6 pin mini-DIN female (PS/2 STYLE) connector at the computer.
The SGI IRIS Indigo workstation (introduced around 1991) uses a proprietary 6-pin mini-DIN keyboard connector that shares the same physical shell as the later PS/2 standard but is electrically incompatible with it. The connector carries both keyboard and mouse serial data on a single cable: the mouse attaches to a second, identically wired 6-pin mini-DIN port on the side of the keyboard rather than directly to the chassis. Supply voltage on pin 4 varies by CPU: Indigo R3000 systems deliver +8 V, whilst Indigo R4000 systems deliver +12 V, with a maximum rated current of 1 A. Later SGI platforms (Indigo2, Indy, O2, Octane, and Onyx) switched to standard PS/2-compatible ports and must not be confused with this proprietary interface.
| Pin | Name | Description |
|---|---|---|
| 1 | KRCD | Keyboard Receive |
| 2 | MRCD | Mouse Receive |
| 3 | GND | Ground |
| 4 | PWR+ | Power +8V |
| 5 | KTXD | Keyboard Transmit |
| 6 | N/C | Not Connected |
Signals
- KRCD — Serial data received by the host from the keyboard (input to host).
- MRCD — Serial data received by the host from the mouse, routed through the keyboard cable (input to host).
- GND — Signal and power ground.
- PWR+ — Supply voltage to the keyboard: +8 V on Indigo R3000 systems, +12 V on Indigo R4000 systems; maximum 1 A.
- KTXD — Serial data transmitted from the host to the keyboard (output from host).
- N/C — Pin 6 is not connected on Indigo systems.
Notes
- This connector is NOT PS/2 compatible despite using the identical 6-pin mini-DIN shell. Connecting a PS/2 keyboard or mouse to an Indigo keyboard port, or vice versa, risks hardware damage due to voltage incompatibility.
- The mouse does not connect directly to the workstation chassis. It plugs into a second 6-pin mini-DIN socket on the keyboard body; both sockets on the keyboard are wired identically.
- Pin 4 power voltage is platform-dependent: +8 V (Indigo R3000) or +12 V (Indigo R4000). The table above reflects the R3000 value.
- Indigo2, Indy, O2, Octane, and Onyx systems use PS/2-compatible 6-pin mini-DIN ports (pin 1 Data, pin 5 Clock, +5 V on pin 4) and are a separate, standard interface.
References
- IRIS Hardware Developer Handbook (keyboard/mouse interface, Table 4-13) — Silicon Graphics, Inc.
- IRIS Indigo Owner’s Guide, document 007-9065-050 (Table A-5) — Silicon Graphics, Inc.