9 pin D-SUB male connector at the computer.
9 pin D-SUB female connector at the cable.
The SGI 9-pin serial port is a DB-9 EIA-232 (EIA-423) interface fitted to Silicon Graphics workstations and servers of the late 1980s and 1990s, including the Personal IRIS 4D-series, Challenge, Onyx, and Power Series. Unlike the IBM PC/AT DB-9 serial port, SGI uses a female DB-9 connector on the system unit, making standard PC serial cables incompatible. The port supports asynchronous communication at up to 38,400 baud and carries the standard EIA-232 modem-control signals, though pins 1 and 6 are left unconnected.
| Pin | Name | Description |
|---|---|---|
| 1 | N/C | Not Connected |
| 2 | TD | Transmit Data |
| 3 | RD | Receive Data |
| 4 | RTS | Request To Send |
| 5 | CTS | Clear To Send |
| 6 | N/C | Not Connected |
| 7 | SG | Signal Ground |
| 8 | DCD | Data Carrier Detect |
| 9 | DTR | Data Terminal Ready |
Signals
- N/C — Not connected; pins 1 and 6 are reserved and carry no signal.
- TD — Transmit Data; serial data output from the SGI system (DTE).
- RD — Receive Data; serial data input to the SGI system.
- RTS — Request To Send; handshaking output asserted by the SGI system.
- CTS — Clear To Send; handshaking input from the remote device.
- SG — Signal Ground; common reference for all EIA-232 signal levels.
- DCD — Data Carrier Detect; input indicating an active carrier from the modem.
- DTR — Data Terminal Ready; output indicating the SGI system is powered and ready.
Notes
- The system-side connector is a female DB-9; the cable plug is male. This is the reverse of the IBM PC/AT convention, so standard PC serial cables cannot be used directly.
- Signal levels conform to EIA-423 (TIA/EIA-423-B), which is backwards-compatible with EIA-232. Voltage swing varies by model: the Indigo operates at ±5 V, whilst the Indy and Indigo2 use ±9 V for improved noise immunity.
- The EIA-422 (balanced differential) variant of this DB-9 port, found on some SGI systems, uses a completely different pin assignment (DTR on pin 1, differential TX/RX pairs on pins 2/3/7/8, RTS on pin 9) and is not covered here.
- O2, Octane, Onyx2, and Origin 2000 systems use the standard IBM PC/AT-compatible DB-9 male pinout and are not covered by this page.
References
- SGI Hardware Developer Handbook — Interfaces: Serial Ports, Silicon Graphics, Inc. (Developer Forum, 1995), Table 4-3: DB-9 EIA-232 serial pinout.
- Getting 422 In and Out of Your SGI – Lurker’s Guide (lurkertech.com, citing IRIX man serial(7))