SGI Indigo2

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An SGI Indigo² IMPACT R10000

The SGI Indigo² and the SGI Challenge M were Unix computers marketed by SGI from 1993 to 1997, with production of IMPACT models ending in 1998. The Indigo² was a desktop workstation while the Challenge M was a server which differed from the Indigo² only by a slightly differently colored and badged case, and the absence of graphics and sound hardware. Both systems were based on the MIPS processors.

Both systems supported EISA and GIO64 expansion buses via a riser card. Indigo² systems also supported SGI IMPACT graphics hardware. The IMPACT graphics boards draw more power than the GIO-64 bus can deliver, so the IMPACT-ready systems have additional power connectors on the expansion riser card, with a separate connection to the power supply. An IMPACT-ready Indigo² must have an IMPACT-ready riser card, an IMPACT-ready power supply, and a sufficiently recent PROM revision.

System Architecture

CPU Options

The Indigo² has three distinct variants, each with a specific motherboard and "IP" number or designation:

  • IP22 supports an R4000, R4400, or R4600 CPU clocked at 100-250MHz
  • IP26 supports the R8000 CPU clocked at 75MHz
  • IP28 supports the R10000 CPU clocked at either 175 or 195MHz

IP26 systems were typical referred to as POWER Indigo2, while the IP28 systems usually had a grill badge that read "10000."

Memory Subsystem

All three variants had 12 SIMM slots on the motherboard, organized into three banks of four slots each, and took industry standard fast page mode (FPM) 72 pin SIMMs with parity. Speeds should be 60 or 70 nanoseconds, and the internal organization must be 36 bits wide - 8MB x 72 bit parts will not work.

IP22 systems will support up to 384MB with 32MB SIMMs. While the IP26 and IP28 systems both support 64MB SIMMs, published limits for these systems reflected concerns about the amount of heat generated by then-current DRAM chips. According to SGI the R8000-based IP26 systems would only support 640MB (2 banks of 256MB, one of 128MB), while the R10000-based IP28 would support 768MB (3 x 256MB).

Eventually 64MB SIMMs became available that generated less heat, and denser 128MB SIMMs became available. Both the IP26 and IP28 can use these 128MB SIMMs, but with limitations. IP26 systems require some banks to use lower-profile SIMMs to clear the CPU carrier, and SGI described limits on the mix of different density SIMMs in these systems. However owners have reported working configurations of up to 896MB (1 x 128MB, 1 x 256MB, 1 x 512MB bank).

With the IP28 it is possible to achieve a total of 1GB of RAM (2 banks x 512MB, or 2 x 256MB + 1 x 512MB), but unfortunately this appears to be a hard limit based on address logic.

(Much of this information was taken from Ian Mapleson's Indigo2 GigaRAM page. Thanks also to Bert Heise, Roger Garcia and David Cummings.)

Compatible 128MB SIMMs

A number of mainstream servers used 128MB SIMMs that are compatible with the Indigo2. Here is a list of models:

  • HP/Compaq NetServer LX Pro 6/166
  • HP/Compaq NetServer LX Pro 6/166 SMP
  • HP/Compaq NetServer LX Pro 6/200
  • HP/Compaq NetServer LX Pro 6/200 SMP
  • HP/Compaq NetServer LXe Pro 6/166
  • HP/Compaq NetServer LXe Pro 6/200
  • HP/Compaq NetServer LXr Pro 6/200
  • IBM PC Server 704 (8650-4MO)
  • IBM PC Server 704 (8650-5MO)
  • IBM PC Server 704 (8650-6MM)

Nekochan member smj found that HP part number D4893A was a reliable search term for finding compatible parts on eBay circa 2010.


The graphics boards available for the Indigo² were the pre-IMPACT Newport and Express boards (which included the SGI XL24, SGI XZ, SGI Elan and SGI Extreme) and the MGRAS IMPACT boards (the SGI Solid IMPACT, the SGI High IMPACT, the SGI High IMPACT AA, and the SGI Maximum IMPACT). IMPACT graphics is not supported by the Power Indigo² (R8000 CPU). The Indigo2's replacement, the SGI Octane, offered an upgraded bus but featured the same graphics options, albeit in repackaged form.

Identifying Indigo2 Graphics Options

Most Indigo2 graphics options can be identified easily by looking at the rear panel of the machine. First generation graphics options (XL/Newport and Express) have a round 3-pin mini-DIN connector for stereo glasses. XL/Newport can be differentiated from XZ or Extreme as the Express graphics options (XZ or Extreme) have a small mini-BNC genlock connector in addition to the stereo port and the 13W3 monitor connector.

XZ (2x GE7) can not be differentiated from XZ-Elan (4x GE7) without the machine running as the boards are exactly the same, with the XZ-Elan having 4 GE7 chips packaged in the GE7 MCM, whereas the original XZ had 2 empty wells.

Extreme graphics has 3 boards which you should be able to discern through the ventilation grating next to the slots.

IMPACT-class graphics have the 13W3 and a DE-9 connector for the stereo glasses. The class of graphics is easier to determine in IMPACT because the DE-9 is on the base board, whereas the 13W3 connector is on the top board.

Solid IMPACT graphics (1 board) have both the 13W3 and the DE-9 on the same board.

High IMPACT is a two board set, with the DE9 underneath the 13W3. It is impossible to tell from the back whether it is a High-AA IMPACT or not (High-AA IMPACT boards have two GE11 Geometry Engines whereas original High IMPACT boards come with a single GE11. The relationship is the same as the relationship of original XZ to XZ-Elan). If the cover can be removed, the High-AA IMPACT will have two large PGA chips on the lower board, whereas the original High IMPACT will have one large PGA chip and one empty pad.

Maximum IMPACT is a three-board set, so there will be a blank rear plate between the DE-9 and the 13W3.

There is no way of determining whether or not the High IMPACT and Maximum IMPACT boards have the 4MB Texture RAM expansion option installed or not from the outside. If you can open the Indigo2, you can look at the top board to see if the expansion module is present or not.

As always, if the system is operational, hinv and /usr/gfx/gfxinfo will give you complete information on the system hardware and graphics subsystem.

Graphics Troubleshooting

Please see the Troubleshooting and Repair section below.

I/O Subsystem

  • PS/2 Mouse and Keyboard ports
  • One 10Mbps 10baseT Ethernet interface, with AUI and RJ45 connections
  • Two RS422 serial ports (mini-DIN, to 38.4kbps)
  • One bi-directional parallel port
  • IRIS Audio (up to 48KHz sampling on inputs)
  • Two 10MBps SCSI controllers (WDC 33C93B)
  • EISA expansion bus (4 slots for Extreme gfx, 3 for IMPACT)
  • GIO64 expansion bus (3 slots for Extreme, 4 for IMPACT)
  • One 5.25" SCSI drive bay (externally accessible)
  • Two 3.5" SCSI drive bays (one externally accessible)

Note that the EISA and GIO slots are interleaved on the same riser, so all may not be occupied at the same time.

ATM, FDDI, Fibrechannel, HPPI, and Token Ring interfaces were available from various vendors for either the EISA or GIO bus. At least one GIO64-VMEbus adapter was offered (Bit3).

Internal Drives

The internal drive bays of the Indigo2 take model-specific carriers. These carriers mate to a backplane using a non-standard connector, and contain devices using a standard 50 pin IDC ribbon cable connector. There may not be enough room in the carrier to use an adapter board to use 68 or 80 pin devices unless using a down-sized device, e.g. a 2.5" hard drive in a 3.5" drive carrier.

Faster Ethernet Options

In addition to the 10Mb Ethernet controller on the motherboard, there were several 100Mb LAN options available from 3rd parties, either via EISA or GIO64 expansion cards. The two best known and most widely used Indigo2 network cards are 3Com 3C597-TX 100Mbit EISA Card, and the Phobos G160 GIO64. The second one offers better overall performance due to using the superior GIO64 bus, which also has the effect of reducing the CPU utilization through use of DMA transfers.

Motherboard I/O Connector Pinouts

Indigo2 io backplane pinout.jpg

Add-On Options

Digital Media



Operating Systems

Versions of IRIX

The Indigo2 was initially delivered with IRIX 4D1-4.x. Support for the Indigo2 finally ended with IRIX 6.5.22.

Support for the Indigo2 IMPACT was available with point releases of IRIX 5.3 and IRIX 6.2. Patches to IRIX 6.2 were also shipped with the addition of the R10000 CPU option.

Important Patches

IRIX patch 7009 is best known for fixing an upgrade/installation bug with rqsall(1m) under 6.5.22 (and possible 6.5.21) on systems featuring R8000-based IP21 or IP26 boards. These are usually found in the POWER Indigo2 and POWER Onyx workstations. The key to upgrading these systems to 6.5.22 is to make sure patch 7009 is applied before you run rqsall(1m) at the end of your installation. This way the corrected rqsall(1m) will be used to setup the system for reboot.

See the thread reference here for additional details.


Linux was ported to the Indigo2 along with other SGI models of the Indy-Indigo2-Octane period. More information can be found on the Linux/ wiki, specifically on their IP22 page, a catch-all for SGI hardware from this period.

XL graphics were commonly supported by distributions in the 2.4 kernel timeframe. A driver for IMPACT graphics and patches for XFree86 and servers are available courtesy Peter Fuerst.

Troubleshooting and Repair

Power Supply

The machine may refuse to power up at all, though the fans move briefly when the power switch is thrown. Or the machine to switch off at random, regardless of whether the environment is warm or cold. Briefly disconnecting the machine from the electrical outlet may clear the condition for a time. According to this article the problem may be bad capacitors in the high-voltage section of the power supply.

Note that the article describes a procedure working with high-voltage electronics, and could be dangerous.

Impact Graphics TRAM: Troubleshooting, Installation and Removal

Member Ian Mapelson has shared detailed instructions for testing, installing, and removing TRAM modules for IMPACT graphics boardsets in this forum post.

External Links

SGI Documentation:

More information can be found at: