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SGI IRIS 4D General Maintenance

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SGI Professional IRIS twin-tower workstation (Seiya Ishibashi)
A Professional IRIS: card cage tower on the left, drive and power supply tower on the right (Seiya Ishibashi, CC BY 2.0)

Care and service notes for the SGI IRIS 4D twin-tower Professional IRIS machines (4D/50, 4D/60, 4D/70, 4D/80 and 4D/85), which have no separate page, with notes that apply across the IRIS 4D family. The other 4D lines have their own guides: SGI Personal Iris General Maintenance, SGI Indigo General Maintenance and SGI Crimson General Maintenance; for the Power Series see SGI Power Series. No SGI service documentation for the Professional IRIS was found, so these notes come from owners who have restored the machines, chiefly jan-jaap's work on a 4D/70 GT and a 4D/50 G.[1][2]

Warning: the power supply is rated at up to 200 A on its 5 V output. Switch off at the circuit breaker and unplug the machine before opening either tower.[1][2]

Keyboard and mouse

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Use only an SGI keyboard and mouse of the right type. The Professional IRIS uses a DE-15 keyboard connector, and the mouse plugs into the keyboard. Wikipedia warns that IRIS and PS/2 keyboards use incompatible voltage levels, and that plugging one into the other's port can damage the keyboard, the computer or both.[3]

The two towers

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The larger tower holds the 12-slot VME card cage and the smaller one the drives, with the power supply in its base.[3][2] The skins are white plastic painted brown, and the paint chips.[1]

  • Both towers have an intrusion switch. Opening a tower trips the circuit breaker and cuts power to the system; jan-jaap used a toothbrush to hold one closed while running the machine with its panels off.[2]
  • The mains inlet and circuit breaker are in a metal box that comes out and plugs into the supply's wiring harness. The supply needs an external fuse, so three heavy mains cables run to it: one from the inlet, and two back to the breaker. Another owner's 4D/70 G had a Hubbell twist-lock mains inlet in place of the IEC inlet on jan-jaap's 4D/50; jan-jaap believes the twist-lock was used in 110 V countries.[2]
  • The chassis has centrifugal blowers. One had failed in jan-jaap's 4D/70 GT; he replaced the motors of both, and thinks the dead blower was probably related to the burnt-out graphics raster manager boards he found.[1]

VME backplane jumpers

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On the Professional IRIS the VME bus is the system bus, so the backplane jumpers have to be right. Two VME signals, interrupt acknowledge (IACK) and bus grant (BG), are passed from card to card down the backplane, and an empty slot must have jumpers fitted to carry them on to the next card.[1] Wrong jumpers gave jan-jaap a kernel panic, from a bus error in the VME interrupt handler, whenever the graphics started.[1]

  • The jumpers are on the reverse side of the backplane, at the front of the machine: remove the front skin panel and open the card cage's front panel to reach them.[1]
  • SGI's Hardware Developer's Handbook, as quoted by jan-jaap, gives this layout for a GT system: slot 1 IP4 processor, 2 Ethernet, 8 GE, 9 GM, 10 RM, 11 RV, 12 RM.[1]
  • The 4D FAQ that jan-jaap quotes makes the GE4 slot the one exception: it is jumpered even with the board fitted. Taking the handbook literally, he jumpered every slot except slot 1 (IP4), slot 6 (the Ethernet board, moved there) and slot 9 (GM1). The FAQ notes that slot 6 has a different VME P2 connection to the processor board from slot 2.[1]
  • Another forum member noted that the GF3 is the only Clover 1 graphics board that uses the VME bus; the others talk to it over the P2 and P3 connectors and a front interconnect.[2]

Boards and contacts

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  • Check the VME insertion handles. A 12.5 MHz IP4 with broken handles did not make proper contact with the backplane, and the machine showed no sign of its graphics until a board with good handles was fitted.[2]
  • The DE3 board's VRAM modules are SGI's own design with dual-ported chips. jan-jaap cleaned the sockets and modules with pure alcohol and treated the contacts with DeoxIT Gold, after which the display board test passed and the stripes on the screen were gone.[2]

Power supply

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The original supply is an LH Research "Mighty Mite". jan-jaap gives its main +5 V output as 200 A, and the unit in his 4D/50 as 1000 W.[1][2] Thick cables run from the supply to the backplane, with sense wires that let the supply correct for the voltage drop along them.[1]

  • jan-jaap measured a drop of about 50 mV between the supply and the backplane of his 4D/70.[1]
  • With the sense wires connected, his repaired supply oscillated at about 2 to 2.5 kHz under the machine's load and made a loud noise. He disconnected the sense wires and set the output to 5.05 V, which gave exactly 5.00 V at the backplane. He notes this works only because the machine's configuration, and so its load, does not change.[1][4]
  • The supply did not start on the bench until it had a load on the 5 V rail; its built-in load resistors were not enough, and 10 A from an electronic load was.[2]
  • Before repairing the original, jan-jaap ran his 4D/70 for some years on a Power-One SPM5-series supply, without the sense feedback.[1]

See SGI IRIS 4D Capacitor Replacement Guide for work inside the supply.

NVRAM and PROM settings

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The IP4 board keeps its PROM settings in battery-backed memory with two batteries inside. On jan-jaap's 4D/70 it was dead, and since resetenv does not work on this PROM, he had to boot with a serial console and enter the settings by hand at every power-on.[1] CB_HK's write-up on rebuilding the Crimson's Dallas NVRAM module with a coin cell was offered for the same problem.[1] The settings he used on his 4D/70 GT:[1] 

netaddr=192.0.2.1
dbaud=9600
rbaud=1200
bootfile=dksc(0,1,8)sash
bootmode=m
console=G
root=dks0d1s0
keybd=df
monitor=60
sync_on_green=y
diskless=0
path=dksc(0,1,8)
dbootfile=/stand/ide

The PROM checks the monitor value: an Indy-style value such as h produced an error when the graphics started, and unsetenv monitor set it back to 60.[1] To force the console onto the first serial port, disconnect the keyboard and mouse, or set console=d.[1]

Drives and software

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  • The system disk is set to SCSI ID 1 by a jumper on the drive.[2]
  • One owner found that IRIX 4 would not change run level, shut down or boot normally on a machine with no network interface. He fitted a VME ENP-10 Ethernet board, after which the system behaved.[2]
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References

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  1. ↑ 1.00 1.01 1.02 1.03 1.04 1.05 1.06 1.07 1.08 1.09 1.10 1.11 1.12 1.13 1.14 1.15 1.16 1.17 1.18 "Looking for help with a Professional IRIS", IRIX Network forums, jan-jaap and others, December 2018 to February 2022, forums.irixnet.org. 4D/70 GT: VME jumpers, blowers, skins, LH Research supply repair and sense wiring, NVRAM and PROM settings.
  2. ↑ 2.00 2.01 2.02 2.03 2.04 2.05 2.06 2.07 2.08 2.09 2.10 2.11 "Professional IRIS 4D/50, Clover 1 graphics", IRIX Network forums, jan-jaap and others, June to August 2025, forums.irixnet.org. 4D/50: supply location and start-up load, intrusion switches, mains wiring, insertion handles, VRAM contacts, IRIX without a network interface.
  3. ↑ 3.0 3.1 "SGI IRIS", Wikipedia, en.wikipedia.org (revision of 14 June 2026). Twin-tower layout, keyboard connectors and the PS/2 warning.
  4. ↑ "LH Research - research", IRIX Network forums, jan-jaap and others, April 2022, forums.irixnet.org. Sense feedback oscillation in the Professional IRIS supply.


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