Personal Computer PC AT Form Card Bus Description and Pinout

AT Form card

AT to ATX Motherboard Card Extension

AT Form Card Description

The AT Form Card may not appear as a card at all, but translates the header interface on a AT style Motherboard into an I/O connector. The AT Form Card may appear as a Riser type card or a connector/cable type arrangement. The AT form factor motherboard did not define the I/O connectors as well as the Baby-AT or ATX mother boards did. The ATX mother board defines the location, placement and type of rear panel I/O, while the AT motherboard did not. The AT motherboard was obsolete as off 1997 when the ATX mother board was produced. So, by extension, the AT Form card is also obsolete and no longer required by any new form factor mother board.

There are a number of interfaces which exist on the AT motherboard which appear not to be taken to the case I/O. To gain access to these interfaces an AT Form Card is required. The motherboard contains a dual-in-line header which may be accessed, by the AT Form Card. The AT Form Card may consist of a board which plugs into the header and translates the I/O out the back panel, or a Header connector [to interface to the header on the motherboard].

The board solution is straight forward, connecting into the header and bringing connectors to the back panel, as a normal expansion card would. The IDC Header solution would translate to a ribbon cable which is then translated to connectors on the back-panel I/O. The back-panel I/O consists on the standard blank metal panel covering the I/O expansion slots at the rear of the computer. The connectors which are provided on the metal I/O panel include two USB connectors, a PS2 connector and an Infrared output. The AT motherboard header is a 2-pin [row] x 9-pin (18 pins) flat cable connector.

**AT Form Card Connector Pinout**
Pin #	Signal Function	Pin #	Signal Function
1	USB +1 5vdc	10	Key Pin
2	USB +2 5vdc	11	Mouse Clock
3	USB -1 Data	12	Mouse Data
4	USB -2 Data	13	Ground
5	USB +1 Data	14	Ground
6	USB +2 Data	15	IR Hi
7	Ground	15	IR Input
8	Ground	17	IR, +5vdc
9	PS/2 +5vdc	18	IR Output

This is basically a cable assembly, so there is no obsolescence issue as with an AT card.
But at the same time, I normally don't see these installed on computers.
Of course as there are no longer any AT expansion boards, there would be no need to have an AT translator cable.


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