Monday, 07. October 2019 Know How
In 1987 the company IBM released the computer graphics standard Video Graphics Array (VGA). It specifies a certain combination of screen resolution, color depth and image refresh rate. At the same time also the VGA port, which has its name from the computer graphics standard, was launched as the successor of EGA.
Next to the specification for a physical interface, the VGA port also includes the classification for appropriate cables and plugs.
The VGA plug is a 15 pin Mini-Sub-D-plug with three terminal rows. What these 15 pins are for is shown in this list.
The output at the graphics card is always a socket, the input at the display can be a socket as well as a plug, anyhow the ends are always screwable. Since most of the times a socket is used, the connecting cable has to have a plug on each side. As an alternative there are also cables with a BNC plug on the display side. These have less attenuation and are shielded better than the standard VGA cable, but therefore are more expensive.
VGA transmits the data with analogue signals on 5 wires, of which three are responsible to transfer the primary colors and two for the vertical respectively horizontal synchronization. Since the signals are transferred analogously between the graphics card and the monitor, they have to be converted so that the monitor can recognize and display them.
Up until the end of the 20th century the consumer electronics and IT were strictly divided. But since the performance of devices in the consumer electronics increased immensely, the borders disappeared. The horizontal frequency of so-called “100 Hz TVs” (31.25 Hz) were very similar to the one in VGA monitors. Thus, tube TVs with VGA port were developed, but at first they were only able to display the standard resolutions of 640 x 400 and 640 x 480 pixels. Many manufacturers in the consumer electronics also use the VGA interface to implement firmware updates for TV devices.
Modern displays are nowadays dependent on digital signals, so at least in need of DVI. By using an adapter the analogue signals can the converted into digital signals, but the image quality decreases a lot by doing so. For that reason the VGA interface is almost completely dead by now.
The VGA port was initially created for a maximum resolution of 640 x 480 pixels. By using very performant graphics cards and displays, a resolution up to Full-HD, so 1920 x 1080 pixels, is possible. To display content in 4K resolution the VGA port is not enough because its transfer rate is simply too low.