SGI Indigo² and Challenge M

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An SGI Indigo² IMPACT R10000

The SGI Indigo² and the SGI Challenge M were Unix computers marketed by SGI from 1992 to 1997. The Indigo², code named Fullhouse, was a desktop workstation. The Challenge M was a server which differed from the Indigo² only by a slightly differently colored and badged case, and the absence of graphics and sound hardware. Both systems were based on the MIPS processors. Both systems supported EISA bus and SGI proprietary GIO64 expansion bus via a riser card. SGI Indigo² workstation is a direct successor to the famous SGI Indigo model. Until the introduction of SGI Octane, SGI Indigo² was SGI's most powerful desktop solution for 3D, visualization and high performance computing environments.

1 Introduction
2 CPU
3 Memory (RAM)
4 Graphics
5 External links

[edit] Introduction

There are two types of SGI Indigo² desktop workstations: the teal case Indigo² - earlier model (original concept), and the later - often called IMPACT model - with purple colored case. Both Indigo² cases from outside look the same (except color, and sub-model case badging). The available CPU types, the amount of RAM and GFX capabilites depends on the model or sub-model variation. There was a special version of the "Teal" Indigo², called Power Indigo²; this system had increased FPU (floating point unit) capabilities and used specially designed R8000 CPUs. It's natural that later IMPACT Indigo² workstation model gives more computational and visualization power, especially due to the introduction of R10000 series RISC CPU, and IMPACT graphics.

[edit] CPU

All Indigo² models use one of three distinct MIPS CPU variants: the 100-250MHz MIPS R4x00 family (R4000, R4400, R4600 CPUs), the 75MHz MIPS R8000 CPU, and the 175-195MHz R10000 CPUs, which are the core of the last produced Indigo² model, the "IMPACT10000". Each CPU family/model differs in CPU speed, L1+L2 (primary and secondary) data cache and the type of supported mainboards (IP22, IP26 and IP28).

[edit] Memory (RAM)

All SGI Indigo² models have 12 SIMM slots on the motherboard. The Indigo² uses standard 36-bit parity 72-pin fast page mode SIMM memory. The memory modules are seated in groups of four. Indigo² could be expanded to a thermal specification maximum of either 384 MB or 512 MB RAM. The design of the memory control logic in R10000 machines supported up to 1 GB RAM, but the thermal output of older generation of DRAM chips necessitated the 512 MB limit. With newer, higher-density and smaller scale modules, 768 MB was easily within heat output specifications. Later, 128 MB modules allowed the full 1 GB with eight out of twelve sockets occupied.

[edit] Graphics

The graphics options available for the SGI Indigo² can be divided in two groups: the "pre-IMPACT" and the "MGRAS IMPACT" boards.

"Pre-IMPACT" options consisted of the following options: SGI XL24, SGI XZ, SGI Elan and SGI Extreme). These options are based on the same "Express Graphics" architecture from the original SGI Indigo, but feature improved performance.

The "MGRAS IMPACT" boards include the Solid IMPACT, High IMPACT, High IMPACT AA, and the Maximum IMPACT, and are also known as the IMPACT graphics family. These newer boards have a different architecture to the earlier designs. Physically, they appear to be similar to the older graphics options - the low-end Solid IMPACT board takes up a single GIO-64 slot, the mid-range High IMPACT takes up two GIO-64 slots, and the high end Maximum IMPACT takes up to three. The High IMPACT and Solid IMPACT boards provides the same performance for non-textured tasks, while the Maximum IMPACT provides double the performance. The High IMPACT AA option is the same as the High IMPACT, except that it has the geometry performance of a Maximum IMPACT, but with the same the same pixel fill performance.

The IMPACT graphics was the first desktop graphics system from SGI to offer texture mapping acceleration, though only the High IMPACT and Maximum IMPACT had this capability, and came with 1 MB of texture memory as standard. The Solid IMPACT card is named "Solid" due to its applications for solid (non-textured) modeling. When expanded by adding a TRAM (Texture RAM) module to the board, the amount of texture memory can be increased to 4 MB. Maximum IMPACT graphics require two of these modules due its two pixel units, although this does not upgrade them to 8 MB, with the two modules merely working in parallel to render twice as fast. At the time of its release, Maximum IMPACT graphics was the world's fastest available top-end desktop visualization solution. A Maximum IMPACT with 4 MB of texture memory and the correct graphics settings can play id Software's Quake 1, 2 or 3 with acceptable frame rates.

It is possible to have a dual-head Indigo2 by merely adding another Solid IMPACT card. Valid configurations include Solid/Solid, Solid/High, Solid/Maximum. Although there are four GIO-64 slots available and the High IMPACT takes up two, it is not possible to have a High/High configuration.

The IMPACT boards draw more power than the GIO-64 bus can deliver, so IMPACT-ready systems have additional power connectors on the expansion riser card, with a separate connection to the power supply. An IMPACT-ready Indigo² must have an IMPACT-ready riser card, an IMPACT-ready power supply, and a sufficiently recent PROM revision. The Indigo2's replacement, the SGI Octane, offered an upgraded XIO bus but featured the same graphics options, albeit in repackaged form.