The Silicon Graphics Indigo2 was released in 1992/1993. Until the arrival of the Octane this was the company's top of the line workstation. Indigo2s came in 2 types, the original, teal colored ones and the later purple ones. The Indigo2s used Silicon Graphics' proprietary GIO-64 bus, and used SCSI-2 Narrow (50-pin) Single-Ended drives. (If you're looking for one of these on eBay you'll get really annoyed, cause most are either 68 or 80 pin ones). The company also used EISA slots in a hopeful attempt for 3rd party manufactures to work with, although little came out of the effort, but at least, with a few driver modifications, you can use the 3Com 3c597 ethernet card instead of a $100 Phobos one. Also, the RAM is used in sets of 4, there are 3 banks, and you must (I can't stress this enough) have a set of 4 (i.e. 4, 8, 12) or it will not work. These are standard 72-pin FPM true parity SIMMs and so no, sticking some of your old PC RAM will not work, it will do a nice startup tune though before failing to boot! I don't suggest buying these from Kingston or directly from any other licensed manufacturer. They cost upwards of $200 for a 128 MB set, and are a good $150 cheaper on eBay. I should also point out that there exists an rare and famous POWER Indigo2, with the R8000 processor. Dubbed as a "Cray on a desktop," it was only 75MHz for the Indigo2 (Only got up to 90MHz for Challenge and others), but was extremely awesome at doing floating point calculations as well as other things if programs were adjusted to this rather annoying to program chipset. The R10000 release sealed its doom. Lastly, I would like to point out that the Indigo2 isn't close to obsolete. Several Indigo2 Extremes were used in the making of Gladiator and there are still many graphics capablities of the system that a PC has yet to accomplish.

The Teal Colored Cases

These were the original Indigo2s released in 1992. They ran on either MIPS R4000 or R4400 processors with a maximum speed of 250MHz on the R4400s and had a 12 ram slots allowing up to 384MB of RAM. Also the 3 suppored graphics cards on the teal colored Indigo2s were: XL, XZ and Extreme Graphics. Below are the some details on each of the cards.

XL Graphics

This was the entry level card. Supported X and 2D graphics via hardware and could do 3D graphics using a software Z buffer.

XZ Graphics

XZ Graphics was the mid-range graphics card. It supported 3D graphics via hardware. Also, orignal XZ cards only had 2 Geometry Engines (GEs), later on SGI realized that many prefered 4 GEs so they upgraded them without out raising the price or name. Raised quite some confusion.

  • Command Engine - 80,000 gate device that delegates graphic primitives to the GEs.
  • 2/4 GE7 Geometry Engines. Two GEs gave 64 MFLOPS of graphics computation, 4 gave 128MFlops.
  • RE3 Raster Engine - 50MHz holds 100,000 custom gates.
  • Live Video I/O Slot

Extreme Graphics

At the time, it was the was the world's fastest desktop graphics system. It could do 630K triangles and 1.25 million 3D vectors per second.

  • Command Engine (Same as XZ Graphics)
  • 8 Geometry Engines - Provided 256 MFLOPS through a multi-chip module design.
  • 2 Integrated Raster Engines - Hold 200,000 custom gates at 50MHz.
  • Live Video I/O Slot

The Purple Colored Ones

About 2 or so years after the inital release of the Indigo2, Silicon Graphics released a new type of Indigo2, called IMPACT. These came in (obviously) purple cases, and had the new IMPACT graphics cards installed, they also supported the MIPS R8000 (Stated in early product guides, I have yet to see one) and R10000 CPUs and a maximum of 640MB of RAM. The IMPACT cards required a complete new power supply and backboard. So, to upgrade would be quite a hefty sum. The IMPACT graphics were the type also used on the new and much more expensive Octane systems. For the Indigo2, they came in Solid, Maximum, and High, I will go into a bit more depth below.


This the entry IMPACT card.

  • Command Engine - 300,000 gate device that delegates graphic primitives to the GEs.
  • GE8 Geometry Engine - Provided 960 MFlops through a multi-chip module design.
  • RE4 Raster Engine - Pixel-fill capablities; 600,000 gates.
  • Live Video I/O Slot
  • 2 PP1 Pixel Pipe Processors - Provided blending, depth and dithering; 290,000 gates each


Mid-level IMPACT card.

  • Exactly the same as Solid, except for Texture RAM (Interpolates image/texture data and performs MIP-mapping interpolation, 1 MB of texture memory with expandability to 4MB through optional Mezzanine card; 60,000 gates + 8Mb DRAM for each MB) and TE Texture Engine (Fill, warp, and zoom image/texture data; 295,000 gates each)
Maximum IMPACT

The fastest desktop graphics card at the time (circa. 1995)

  • Command Engine
  • 2 GE8 Geometry Engines
  • 2 TE Texture Engines
  • Live Video I/O Slot
  • 4 PP1 Pixel Pipe Processors
  • 2 RE4 Raster Engines

The MIPS Processors

The following processors were used in the Indigo2. All were 64-bit processors. However, only the R10000 used 64-bit pointers. Not really a big deal, since they're only useful if you start having gigabytes of RAM.

  • R4000
  • R4400 (175MHz, 200MHz, 250MHz)
  • R4600 (Rare! Came only in 133MHz for it)
  • R8000 (Rare! Only issued in 75MHZ and was the Power Indigo2)
  • R10000 (175MHz, 195MHz)

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