[ The PC Guide | Systems and Components Reference Guide | Video Cards | Video System Interfaces ]

Feature Connectors

Many video cards contain what is called a feature connector. This is an additional connector that is used to connect the video card to other video devices such as 3D accelerators, MPEG decoders and video capture cards. The reason that these connectors are used is that they permit the direct transfer of video information from these devices to the video card, without having to use the main system bus. Even high-performance local buses can get bogged down when trying to deal with the enormous amount of information that, for example, a full-motion video stream represents.

There are different feature connector standards on the market today:

• Video Feature Connector (VFC): This original feature connector was part of the original VGA specification. Standard VFCs are 8-bit ports using a 26-pin connector, and are limited to the lower resolutions and color depths of standard VGA. This is now an obsolete standard and is not used by higher-end cards.
• VESA Advanced Feature Connector (VAFC): Developed by VESA as an extension to VFC, VAFC widens the port from 8 bits to 16 or 32, and provides improved signaling for more reliability. The VAFC provides a high-bandwidth conduit to the video card and uses an 80-pin connector.
• VESA Media Channel (VMC): This is a more advanced standard that in essence, defines another bus within the PC for interfacing together multiple video streams. This system allows several units to be integrated together in a sort of "back alley" bus, and uses a 68-pin connector.

Next: Video Card "Bit Width" vs. System Bus Width

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