The Indigo, introduced as the IRIS Indigo, is a line of

workstation A workstation is a special computer designed for technical or scientific applications. Intended primarily to be used by a single user, they are commonly connected to a local area network and run multi-user operating systems. The term ''worksta ...

computers developed and manufactured by Silicon Graphics, Inc. (SGI). SGI first announced the system in July 1991. The Indigo is considered one of the most capable graphics workstations of its era, and was essentially peerless in the realm of hardware-accelerated three-dimensional graphics rendering. For use as a graphics workstation, the Indigo was equipped with a two-dimensional

framebuffer A framebuffer (frame buffer, or sometimes framestore) is a portion of random-access memory (RAM) containing a bitmap that drives a video display. It is a memory buffer containing data representing all the pixels in a complete video frame. Moder ...

or, for use as a 3D graphics workstation, with the

Elan graphics Elan Graphics is a computer graphics architecture for Silicon Graphics computer workstations. Elan Graphics was developed in 1991 and was available as a high-end graphics option on workstations released during the mid-1990s as part of the Expr ...

subsystem including one to four

Geometry Engine Geometric manipulation of modelling primitives, such as that performed by a geometry pipeline, is the first stage in computer graphics systems which perform image generation based on geometric models. While geometry pipelines were originally implem ...

s (GEs). SGI sold a server version with no video adapter. The Indigo's design is based on a simple cube motif in

indigo Indigo is a deep color close to the color wheel blue (a primary color in the RGB color space), as well as to some variants of ultramarine, based on the ancient dye of the same name. The word "indigo" comes from the Latin word ''indicum'', ...

hue. Graphics and other peripheral expansions are accomplished via the GIO32 expansion bus. The Indigo was superseded generally by the SGI Indigo2, and in the low-cost market segment by the

SGI Indy The Indy, code-named "Guinness", is a low-end multimedia workstation introduced on July 12, 1993. Silicon Graphics Incorporated (SGI) developed, manufactured, and marketed Indy as the lowest end of its product line, for computer-aided design ( ...

Technical specifications

The first Indigo model (code-named ''Hollywood'') was introduced on July 22, 1991. It is based on the IP12 processor board, which contains a 32-bit MIPS R3000A microprocessor soldered on the board and proprietary memory slots supporting up to 96 MB of RAM. The later version (code-named ''Blackjack'') is based on the IP20 processor board, which has a removable processor module (PM1 or PM2) containing a 64-bit MIPS

R4000 The R4000 is a microprocessor developed by MIPS Computer Systems that implements the MIPS III instruction set architecture (ISA). Officially announced on 1 October 1991, it was one of the first 64-bit microprocessors and the first MIPS III implem ...

(100 MHz) or R4400 processor (100 MHz or 150 MHz) that implements the MIPS-III instruction set. The IP20 uses standard 72-pin SIMMs with parity, and has 12 SIMM slots for a total of 384 MB of RAM at maximum. A Motorola 56000 DSP is used for Audio IO, giving it 4-channel 16-bit audio.

Ethernet Ethernet () is a family of wired computer networking technologies commonly used in local area networks (LAN), metropolitan area networks (MAN) and wide area networks (WAN). It was commercially introduced in 1980 and first standardized in ...

is supported on board by the SEEQ 80C03 chipset coupled with the HPC (High-performance Peripheral Controller), which provides the

DMA DMA may refer to: Arts * ''DMA'' (magazine), a defunct dance music magazine * Dallas Museum of Art, an art museum in Texas, US * Danish Music Awards, an award show held in Denmark * BT Digital Music Awards, an annual event in the UK * Doctor of M ...

engine. The HPC interfaces primarily between the GIO bus and the Ethernet,

SCSI Small Computer System Interface (SCSI, ) is a set of standards for physically connecting and transferring data between computers and peripheral devices. The SCSI standards define commands, protocols, electrical, optical and logical interface ...

(WD33C93 chipset) and the 56000 DSP. The GIO bus interface is implemented by the PIC (Processor Interface Controller) on IP12 and MC (Memory Controller) on IP20. Much of the hardware design can be traced back to the

SGI IRIS 4D The SGI IRIS series of terminals and workstations from Silicon Graphics was produced in the 1980s and 1990s. IRIS is an acronym for Integrated Raster Imaging System. Overview 68000 The early systems up to IRIS 3000 use the Motorola 68000 series ...

/3x series, which shared the same

memory controller The memory controller is a digital circuit that manages the flow of data going to and from the computer's main memory. A memory controller can be a separate chip or integrated into another chip, such as being placed on the same die or as an in ...

, and optionally DSP as the IP12 Indigo. The 4D/30, 4D/35 and Indigo R3000 are all considered IP12 machines and run the same IRIX kernel. The Indigo R3000 is effectively a reduced cost 4D/35 without a VME bus. The PIC supports a VME expansion bus (used on the 4D/3x series) and GIO expansion slots (used on the Indigo). In all IP12, IP20, and IP22/IP24 (see SGI Indigo2) systems the HPC attached to the GIO bus.

Graphics options

Entry graphics

For entry graphics, the 8-bit color frame buffer comes in three versions. One version uses the system's GIO expansion bus. Another uses the main backplane like the XS, XZ, and Elan graphics options. The final is the same, but adds a second video output, giving the computer the ability to have two "heads", or monitors.

XS Graphics

The Indigo's XS Graphics option has a single GE7 Geometry Engine (GE), a RE3 Raster engine, a HQ2 Command engine, VC1, XMAP5. It is ideal for low-cost wireframe operations, compared to more powerful, and expensive options for textured graphics. Part of SGI's Express line of graphics, four XS graphics options were produced for the Indigo: the XS-8 offers 8-bit color, with one VM2 video RAM module; the XS-Z adds the ZB-4 Z buffer; the XS-24 adds two VM2 modules and offers 24 color bits and 32 bits including brightness; and the XS-24Z adds a Z buffer.

XZ Graphics

The XZ graphics option is also a member of SGI's Express graphics line. It is similar to the XS-24z, but it includes a second GE7 Geometry Engine ASIC, doubling its geometry performance.

Elan Graphics

The highest performance graphics option offered for the Indigo, it is a member of SGI's Express graphics line. It is like the XS-24z and XZ, but has 4 GE7 Geometry Engine ASICs, giving it twice the performance of the XZ option.

Operating system

The Indigo was designed to run

IRIX IRIX ( ) is a discontinued operating system developed by Silicon Graphics (SGI) to run on the company's proprietary MIPS workstations and servers. It is based on UNIX System V with BSD extensions. In IRIX, SGI originated the XFS file system ...

, SGI's version of

Unix Unix (; trademarked as UNIX) is a family of multitasking, multiuser computer operating systems that derive from the original AT&T Unix, whose development started in 1969 at the Bell Labs research center by Ken Thompson, Dennis Ritchie, a ...

. The Indigos with R3000 processors are supported up to IRIX version 5.3, and Indigo equipped with an R4000 or R4400 processor can run up to IRIX 6.5.22. Additionally, the free

Unix-like A Unix-like (sometimes referred to as UN*X or *nix) operating system is one that behaves in a manner similar to a Unix system, although not necessarily conforming to or being certified to any version of the Single UNIX Specification. A Unix-li ...

operating system

NetBSD NetBSD is a free and open-source Unix operating system based on the Berkeley Software Distribution (BSD). It was the first open-source BSD descendant officially released after 386BSD was forked. It continues to be actively developed and is a ...

has support for both the IP12 and IP20 Indigos as part of the sgimips port.

References

External links

IP12 - LinuxMIPS

Technolust: The Indigo Page (Silicon Graphics - SGI)

SGI Indigo / Silicon Graphics R4000 Architecture

Indigo Power Supply basics
{{Authority control

Indigo Indigo is a deep color close to the color wheel blue (a primary color in the RGB color space), as well as to some variants of ultramarine, based on the ancient dye of the same name. The word "indigo" comes from the Latin word ''indicum'', ...

32-bit computers 64-bit computers