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SGI O2 General Maintenance

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SGI O2 with system module removed (Rules666)
An O2 with the system module slid out of the back. Always unplug the mains lead first (Rules666, CC BY-SA 4.0)

Routine care and service procedures for the SGI O2, from SGI's O2 Workstation Hardware Reference Guide (007-3275-002), its memory installation instructions and its site preparation guide, with notes from owners.[1][2][3] SGI's guide gives owner procedures for changing the system module, CPU modules, memory, system drive, audio-visual module, power supply and CD-ROM drive.[4] The parts that need attention now are the power supply and its fan, the DS1687 clock chip and the memory contacts.[5][6][7]

Warning: never remove or insert the system module with the mains lead plugged in. The supply keeps standby power on the system board, and pulling the module live can destroy the board.[8][6][9]

Environment

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O2 site requirements (SGI 007-3452-004, Tables 3-1 and 3-2)
Item Specification
Power 100–120 V or 200–240 V AC, single phase, 47–63 Hz
Maximum power 245 W from the wall
Heat 835 BTU per hour maximum
Airflow 37 cfm maximum
Operating temperature 10 to 35 °C, changing by no more than 10 °C an hour
Relative humidity 10% to 80% operating, non-condensing
Altitude 10,000 ft (3,048 m) operating

[3][10]

Air enters through both sides of the case and leaves through the back, so keep both sides and the rear clear.[11] The fan in the power supply is the only exhaust fan for the whole machine.[6]

Removing the system module

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SGI's procedure:[8]

  1. Switch off with the power button on the front.
  2. Unplug the power cable at the rear. SGI also suggests staying in one place while working, since walking across a room builds up static.
  3. The system module is on the left as you face the back. Pull down the lever on its left side.
  4. Slide the module out. The cables can stay connected if you handle it carefully.

To refit it, slide it back into the chassis. The PCI tray must be fully seated, or the module will not slide back in.[12]

Memory

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Banks A to D are pairs of DIMM sockets, socket 1 nearest the CPU. Fit the largest DIMMs in bank A, keep both DIMMs of a bank the same size, type and colour code, and fill the banks in order without gaps. Bank A must always be filled.[2]

  1. With the system module out and a wrist strap clipped to the chassis, hold the DIMM level over its socket.
  2. Push it straight down, gently but firmly, until it clicks and the latches on each side snap up.
  3. Check that the tops of the two DIMMs in each bank are level; one that sits higher is not fully seated.
  4. Refit the module, power on and check the memory size.[13][2]

SGI's colour codes identify each DIMM: purple 16 MB, yellow 32 MB, green 64 MB, silver 128 MB.[2] 128 MB DIMMs need PROM version 4.4 or later.[6] The TechPubs Wiki notes that O2 DIMMs are sensitive to dirt and shock, so clean and reseat them after a machine has been moved, and look for surface-mount parts knocked off the modules.[7]

CPU module

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For an R5000-class module:[12]

  1. Remove the system module, lift the PCI tray lever, push down slightly on the rear of the tray and lift the tray out.
  2. Put on the wrist strap and remove the two screws holding the module.
  3. Rock the module gently to free it. SGI warns that rocking it too hard bends the pins.
  4. Line up the connector under the new module with the one on the board and press down until it clicks. Refit the screws.
  5. Hook the PCI tray's hinge into its slot, lower it and push it down firmly until the lever returns.

The R10000 and R12000 modules sit under a large heat sink; SGI's procedure removes the system module's plastic faceplate as well as the PCI tray.[12]

Power supply

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SGI's procedure for changing the supply:[14]

  1. Switch off and unplug the power cable.
  2. Press the latch at the top of the bezel over the power supply; it swings out and lifts away.
  3. Slide the lever to the right to release the supply, then pull it out by its pull ring.
  4. Slide the new supply in until it stops, push the lever to the left until it clicks, and refit the bezel by its bottom tabs.

Opening the supply

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Raion's notes from taking an O2 supply apart:[5]

  1. The Panaflo fan is held by a plastic rivet, which he drilled out; another owner managed to remove the rivets without damage.
  2. Remove the five screws holding the side panel.
  3. Test the fuse for continuity first.
  4. Unplug the fan's two-pin connector and slide the fan out to reach the five screws and the earth lug that hold the boards. The boards come out as one unit with the system connector, whose two plastic studs are pressed in with pliers to free it from the frame.

The plastic latches of the connector housing go brittle with heat and age, and the connector can fall back into the supply; one owner recommends replacing the housing while the supply is open.[5] See SGI O2 Capacitor Replacement Guide for the capacitors.

Fan

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The original fan is a Panaflo FBA08A12U1A with a sleeve bearing that gets louder as it wears. Bukošek replaced his with an EBM Papst 8412N, and warns against quiet PC fans with low static pressure: they cool the supply but cannot pull air through the rest of the densely packed case.[6]

Fan comparison (Bukošek)
Fan Airflow (cfm) Static pressure (mm H₂O) Speed (rpm) Noise (dB)
Panaflo FBA08A12U1A (original) 46.9 4.8 3450 38.2
EBM Papst 8412N 40.6 4 3100 32.0
Noctua NF-A8 FLX 30 1.96 2000 16.1
Noctua NF-R8 31 1.4 1800 17.1
Arctic F8 31 1 2000 20

[6]

Clock chip

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The Dallas DS1687-5 sits under the PCI riser. Its internal battery is rated for about ten years; when it runs down the O2 loses its PROM settings unless it stays plugged in, and a failing chip can stop the machine switching on.[6] Fit a new DS1687-5 or DS1687-5IND+ from a reputable supplier. Pulled chips on auction sites have little battery life left, while a new chip keeps its battery disconnected until it is first programmed. Do not fit a DS1687-3, which is a 3.3 V part.[6][15]

After fitting the chip, following Bukošek:[6]

  1. Fit a jumper on the two pins next to the chip and start the O2.
  2. Press Esc, then 5, to reach the Command Monitor.
  3. Type resetenv, then setenv OSLoadFilename /unix. On an R10000 or R12000 machine, check that OSLoadPartition points at the right drive bay.
  4. Type init and let IRIX boot, which starts the chip's oscillator.
  5. Shut down IRIX, unplug the mains lead (the O2 will not switch off by itself while the jumper is fitted) and remove the jumper.

The Ethernet address is not in this chip on the O2, so it does not need to be re-entered.[6]

Checklist for a machine out of storage

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  1. Unplug the mains lead before touching the system module.[8]
  2. Inspect or recap the power supply before applying mains.[5]
  3. Clean and reseat the DIMMs, and check them for damaged parts.[7]
  4. Check that the supply fan turns freely and runs when the machine is on.[6]
  5. Watch the front LED and use the troubleshooting flow chart.[16]
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References

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  1. ↑ Silicon Graphics, O2 Workstation Hardware Reference Guide, 007-3275-002, 1996 (File:SGI O2 Workstation Hardware Reference Guide (007-3275-002).pdf).
  2. ↑ 2.0 2.1 2.2 2.3 Silicon Graphics, Silicon Graphics O2 Workstation Memory Installation Instructions, 007-3778-002, 1997, pp. 4–8 (File:SGI O2 Workstation Memory Installation Instructions (007-3778-002).pdf). DIMM kits, colour codes, bank rules, installation.
  3. ↑ 3.0 3.1 Silicon Graphics, Site Preparation for SGI 2000-Series, Origin Family, Onyx2, Octane, and O2, 007-3452-004, pp. 30–31, Table 3-1 (File:SGI Site Preparation for SGI 2000-Series, Origin, Onyx2, Octane and O2 (007-3452-004).pdf).
  4. ↑ SGI, 007-3275-002, chapter 5, pp. 109–172. Replaceable parts.
  5. ↑ 5.0 5.1 5.2 5.3 "O2 PSU disassembly and refurb", IRIX Network forums, January to May 2020, forums.irixnet.org. Raion's disassembly notes; brittle connector housing.
  6. ↑ 6.00 6.01 6.02 6.03 6.04 6.05 6.06 6.07 6.08 6.09 6.10 Andrej Bukošek, "SGI O2", Hardware collection, bukosek.si (retrieved 22 October 2026). Supply fan and comparison table, DS1687-5 replacement and procedure, standby power, PROM 4.4 for 128 MB DIMMs.
  7. ↑ 7.0 7.1 7.2 "O2", TechPubs Wiki, tech-pubs.net (revision of 21 September 2025). DIMM sensitivity to dirt and shock.
  8. ↑ 8.0 8.1 8.2 SGI, 007-3275-002, pp. 23–27. Removing the system module; caution to remove the power cable first.
  9. ↑ "What parts can you fry if removing a plugged O2 system module?", IRIX Network forums, 17 March 2024, forums.irixnet.org.
  10. ↑ SGI, 007-3452-004, pp. 31–32, Table 3-2.
  11. ↑ SGI, 007-3452-004, p. 29, Figure 3-2. O2 airflow.
  12. ↑ 12.0 12.1 12.2 SGI, 007-3275-002, pp. 111–118. Replacing the R5000 and R10000 CPU modules; PCI tray.
  13. ↑ SGI, 007-3275-002, pp. 28–33. Installing and checking memory modules.
  14. ↑ SGI, 007-3275-002, pp. 143–151. Replacing the power supply.
  15. ↑ "Possible run of Octane&O2 Dallas RTC replacement PCB modules", IRIX Network forums, weblacky, 17 July 2019, forums.irixnet.org. DS1687-5IND+ still available.
  16. ↑ SGI, 007-3275-002, pp. 97–98, Figures 4-1 and 4-2. Diagnostic flow charts.


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