DVI cables are used with DVI-enabled graphics cards to utilize the Digital Visual Interface, (sometimes called Digital Video Interface), in order to maximize the benefit of flat panel digital displays.
The traditional Video Graphics Array (VGA) interface was designed for use with analog CRT (cathode ray tube) monitors. It converts digital signals received from the graphics card into analog signals which it sends to the monitor. This conversion to analog creates minute distortions in the integrity of the signal. While necessary for CRT monitors, flat panel displays are themselves digital. With a DVI interface on the video or graphics card, pure digital output can be achieved using DVI cables, resulting in a sharper picture.
There are several types of DVI cables or connectors. Some transfer both analog and digital signals to accommodate intermixed components, as this digital interface acted as a bridge between the market transition from VGA and CRT monitors to digital monitors. The main types of DVI cables are:
DVI-D (Digital, for use with digital displays): These cables link DVI-graphics cards to digital displays. They transfer digital-to-digital signals, eliminate analog conversion and cannot accommodate CRT displays.
DVI-A (Analog, for use with analog displays): These DVI cables run from the DVI graphics card to an analog CRT display, converting digital-to-analog. Although some purity is lost in the conversion from digital to analog, using a DVI card and DVI-A cable with a CRT monitor delivers superior performance to using a VGA interface.
DVI-I (Integrated, for use with either display): These cables work as digital-to-digital or analog-to-analog, hence their designation as "integrated." They do not convert digital-to-analog or analog-to-digital. These DVI cables can be used to connect a DVI graphics card to a digital display, or a DVI card's VGA interface to an analog display.
DVI-DL (Dual Link): DVI cables can be single link, or dual link. Dual link cables have the ability to provide greater speed, greater signal quality and extremely high resolutions by utilizing an additional "pipeline" when the first line has been maximized. This is especially relevant in very large-screen displays requiring high resolutions of over 2.3 million pixels. By comparison, most 17-inch to 19-inch digital displays have a native resolution of about 1.3 million pixels.
When purchasing DVI cables, check with a knowledgeable salesperson to make sure the cables you are buying are right for your components. It might also be of interest to note that the DVI standard has been superseded by the Unified Display Interface (UDI) and DisplayPort standards.