SGI Indigo Buyer's Guide

 General Information


The SGI Indigo is a very nice machine but maybe a bit too old and too slow for much serious work. It guess its mainly a collectors item and you still see some of them on ebay from time to time, but in most cases they get more expensive than an Indigo² or Indy which would offer more performance.

1. CPU and Mainboard

Basically there were two types of mainboards and three different CPUs:

Mainboard CPU Memory
IP12 (HP1) R3000A at 33MHz 8MB - 96MB proprietary modules
IP20 (HP2) R4000SC at 100MHz 8MB - 384MB PS/2 modules
IP20 (HP2) R4400SC at 150MHz 8MB - 384MB PS/2 modules

If you want to work with your Indigo, you really should get an IP20 Indigo with at least 100MHz. The 150MHz Indigos are rare, but you can also plug in a 150MHz CPU module of an Indy into the Indigo. The older IP12 based 33MHz Indigos aren't really fun any more for serious work!

2. Memory

As you can also see in the table above, older IP12-based Indigos need special RAM and offer only limited possibilities for RAM upgrades. The IP20 based Indigos need standard PS/2 FPM memory with parity - this shouldn't be a problem to find on second hand markets or ebay.

You should have at least 32MB of memory - as always more is better especially for newer IRIX releases. For IRIX 6.5 you really should have at least 128MB of memory.

3. IRIX Compatibility

Not all versions of IRIX run on the old IP12-based Indigo with the R3000 processor. The newest version that you can use is 5.3. And if you only have 32MB of memory or even less, you really should consider running IRIX 4.0.

On the other hand, the newer IP20-based Indigo will run IRIX up to version 6.5 - but you really should have at least 128MB of memory.

3. Graphics

Essentially there are two different graphics architectures available: The older 'Entry' graphics and the newer 'Express' graphics. The first one has only 8bits of colour and absolutely no hardware acceleration. But it comes with a standrd VGA connector instead of the 13W3 connectors. The express graphics architecture has many different possible variations with the best being the 'Elan' graphics card. Theoretically you can upgrade every express based graphics card up to Elan simply by adding a Z-Buffer module, memory-modules for the framebuffer and geometry engines - but don't count that you will find these anywhere on ebay.

This table lists most of the possible configurations of an express-styled graphics card. Again, the more framebuffer and geometry engines, the better it is.

Name Framebuffer Z-Buffer GEs
XS-8 1 module (8 bit colour) no 1
XS-24 3 modules (24 bit colour) no 1
XS-24Z 3 modules (24 bit colour) yes 1
XZ 3 modules (24 bit colour) yes 2
Elan 3 modules (24 bit colour) yes 4

You really should get an express based graphics card, as it is much faster than the old newport architecture.

Note that there is no option available for the Indigo with hardware accelerated textures - if you need these, you have to get an Indigo² or Octane with hardware texturing or an O2.

4. Disc Drives

One harddisc should be enough for your system. The size depends on the IRIX version you plan to install. Up to Version 5.3, a 1.2GB harddisc should be enough, for IRIX 6.5 you really should install at least a 2GB harddisc, better a 4GB harddisc.

5. Keyboard and Mouse

An annoying problem is that Indigos don't have PS/2 compatible keyobards and mice, although the connector looks like it. So when you want to buy an Indigo, you really should check that you also receive a keyboard and mouse, or you wonÄt have much fun with it, although it is possible to build a converter to plug in normal PS/2 styled keyboards and mice.

6. Other Details of Interest

There are some other items you should check before buying a specific Octane:

  • What is the general cosmetic condition?
  • Is the lockbar present? It prevents opening the case by unauthorized people.
  • Are keyboard and mouse included? Normal PS/2 styled keyboards and mice won't work!
  • Is IRIX installed, which version? Is it a clean install? Do you also get the installation CDs?
  • none