For each different type of graphics adapter card that can be used with Windows NT, there must be both a display driver and a corresponding video miniport driver. The miniport driver is specific to the adapter (or a family of adapters), but a display driver can be specific to a class of adapters with a common drawing interface. This is because the display driver draws and the miniport driver performs operations such as mode sets and provides information about the hardware to the driver.
More than one display driver can work with a given miniport driver. For example, the 16- and 256-color SVGA display drivers can use the same miniport driver. A display driver can also work with more than one miniport driver if the adapter types provide the same drawing interface. One example is the VGA display driver, which can be used with either the VGA miniport driver or the ET4000.
There are four general types of video hardware: