Mini-DIN connectors are 9.5 mm in diameter and come in seven patterns, with the number of pins from three to nine. Each pattern is keyed in such a way that a plug with one pattern cannot be mated with any socket of another pattern. An important aspect of why each of these 7 mini-DIN connectors are official standards is because they are each drastically different from the other, with no simultaneously and directly overlapping similarities in (1) pin arrangement, (2) square key size and position, (3) circular shielding metal skirt notches & metallic additions - unlike the nonstandard mini-DIN connectors which may have directly overlapping characteristics to each other or to the standard mini-DIN connectors.
(plug or male connector shown, as visible when unplugged)
Several non-standard sockets are designed to mate with standard mini-DIN plugs. These connectors provide extra conductors, and are used to save space by combining functions in one connector that would otherwise require two standard connectors.
Other non-standard connectors mate only with their matching connectors, and are mini-DIN connectors only in the sense of sharing the 9.5mm plug body. These mini-DIN style plugs are not approved by the Deutsches Institut für Normung, the German standards body, and many applications could be considered proprietary.
(plug or male connector shown, as visible when unplugged; female sockets appear left-right reversed)
Many laptops and video cards use a 7-pin video output jack compatible with a standard 4-pin mini-DIN plug. Pins 1-4 use the standard S-video pinout, enabling standard S-video cables to connect directly. A wider key prevents insertion of the matching plug into a standard 4-pin socket.
The use of the extra three pins varies from manufacturer to manufacturer, but commonly includes a composite video output which is available using the manufacturer's proprietary adapter. Alternatively a YPbPr signal may be provided. Later Dell laptops provide an SPDIF audio signal. Some proprietary adapters bridge specific pins in order to enable the signal on other pins, or to specify the type of signal to be delivered.
The keying and pin arrangement prevents the use of the standard 7-pin mini-DIN plug, but even if a suitable plug can be obtained, use of non-proprietary adaptors on these ports may cause problems. Some graphics hardware, for example, is not engineered to have both the S-video and composite video outputs in use at once, and attempts to do this using non-standard adapters will produce poor results at best, and possible damage to the video output circuitry.
Some versions of the VIVO port on some ATI and Nvidia GeForce video cards used a 9-pin connector without the small metal bar to determine how the plug fit into the socket (instead, the 3 indentions in the outer ring were used.) See this link (4-connector version) as well as this link (6-connector version) for pinout mapping, and here for the ATI Radeon VIVO port pinout mapping.
The Apple GeoPort used a 9-pin jack compatible with either an 8-pin or a 9-pin mini-DIN plug, and was able to be used with devices designed for either the 8-pin mini-DIN Macintosh serial port connector, or the additional GeoPort protocols.
Apple pin numbering follows the 8-pin DIN assignments, for compatibility with earlier Macintosh serial ports using the standard 8-pin connector. The additional pin is numbered 9 by Apple, and corresponds to pin 5 of a 9-pin mini-DIN plug. It is used for a 5V 350mA power supply available to the peripheral. Pins 5-8 of the GeoPort socket and the mini-DIN-8 plugs used with it then correspond to pins 6-9 respectively of the standard mini-DIN-9 plug.