Indigo 2

A teal Indigo2
A teal Indigo2

The Indigo 2, codenamed "Fullhouse" is a high end workstation marketed by Silicon Graphics from 1993 to 1997, with production of IMPACT models ending in 1998. The Indigo 2 succeeded the earlier IRIS Indigo line and is the higher end version of the Indy.


The Indigo 2 is a large teal or purple desktop that is deceptively heavy, around 40lbs. It came with two plastic feet which can be used to set it upright vertically.


The Indigo 2 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 generally referred to as the POWER Indigo 2, while the IP28 systems usually had a grill badge that read "10000."

An R10k Indigo2
An R10k Indigo2


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.


The graphics boards available for the Indigo 2 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 Indigo 2 (R8000 CPU). The Indigo2's replacement, the SGI Octane, offered an upgraded bus but featured the same graphics options, albeit in repackaged form.

The IMPACT units are purple, though it is feasible to upgrade a teal Indigo 2 with proper upgrade parts.An IMPACT-ready Indigo 2 must have an IMPACT-ready riser card, an IMPACT-ready power supply, and a sufficiently recent PROM revision.


For networking, the Indigo 2 has an on-board AUI and a 10Mb Ethernet jack. The AUI and Ethernet cannot be used at the same time, the Ethernet jack takes priority automatically. 10/100Mb cards are available on the used market for faster connection speeds. This is near identical to the Indy's configuration.


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.

Operating System Support

The first Indigo 2 systems were introduced during the 4D1-4.x era. These were based on the R4000 microprocessor and featured Express graphics (Elan, XZ). Support for new hardware was added in future releases during this period and later on in the 4D1-5.x era.

Major milestones include the introduction of the Impact graphics options as well as the step from the R4000 to the R10000 CPU. For Impact graphics special versions of the IRIX 5.3 and IRIX 6.2 release were offered. Similarly a special release of IRIX 6.2 was made for the R10000 CPU upgrade.

General support for all Indigo 2 variants can be found in the all platform IRIX 6.5. The support for the remaining legacy systems like the Indigo 2 was dropped after 6.5.22 making IRIX 6.5.22 the last version to support any of these systems.