SGI Indigo
| Industry | Computer hardware |
|---|---|
| Founded | November 1, 1981 |
| Products | Workstation computers (including Indigo series) |
| Website | www |
The Indigo, initially launched as the IRIS Indigo, represents a series of workstation computers created and produced by Silicon Graphics, Inc. (SGI), with its debut announced in July 1991.
Renowned for its advanced graphics capabilities during its era, the Indigo excelled in hardware-accelerated 3D rendering. It came equipped with either a two-dimensional framebuffer or the Elan graphics subsystem, featuring between one and four Geometry Engines (GEs) specifically designed for 3D workloads. Additionally, SGI provided a server variant that omitted video hardware.
The system's design is characterized by a unique indigo-hued cubic case, expandable through the GIO32 bus interface.
Following the Indigo, SGI introduced the SGI Indigo2, while the SGI Indy took over the entry-level market segment.
Technical specifications
The initial Indigo model, codenamed Hollywood, was released on July 22, 1991. It utilized the IP12 processor board incorporating a fixed 32-bit MIPS R3000A CPU and proprietary memory slots that accommodated up to 96 MB of RAM.
In July 1992, the Blackjack iteration was introduced at a starting price of $, featuring a 64-bit MIPS R4000SC CPU running at 50 MHz. This version was built around the IP20 board and supported removable processor modules (PM1 or PM2) equipped with R4000 (100 MHz) or R4400 (100 or 150 MHz) CPUs compliant with the MIPS-III instruction set. Memory capacity expanded to a maximum of 384 MB via twelve standard 72-pin SIMM slots with parity support.
Audio input/output functions were managed by a Motorola 56000 DSP delivering four channels of 16-bit audio. Network connectivity relied on onboard Ethernet powered by the SEEQ 80C03 chipset integrated into the HPC (High-performance Peripheral Controller), which coordinated DMA transfers among the GIO bus, Ethernet, SCSI (WD33C93 chipset), and DSP components. The GIO bus interface was controlled by the PIC (Processor Interface Controller) on IP12 systems and by the MC (Memory Controller) on IP20 boards.
The Indigo’s hardware architecture is derived from the SGI IRIS 4D/3x series, sharing components such as memory controllers, Ethernet, SCSI interfaces, and optional DSP modules. The R3000-based Indigo serves as a cost-effective variant of the 4D/35 model but lacks VME bus support. While earlier models’ PIC supports VME expansion, it manages GIO slots on the Indigo. Across IP12, IP20, and subsequent systems like IP22/IP24 (SGI Indigo2), the HPC maintains connection to the GIO bus.
Entry graphics
The entry-level graphics option provides an 8-bit color framebuffer available in three configurations: one utilizing the system's GIO expansion bus, another integrated directly into the main backplane similar to XS, XZ, and Elan variants, and a version that includes an additional video output to enable dual-monitor setups.
XS Graphics
The XS Graphics option for Indigo incorporates a single GE7 Geometry Engine (GE), RE3 Raster engine, HQ2 Command engine, VC1, and XMAP5 components. Designed for cost-sensitive wireframe rendering rather than high-end textured graphics performance, four XS variants exist: XS-8 (offering 8-bit color with one VM2 video RAM module), XS-Z (adding a ZB-4 Z-buffer), XS-24 (equipped with two VM2 modules providing 24-bit color plus 32-bit brightness), and XS-24Z (which includes an additional Z-buffer).
XZ Graphics
As part of SGI’s Express series, the XZ graphics option closely resembles the XS-24Z configuration but enhances geometry processing by incorporating a second GE7 ASIC, effectively doubling its geometry engine capacity.
Elan Graphics
Elan represents the top-tier graphics solution for the Indigo, equipped with four GE7 Geometry Engine ASICs—doubling the geometry processing power compared to the XZ—delivering sophisticated rendering performance within SGI's Express series.
Operating system
The Indigo operates on IRIX, SGI's proprietary Unix-based operating system. Models based on the R3000 processor are compatible up to IRIX version 5.3, whereas those utilizing R4000 or R4400 processors support up to IRIX 6.5.22. Furthermore, the free Unix-like operating system NetBSD runs on IP12 and IP20 Indigo systems through the sgimips port.
Popular culture
In Jurassic Park, the Indigo was showcased as the graphics rendering machine used by Samuel L. Jackson’s character Arnold, working alongside a Macintosh Quadra 700 to manage the Park Control Systems visuals.