The ATX form factor card is an optional riser card that bridges AT-class motherboards to ATX-standard external I/O, providing USB, PS/2 mouse, and IrDA infrared ports from a header on the motherboard. Intel’s ATX Specification (first published in 1995, revised through Version 2.01 in 1997) established the ATX board layout and I/O shield standard as the successor to Baby-AT; the riser card allowed AT-form-factor boards to populate the same rear panel without a full board redesign. The header carries power, data, and control signals for up to two USB ports, a PS/2 mouse port, and a SIR-compliant IrDA infrared port, all on a single connector.
| Pin | Name |
|---|---|
| 1 | USB +5V |
| 2 | USB Port 0 - |
| 3 | USB Port 0 + |
| 4 | GND |
| 5 | n/c |
| 6 | PS/2 Mouse CLK |
| 7 | GND |
| 8 | IR Receive |
| 9 | +5 V |
| 10 | USB +5V |
| 11 | USB Port 1 - |
| 12 | USB Port 1 + |
| 13 | GND |
| 14 | n/c |
| 15 | PS/2 Mouse DTA |
| 16 | GND |
| 17 | IR Receive |
| 18 | IR Transmit |
Alternative Pinout
| Pin | USB 1 | USB 2 | PS/2 Mouse | Infrared |
|---|---|---|---|---|
| 1 | +5V DC | " " | ||
| 2 | +5V DC | |||
| 3 | Data - | |||
| 4 | Data - | |||
| 5 | Data + | |||
| 6 | Data + | |||
| 7 | Ground | |||
| 8 | Ground | |||
| 9 | +5V DC | |||
| 10 | ||||
| 11 | Mouse Clk | |||
| 12 | mouse Data | |||
| 13 | Ground | |||
| 14 | Ground | |||
| 15 | IR Hi | |||
| 16 | Id in | |||
| 17 | +5V DC | |||
| 18 | IR Out |