SGI O2 Troubleshooting Guide
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Fault-finding on the SGI O2, from the troubleshooting chapter of SGI's O2 Workstation Hardware Reference Guide (007-3275-002), with power supply data from the TechPubs Wiki and repair reports from owners.[1][2] SGI's flow charts end at the replaceable module. Before opening anything, unplug the mains lead: removing or inserting the system module with power connected damages the system board.[3][4]
Front LED
[edit | edit source]SGI's first flow chart reads the LED on the front of the machine:[5]
| LED or symptom | Possible cause | First action | Solution |
|---|---|---|---|
| No LED | No power; power supply failure | Check the power connections | Replace the power supply |
| Solid red | CPU module failure | Reseat the CPU module | Replace the CPU module |
| Solid amber | System board failure | Reseat the CPU module and the DIMMs | Replace the system board |
| Blinking amber | Memory diagnostic failure | Check that DIMM slots 1 and 2 are filled; reseat the DIMMs | Replace the DIMMs |
| No boot tune | Volume too low, headphones plugged in, or speaker failure | Turn up the volume; check for headphones | Replace the system board or the chassis |
| Solid green | Diagnostics passed | Record any error message | – |
SGI's second chart covers a machine that reaches a green LED but has no display, keyboard, mouse, system drive or CD-ROM drive. Its first steps are to check the cable and connection, the monitor's power, power-saving mode and brightness, and that the system drive's locking lever is pushed fully up; after that it points to the cable, the monitor, the device or the system board.[5]
No LED
[edit | edit source]- Check the mains lead and outlet, then the power supply.[5]
- The DS1687 clock chip switches the O2 on when the power button is pressed, so a failing chip can stop the machine starting, or let it start only some of the time. Bukošek sometimes had to start his O2 by fitting a jumper across the two pins beside the chip before he replaced it.[6]
- A supply whose output capacitors have failed can be dead. One owner brought a failed supply back by replacing the six largest output capacitors.[7]
Testing the supply on the bench
[edit | edit source]Elf's measurements on the TechPubs Wiki, for a Sony APS-90 supply (SGI 060-0022-001):[2]
- The 3.3 V standby output is present whenever mains is connected. The supply itself only starts when the run line (pin 2) is grounded, unlike the Indy and Indigo² supplies.
- The two sense lines must be connected for a bench test: pin 1 to the +3.43 V rail and pin 13 to 0 V. Without them the +3.43 V output swings above 5 V and the supply tends to shut down under load.
- Power good (pin 14) rises to 3.3 V logic level some time after the +3.43 V and +5.1 V rails have settled.
| Pin | Function | Pin | Function |
|---|---|---|---|
| 1 | +3.43 V sense | 13 | 0 V sense |
| 2 | Run (ground to start) | 14 | Power good (3.3 V logic) |
| 3, 4 | +5.1 V | 15 | +3.3 V standby |
| 5 to 9 | 0 V | 16 | +12 V |
| 10 to 12 | +3.43 V | 17 | −12 V |
| – | – | 18 to 21 | 0 V |
| – | – | 22 to 24 | +3.43 V |
| Rail | Rating |
|---|---|
| +3.43 V | 31 A |
| +5.1 V | 10 A |
| +12 V | 3.2 A |
| −12 V | 0.25 A |
| +3.3 V standby | 10 mA |
[2] Most of the O2's load is on the +3.43 V rail, unlike the Indy and Indigo², which draw mostly from +5 V.[2]
Red or amber LED
[edit | edit source]- Solid red after the system module was pulled or inserted with the mains lead connected usually means the system board has been damaged; the CPU, memory and other modules generally survive.[4]
- Random memory errors, or a machine that will not boot with a solid red or blinking amber LED, are often poorly seated or dirty DIMMs, especially after the machine has been shipped. Clean and reseat them, and check them for knocked-off surface-mount parts.[8]
- Blinking amber: bank A (slots 1 and 2) must hold a matched pair, every bank must hold two DIMMs of the same size and type, the largest go in bank A, and no bank may be skipped.[5][9]
Burnt component on the system board
[edit | edit source]An O2 that would not boot had a component burst off the system board near the memory, taking a pad with it. Forum members identified it as a surface-mount resettable fuse at U1, a Raychem SMD150-2 PolySwitch, which weblacky noted holds between 1 and 1.75 A at room temperature. The cause was not found; replacements are available as old stock.[10]
Clock chip
[edit | edit source]A flat DS1687-5 makes the O2 forget its PROM settings whenever it is unplugged, because standby power keeps the chip alive while the lead is connected. Bukošek's chip had also developed a drifting crystal and needed frequent time corrections.[6] The Ethernet address on the O2 is held on the PCI riser, not in the clock chip.[6][8] For replacing the chip, see General Maintenance.
CD-ROM drive
[edit | edit source]The Toshiba CD-ROM drives fitted to many O2s split a small press-fit nylon gear on the tray motor; the tray then refuses to open or to stay closed, or the drive reports a misload and ejects. Push the gear back onto the shaft and fix it with a little glue. To avoid stressing the mechanism, close the tray with the inject command; do not push it shut.[8]
Diagnostics
[edit | edit source]Power-on, confidence and IDE tests
[edit | edit source]The power-on tests run at every start; a failed part shows as a red LED and usually an error message.[11] The confidence tests (Toolchest, System, Confidence Tests) check the mouse, keyboard, monitor, audio, external SCSI devices other than disks, Presenter and ISDN.[11] For the IDE tests, which take 30 to 45 minutes:[11]
- Switch off, wait a few seconds and switch on.
- At the System Startup notifier click Stop for Maintenance or press Esc.
- Choose Run Diagnostics, or type 3. Esc stops the tests at any point.
- Read the result, then press Enter and Esc to return to the menu.
If the System Maintenance menu cannot be reached, SGI's guide says the system is faulty; if the diagnostics will not run, the disk may be faulty.[11]
Forgotten PROM password
[edit | edit source]Remove the system module and the PCI tray, put on a wrist strap, and move the jumper on the system board to the password position shown in SGI's Figure 4-11. The pin location is the same on R5000 and R10000 boards.[12]
Related pages
[edit | edit source]- SGI O2
- SGI O2 General Maintenance
- SGI O2 Capacitor Replacement Guide
- SGI O2 Documentation
- SGI O2+
- Capacitor Failure Symptoms
References
[edit | edit source]- ↑ Silicon Graphics, O2 Workstation Hardware Reference Guide, 007-3275-002, 1996, chapter 4, pp. 97–108 (File:SGI O2 Workstation Hardware Reference Guide (007-3275-002).pdf).
- ↑ 2.0 2.1 2.2 2.3 2.4 "O2 Power Supply Information", TechPubs Wiki, based on measurements posted by SGUG forum member Elf, tech-pubs.net (revision of 27 September 2025). Connector pinout, ratings, run, sense and power-good behaviour.
- ↑ SGI, 007-3275-002, pp. 23–26. Caution to remove the power cable before removing the system module.
- ↑ 4.0 4.1 "What parts can you fry if removing a plugged O2 system module?", IRIX Network forums, weblacky, 17 March 2024, forums.irixnet.org.
- ↑ 5.0 5.1 5.2 5.3 5.4 SGI, 007-3275-002, pp. 97–98, Figures 4-1 and 4-2. Diagnostic flow charts.
- ↑ 6.0 6.1 6.2 Andrej Bukošek, "SGI O2", Hardware collection, bukosek.si (retrieved 22 October 2026). DS1687-5 functions and failure, jumper start, system ID chip.
- ↑ "O2 PSU disassembly and refurb", IRIX Network forums, 15 May 2020 post, forums.irixnet.org. Failed supply repaired with six new output capacitors.
- ↑ 8.0 8.1 8.2 "O2", TechPubs Wiki, tech-pubs.net (revision of 21 September 2025). Memory contact faults, CD-ROM gear, Ethernet address on the PCI riser.
- ↑ Silicon Graphics, Silicon Graphics O2 Workstation Memory Installation Instructions, 007-3778-002, 1997, p. 5 (File:SGI O2 Workstation Memory Installation Instructions (007-3778-002).pdf). Bank rules.
- ↑ "O2 not booting", IRIX Network forums, 4 August 2020, forums.irixnet.org. Burst PolySwitch at U1, identified as a Raychem SMD150-2.
- ↑ 11.0 11.1 11.2 11.3 SGI, 007-3275-002, pp. 99–100. Power-on, confidence and IDE tests.
- ↑ SGI, 007-3275-002, pp. 104–108, Figures 4-10 and 4-11. Disabling the System Maintenance password.