SGI Indigo

The Indigo entered production in 1991 and was discontinued in 1995. The Indigo was offered in both R3000 and R4000 based CPU configurations.

The SGI Indigo was a line of computer workstations manufactured by Silicon Graphics beginning in 1990. The initial Indigo (codename Hollywood) was based on the IP12 processor board, which contained a 32-bit MIPS R3000A RISC processor soldered on the board and proprietary memory slots. The later version (codename Blackjack) was based on the IP20 processor board, which had a removable processor module (PM1 or PM2) containing a 64-bit MIPS R4000 or R4400 processor. The IP20 used standard 72-pin DIMMs with parity.

The Indigo was designed to run SGI's version of UNIX, known as IRIX. The Indigos with R3000 processors were supported in IRIX through version 5.3 of that operating system, while Indigos equipped with a R4000 or R4400 processor can run IRIX 6.5. The machine in the hinv section below runs IRIX 4.0.5. Additionally, the free Unix-like operating system NetBSD has support for both the IP12 and IP20 Indigos as part of the sgimips port.

The Indigo was 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 or, for use as a 3d-graphics workstation, with the Elan graphics subsystem including one to four GEs (Geometry Engines).

A Motorola 56000 DSP was used for Audio IO. Ethernet is supported onboard by the SEEQ 80c03 chipset coupled with the HPC (High-performance Peripheral Controller), which provides the DMA engine. The HPC interfaces primarily between the GIObus and the ethernet, SCSI (wd33c93 chipset), and m56000 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 4D/3x series, which shares the same memory controller, Ethernet, SCSI, and optionally DSP as the IP12 Indigo. Indeed, 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 attaches to the GIO bus.

An SGI Indigo R4000

The Indigo was a visually pleasing design, based on a simple cube motif in indigo hue. Graphics and other peripheral expansion was 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), although Indigos remain useful among some specialties even into the 2000s.

The IRIS Indigo was one of the most powerful 3D machines on the market at the time. It was intended as a smaller desktop workstation replacement for the larger, heavier 4D series of workstations. The Indigo was known by the codename BlackJack while in development, and its original SGI model number was CMNB003. When it was introduced, SGI marketing created several working espressso machines that looked just like an Indigo called the Espressogo.

The Indigo gets its name from the dark blue color of its case and IRIS stands for "Integrated Raster Imaging System". It is 15" high, 9.5" wide, 10.9" deep, and weighs 25 lbs. On the front right is a door that hides the drive bays, a lock bar, and a reset button. The lock bar is a steel bar that goes through the entire system, and accepts a padlock to prevent anyone from opening the system. The back of the Indigo has power, SCSI, keyboard, serial, audio, video, genlock, ethernet, and parallel connectors, and a ventilation opening near the power supply.

The first Indigo has a 32-bit, 33Mhz MIPS R3000 RISC CPU with SGI 64-pin proprietary memory, keyboard, and mouse, and is cap able of addressing up to 96MB of memory. Notably, it is unable to use more than one bank of 4MB memory modules. The R3000 Indigo shipped with three graphics configurations: LG1 (aka, entry), XS, and XS-24. The last version of IRIX to run on the R3k Indigo was IRIX 5.3 w/XFS. SGI also produced Indigos for other companies, such as Colorbus Corp. These Indigos were standard stock, with custom company logos on the door. The HINV IP identifier for R3k CPUs is IP12.

In early 1992 SGI introduced the 64-bit, 100Mhz MIPS R4000 RISC Indigo. The R4000 uses standard 72-pin parity SIMMs for memory and addresses up to 384MB of memory. The R4000 shipped with five different graphics configurations: LG1, XS, XS-24, XZ, and ELAN. The R4000 Indigo is capable of running the latest versions of IRIX. The R4000 Indigo is also upgradeable to a R4400 150Mhz CPU found in older Indigo 2s. The R4000 is clock multiplied at 50Mhz, and the R4400 at 75Mhz. The HINV IP identifier for R4k CPUs is IP20.

The entry-level graphics are 8-bit, do not include any geometry engines, and are on the bottom of the performance scale. The entry board has two video connectors on it, an HD15 and a 13W3, and video output is locked a t 1024x768. SGI produced two entry-level graphics boards, the LG1 and the LG2. The only difference is the LG2 board is pale green with the "Song and Dance Machine" logo silk screened on it. XS, XS-24, and XZ graphics are the next option after entry-level graphic s and are in the mid-level price/performance range. XS is 8-bit color with one geometry engine (GE). The XS-24 is identical to the X S, but includes a Z-buffer, and is capable of 24-bit color. For increased 3D performance, SGI introduced the XZ, which is identical to the XS-24 but includes a second GE. The ELAN graphics option is the best for the Indigo -- it is the same as the XS-24, but with four GEs. Most Indigo R3k machines were marked with a graphics level logo on the door, and R4k Indigos had a graphics badge to identify which graphics option they had.

CPU types

The Silicon Graphics IRIS Indigo has been available with two completely different versions of CPU boards and a total of three different Mips RISC CPUs.

  CPU              clockspeed    CPU module     CPU board
  Mips R3000A      33 MHz        *----- HP1 -----*
  Mips R4000SC     50/100 MHz    PM1            HP2
  Mips R4400SC     75/150 MHz    PM2            HP2

In the rest of this document "Indigo" will be used if the type of CPU installed does not matter. "R3K Indigo" is the term used for Indigos based on R3000 processors and "R4K Indigo" will be used when machines using R4000 or R4400 processor are meant.

GFX options

There are two entirely different types of graphics options. One is called "Entry-Level-Graphics" or "Starter-Graphics" (LG1/LG2) and is a simple 8bit framebuffer. The second type is actually a complete family of graphics options built from the same components and is called "Express Graphics".

  name             color     z-buffer    GEs     connectors
  LG1              8bit      none        none    13W3, HD15
  LG2              8bit      none        none    13W3, HD15
  GR2-XS           8bit      none        1       13W3, BNC, minDIN
  GR2-XS24         24bit     none        1       13W3, BNC, minDIN
  GR2-XS24Z        24bit     yes         1       13W3, BNC, minDIN
  GR2-XZ           24bit     yes         2       13W3, BNC, minDIN
  GR2-Elan         24bit     yes         4       13W3, BNC, minDIN


All Indigos have/had markings that showed the configuration the machine was sold with. It is not recommended to rely on this information because parts may have been swapped or the machine could have been upgraded. R3K Indigos have the name of the graphics option printed on the drive door. Possible values are "Elan", "XZ", "XS24", "XS" and "Data Station".

On R4K Indigos plastic badges are used to denote the type of graphics option: "Elan 4000" (yellow), "XZ 4000" (green), "XS24 4000" (green), "XS 4000" (green), "Entry 4000" (red) and "Server 4000" (grey).

Again: Do *not* rely on the badge or the words on the drive door!

CPU Options

Indigo cpu baord.jpg
SGI Part Number Description
030-8096-004 HP2 R4000 Processor board
030-8044-00x HP1 R3000 Processor board
030-8118-001 HP1 R3000 Processor board
030-8097-002 PM1 100MHz R4000SC processor module w/1MB SC
030-8097-002 PM2 100MHz R4000 Processor module w/1MB SC
030-8116-004 PM2 150MHz R4400SC processor w/1MB SC

How to determine CPU type

When IRIX is running

Open a UNIX shell and run 'hinv'. Among other things the command shows the type of CPU that is installed in the machine.

The following is an indented and abbrevated output of 'hinv' on an R3K Indigo:

  1 33 MHZ IP12 Processor
  FPU: MIPS R2010A/R3010 VLSI Floating Point Chip Revision: 4.0
  CPU: MIPS R2000A/R3000 Processor Chip Revision: 3.0   
  Both of the following parts show an R4K Indigo:
  1 100 MHZ IP20 Processor
  FPU: MIPS R4000 Floating Point Coprocessor Revision: 0.0
  CPU: MIPS R4000 Processor Chip Revision: 2.2
  1 150 MHZ IP20 Processor
  FPU: MIPS R4000 Floating Point Coprocessor Revision: 0.0
  CPU: MIPS R4400 Processor Chip Revision: 5.0

From the PROM monitor

In the PROM monitor you can also use the 'hinv' command to determine the CPU that is installed in the Indigo. The output looks slightly different and there is a special issue with the R4K Indigo.

On an R3K 'hinv' shows as expected an IP12 System and an R3000 processor running at 33 Mhz. The following excerpts are again from an R4K Indigo (the same machines as the R4K Indigo examples from above).

                System: IP20
             Processor: R4000 50 Mhz, with FPU   
                System: IP20
             Processor: R4000 75 Mhz, with FPU

Note that the R4400 processor is not recognized in the PROM monitor. Additionally the 'hinv' command from the PROM shows always the external clockspeed of the system. The 'hinv' command in IRIX has later been changed to show the internal clockspeed.

When the machine does not boot

You can determine the type of Indigo just by looking at the CPU or the CPU board.

The R3000 processor on the R3K Indigo board is placed directly on the board itself. It carries *no* heatsink.

The processors on R4K Indigos is in a small module that is placed above the CPU board. The R4000 models carry a dark black/blue heatsink and the R4400 processors a huge heatsink that covers the whole module. The heatsink of both models is visible in the space between the CPU module and the case of the Indigo.

Additionally you can try to locate the part number of the boards. The one frome the R3K Indigo is called HP1 and the one from the R4K models HP2.

How to determine the GFX option

When IRIX is running

As usual you can use 'hinv' in the UNIX shell to determine the type of graphics option that is installed. The output lists the name of the graphics option as "Graphics board". The following list shows some example outputs (for further reference see further above this page):

  Graphics board: LG1
  Graphics board: GR2-XS24 with Z-buffer
  Graphics board: GR2-XZ
  Graphics board: GR2-Elan

Additionally you can use '/usr/gfx/gfxinfo' to get detailed information on the parts of the graphics subsystem.

From the PROM monitor

Again 'hinv' is the solution to determine the type of graphics option from the PROM monitor. The output is similar to the 'hinv' output shown above.

When the machine does not boot

The first thing to determine is if the board is an "Entry-Level" or "Express" graphics board (Confused? Read 1.2). This can be done without even opening the computer.

When you look on the back of the machine look for the femal 13W3 monitor connector (the one with 3 big and 10 small pins). If you find below that one just an HD15 VGA style connector the installed graphics option is "Entry-Level". If you see a BNC (Genlock) and a miniDIN (3D) connector than it is one of the "Express" graphics boards.

In case of an "Express" board the next step is determining the actual type. The table in 1.2 shows that the various versions differ in 3 aspects:

  1. color: 8bit vs. 24bit
  2. Z-buffer: hardware or none (calculations done in software)
  3. geometry engines: number of GEs

All "Express" boards are built of the following parts:

  • GR2: main graphics board
  • GE7: geometry engine (processor offering 32 MFlops)
  • VB1.1: video buffer board (includes RAMDAC)
  • ZB4: z-buffer board (includes z-buffer memory)
  • VM2: proprietary SIMM module (3 required for 24bit color)

Every "Express" board consist of 1 GR2, 1 VB1.1, at least 1 GE7 and 1 VM2.

The VB1.1 is a daughterboard that is placed on the left half of the GR2 board just above the VM2 SIMMs and the ZB4 daughterboard is placed on the right half. For the GE7 processors the GR2 board as 4 sockets at its center.

Knowing the variations of "Express" boards that exist (1.2) and the various parts and their functions it is easy to determine the type of an "Express" board.

Example: The board in question has an empty space on the right half (i.e. no ZB4), 3 VM2 modules and 1 GE7 (of course it has also 1 VB1.1 and 1 GR2). This boardset offers 24bit color, no hardware z-buffer and has 1 geometry engine. According to the table further up the page that makes it a GR2-XS24 graphics option.

Key Indigo Dates:

  • 1991, July: Indigo systems with R3000 processor announced. Read the official press release from 1991. indigo-announce.txt
  • 1992, January: XS and XS24 graphics options announced to ship in March, Elan to *ship in April
  • 1992, September: Indigo R4000 shipment announced for September 1992
  • 1993, January: XZ graphics options announced to ship in January

Can't set TOD problem

A new battery cost $12 (AUD) from Farnell, as of 18th of November, 2009.

Desoldering and resoldering took about 5 minutes.

Farnell had them in stock in the USA and took about 2 weeks to deliver to Australia.

Changing the battery

Signs of battery failure

When the onboard battery of the Indigo fails while the machine is running nothing happens until the next time the machine is shut down and then switched on again.

When the battery is empty the Indigo refuses to boot. It constantly repeats the following error message:

Initializing tod clock.
setting secs=0 min=0 hour=0 day=1 month=1 year=0
Can't set tod clock.

Effects of battery failure

The Indigo does not boot until it has a new battery. After that the date/time is wrong but aside from that nothing really bad happens (usually). Other systems as for example old Sun Sparcstations (IPC or IPX) forget important data like the ethernet MAC adress when the battery in their NVRAM fails.

What to do

The solution to the battery problems is the same as on a cheap flashlight: Replace the old battery with a new one. Sounds easy but it is slightliy more difficult.

On both types of Indigos (R3K and R4K - see Indigo Versions FAQ for details) the battery is located on the CPU board. In the R3K Indigo it is put in a "socket", in the R4K models it is soldered in place.

Before you start

Before describing the procedure in detail it is time to adress the reader (especially the ones who have to work on an R4K Indigo).

Begin your work only if you know what you are doing and you have the right tools at hand. If you are not sure or have no experience at all in working on electronic equipment please ask someone experienced to help you. Although the procedure is not that difficult there is a chance to do real damage to the computer.

The descriptions won't mention how to take the parts out of the Indigo and how they are placed back in. There are good descriptions in the Indigo Owners guide for that. Read the appropriate sections carefully!

Obtaining the Battery

The battery type used in the Indigo R4000 systems is a Tadiran TL-5186 (the one on R3000 systems looks the same and maybe is as well a TL-5186). A battery with the same dimensions and technical data is a Sonnenschein SL-340 which might be easier to obtain in some places (Austria, Germany, Netherlands and maybe Europe in general).

On Indigo R3K Systems

Changing the battery on R3K systems is pretty simple. The battery is on the right side of the board close to its edge hidden below the dummy that can be replaced with a GIO card. After removing the dummy the old battery can be taken out of its "socket" and be replaced by a new one. The "socket" is actually only a small rubber strap that holds the battery in place.

Attention! Make sure that you do NOT insert the battery the wrong way. This may cause damage to the mainboard and leave you with a dead system.

On Indigo R4K Systems

The situation on R4K Indigos is a bit more complicated. The battery is located on the CPU board right below the CPU module but it is soldered in place. It is not too difficult to find the pins from the battery on the back of the board.

The procedure itself is pretty obvious and not too difficult with the right tools and a second person that helps holding the board and pulls on the battery while the first works with the desoldering tools and pays attention that no parts get damaged, burned or whatever bad can happen. Clean the soldering points after the battery has been removed and solder the new one in place.

Attention! Make sure that you do NOT insert the battery the wrong way. This may cause damage to the mainboard and leave you with a dead system.

When finished

When booting the Indigo for the first time after replacing the battery enter maintenance mode and go into the PROM monitor. Set the clock and boot the machine. Everything should work fine now.

Example hinv

hinv -v
1 33 MHZ IP12 Processor
FPU: MIPS R2010A/R3010 VLSI Floating Point Chip Revision: 4.0
CPU: MIPS R2000A/R3000 Processor Chip Revision: 3.0
On-board serial ports: 2
Data cache size: 32 Kbytes
Instruction cache size: 32 Kbytes
Main memory size: 64 Mbytes
Integral Ethernet: ec0, version 0
Disk drive: unit 1 on SCSI controller 0
Integral SCSI controller 0: Version WD33C93B, revision C
Iris Audio Processor: revision 10
Graphics board: LG1

Graphics board 0 is "LG1" graphics.
        Managed (":0.0") 1024x768 
        LG2 revision 3, REX revision 1.5, VC1 revision B, PIC rev 1.5
        14" monitor, video option not installed.


Physical Environment

System 15 inches H x 9.5 inches W x 10.9 inches D 24 lbs.
16-Inch Monitor 16.1 inches H x 16.0 inches W x 18.8 inches D 52.9 lbs
19-Inch Monitor 18.7 inches H x 18.9 inches W x 19.9 inches D 71.6 lbs
Power Requirements Voltage and Frequency
 100-240 VAC
 2.7 - 1.8A 47-63 Hz
 120 V 2.5A (without monitor)
 120 V 2.5A (with monitor)
Heat Dissipation 1200 BTU/hour
Ambient Temperature +13 to +35 degrees C operating
 -40 to +65 degrees C non-operating
Noise 36 dB (A) in typical operating position
Relative Humidity 10% to 80% operating no condensation
 10% to 95% non-operating no condensation
Altitude 10,000 feet operating
 40,000 feet non-operating
Vibration 0.02 inches, 5-19 Hz
 0.35 G, 19-500 Hz


Controller/Processor Motorola 56001 DSP 0 20 MHz
Input/Output Stereo line-level analog
 Mono microphone
 Serial digital (stereo), lEC958
 Stereo headphone
 Internal mono speaker
Sampling Rates 48, 44.1, 32 KHz, and many lower rates
Converters Analog to digital conversion
 (16 bit stereo, 64 I/C oversampling)
 Digital to analog conversion
 (stereo 16/18 bit stereo, 8x oversampling
 with digital filter)
Connectors 5 stereo mini-phone jacks, 1/8 inch (3.5 mm)
Video Video slot on graphics board
 Independent video bus
 Genlock (XS, XS24, XZ, Elan)

SGI Part Numbers

Part Number Description
030-8050-002 Indigo Backplane. (VME Connectors for CPU board, and SCSI connectors for drives.)
030-8058-006 Main Graphics Board with 4 GE-7's (ELAN)
030-8060-001 Z-Buffer Board
030-8093-002 Video Buffer Board
030-8059-002 Video Memory Board
030-8044-003 33MHz R3000 INDIGO CPU Board
034-8077-004 LG1 8Bit Graphics Board
030-8077-003 LG2 8 Bit Graphics Board
050-8000-001 INDIGO Drive Sled
030-8042-002 INDIGO R3000 2MB Memory Modules
030-8054-002 INDIGO R3000 4MB Memory Modules
030-8072-002 INDIGO R3000 8MB Memory Modules
030-7005-002 INDIGO GIO-BUS AUI Ethernet card
030-0246-006 Single-Ended FDDI, GIO-BUS
9430810 R3000 INDIGO Power Supply
9430812 R4000/R4400 INDIGO Power Supply
HP2/PM2 INDIGO R4400-150 CPU
HP2/PM1 INDIGO R4000-100 CPU
HP1 INDIGO R3000 CPU Board
030-8122-001 GR2-2 Graphics Board with 2 GE-7's (XZ)
030-8058-007 GR2-1 Graphics Board with 1 GE-7 (XS,XS24)
030-8095-0003 INDIGO-VIDEO, Real Time Video Board
030-8113-001 Video Buffer
9500801 INDIGO Keyboard
9150800 INDIGO Mechanical Mouse
050-8004-001 Plastic INDIGO Skins
050-8010-001 Plastic INDIGO Front Cover
050-8027-001 Plastic INDIGO Drive Cover
P5-T4C3A 150MB 1/4" External SCSI Tape Drive
P3-T13D 4mm. SCSI DAT Drive

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