SGI Indigo²

Indigo2 IMPACT R10000
Manufacturer	Silicon Graphics, Inc.
Release date	1992 (1992)
Discontinued	1997 (1997)
Operating system	IRIX
CPU	MIPS architecture
Website	sgi.com

The SGI Indigo2 (stylized as "Indigo²") and the SGI Challenge M are Unix workstations which were designed and sold by SGI from 1992 to 1997.

The Indigo2, code named "Fullhouse", is a desktop workstation. The Challenge M is a server which differs from the Indigo2 only by a slightly differently colored and badged case, and the absence of graphics and sound hardware. Both systems are based on the MIPS processors, with EISA bus and SGI proprietary GIO64 expansion bus via a riser card.

The SGI Indigo is succeeded by Indigo2, which is succeeded by SGI Octane.

Indigo2 desktop workstations have two models: the teal Indigo2 and the purple IMPACT model. Both have identical looking cases except color, and sub-model case badging. The available CPU types, the amount of RAM, and graphics capabilities, depend on the model or sub-model variation. There is a special version of the teal Indigo2, called Power Indigo2, with increased FPU (floating point unit) capabilities and specially designed R8000 CPUs. The later IMPACT Indigo2 workstation model gives more computational and visualization power, especially due to the introduction of R10000 series RISC CPU, and IMPACT graphics.

All Indigo2 models use one of four distinct MIPS microprocessor variants: the 100 to 250 MHz MIPS R4000 and R4400, and the Quantum Effect Devices R4600 (IP22 mainboard); the 75 MHz MIPS R8000 (IP26 mainboard); and the 175 to 195 MHz R10000 (IP28 mainboard), which are featured in the last produced Indigo² model, the "IMPACT10000". Each microprocessor family differs in clock frequency, primary and secondary cache capacity.