A DVI-I connector sends out both a digital and an an analog signal
A DVI-D cable is fully compatible with a DVI-I connector – it will only read the digital output and simply ignore the analog
Most graphics cards and motherboards feature a Digital Video Interface (DVI) connector for connecting a monitor or projector to the computer. A DVI connector is colored white (as opposed to a VGA connector, which is colored blue). For every graphics card or motherboard that has a DVI connector, the amount of pins and layout of the pins on the DVI connector varies depending on the type of DVI connector.
There are currently two types of DVI connectors, DVI-I and DVI-D.
A DVI-D connector on a graphics card or motherboard sends out a digital signal only, whereas a DVI-I connector can send both a digital signal (for digital displays, such as flat panel LCD monitors) and an analog signal (for older displays, such as a CRT monitor) using a DVI to VGA adapter. For this reason, a DVI-I connector contains more pins than a DVI-D connector.
Graphics card or motherboards which carry a DVI-I connector are therefore fully compatible with flat panel LCD monitors, which typically have DVI-D cables. The DVI-D cable will only read the digital output from the DVI-I connector and simply ignore the analog signal.