical graphics modes when the adapter came out were 640×480 in 16 colors, 320×200 in 16 colors, 640×350 in 16 colors and 320×200 with 256 colors. The adapter was also designed to imitate the modes of the display adapters that preceded it, including EGA and CGA.
VGA Connectors
The connector has three rows and 15 pins. It is also called a D-sub 15, mini sub D15 or RGB connector. Currently there are four versions: the one with the VGA15 connector, the DDC2 pinouts, the Mini VGA (for use on laptops) and the DE-9.
The VGA adapter with 15 pins is standard in most graphics cards and computer monitors. HDTVs that support VGA also use the 15 pin connector. It is called High Density 15, HD-15 or DE-15. These connectors are used for carrying DDC2 (display data channel) digital clock, RGBHV (red/green/blue – horizontal sync – vertical sync) and other data.
Connector Layout
A 15-pin VESA DDC2/E-DDC connector is set up in the following way: pins 1, 2 and 3 are for red, green and blue video; pin 4 is reserved and pin 5 ground (HSync). Pins 6, 7 and 8 are red, green and blue returns.
Pin 9 is +5V DC and pin 10 ground (VSync, DDC). Pin 11 is reserved and pin 12 is PC data. Pin 13 is for horizontal sync and pin 14 for vertical sync. Pin 15 is the PC clock.
In spite of various innovations in technology, VGA adapters remain widely utilized. By understanding how the term is used in the industry, you’ll avoid mistakes when you buy a video card or use it to connect to a TV.
