The information processed by the graphics card is ultimately output to the display. The output interface of the graphics card is a bridge between the computer and the display. It is responsible for outputting corresponding image signals to the display. Because of its design and manufacturing reasons, CRT monitors can only accept analog signal input. This requires the graphics card to output analog signals.
The VGA interface is the interface for outputting analog signals on the graphics card, and the VGA (Video Graphics Array) interface, also called the D-Sub interface. Although liquid crystal displays can directly receive digital signals, many low-end products use VGA interfaces in order to match the VGA interface cards. The VGA interface is a D-type interface with a total of 15 pins empty, divided into three rows of five in each row.
The VGA cable originally contains 14 wires and 15 holes (the 9th pin can be used as the USB power supply line, and it can also be used as a blind pin: empty foot), 5 of which transmit the VGA main signal, and 4 main data signal lines. CLK line DAT line ground and so on. However, from the perspective of transmitting VGA video, many wire-line manufacturers’ engineers think that the other four have no effect and will be omitted.
So there is a similar argument that there is no television data feedback. In fact, it is cutting corners! This is the so-called VGA cable 3+2, 3+4, 3+6, 3+9 origins, all referring to the number of internal lines!