SGI Indigo² and Challenge M
| Company type | Product line |
|---|---|
| Industry | Computer workstations |
| Predecessor | SGI Indigo |
| Founded | 1992 |
| Defunct | 1997 |
| Successor | SGI Octane |
Area served | Worldwide |
| Products | Unix workstations (Indigo2, Challenge M) |
| Owner | Silicon Graphics, Inc. (SGI) |
The SGI Indigo2 (often written as "Indigo2") and the SGI Challenge M represent Unix workstation platforms developed and marketed by SGI between 1992 and 1997.
The Indigo2, internally known as "Fullhouse," is a desktop-oriented workstation, whereas the Challenge M is a server distinguished primarily by its exterior color, branding, and the lack of integrated graphics and audio components. Both systems are powered by MIPS CPUs and incorporate an EISA bus alongside SGI’s proprietary GIO64 expansion interface via a riser card.
The original Indigo was succeeded by the Indigo2, which in turn was replaced by the Octane.
Overview
Indigo2 workstations are available in two main variants: the teal-colored Indigo2 and the purple-hued IMPACT model. Apart from differences in color and branding, their chassis are largely identical. Variations between models include CPU type, memory capacity, and graphics capabilities. The Power Indigo2, characterized by its teal casing, incorporates the R8000 chipset known for robust floating-point arithmetic performance. The subsequent IMPACT version introduced superior processing power and visualization features, leveraging the R10000 series RISC processors alongside advanced IMPACT graphics technology.
CPU
Indigo2 systems utilize one of four MIPS CPU options: 100 to 250 MHz MIPS R4000/R4400 or Quantum Effect Devices R4600 on the IP22 mainboard; 75 MHz MIPS R8000 on the IP26 mainboard; or 175 to 195 MHz R10000 on the IP28 mainboard, as seen in the final IMPACT10000 release. Each CPU variant differs in operating frequency and cache size.
RAM
Every Indigo2 motherboard accommodates twelve SIMM slots designed for 36-bit parity 72-pin fast page mode SIMMs, installed in sets of four. Memory support extends up to 384 MB or 512 MB due to thermal constraints associated with older DRAM chips; however, the R10000 memory controller can address up to 1 GB. Utilizing newer high-density modules allows configurations up to 768 MB within thermal limits, while later 128 MB modules enable reaching the full 1 GB capacity using eight out of twelve available slots.
Storage
The Indigo2 supports two front-accessible 3.5" SCSI hard drives and one 5.25" SCSI CD-ROM drive housed in bays equipped with proprietary sleds. Its internal SCSI bus operates at approximately 10 MB/s, commonly paired with narrow (SCSI-1) drives spinning at either 5200 rpm or 7200 rpm. Although all sleds feature a standard 50-pin female SCSI-1 connector and power supply interface, higher-performance U160 and U320 SCSI drives can be integrated using suitable adapters.
Networking
A built-in 10 Mbit Ethernet LAN interface is standard on Indigo2 systems, with third-party expansions available for 100 Mbit connectivity via EISA or GIO64 cards. The most frequently used network adapters include the 3Com 3C597-TX (100 Mbit EISA) and the Phobos G160 GIO64 card—the latter providing enhanced throughput and lower CPU overhead through DMA-based data transfers.
Graphics
Indigo2 graphics solutions fall into two main groups: pre-IMPACT boards and the MGRAS IMPACT series.
Pre-IMPACT options encompass Indigo2 XL24, Indigo2 XZ, Elan, and Extreme Graphics—all derived from the Express Graphics architecture originally developed for the SGI Indigo but with improved capabilities. The Indigo2 XZ debuted in August 1993 at a price point of US$25,500; shortly thereafter, the Indigo2 XL was introduced in Q3 of that year priced at US$18,000.
The MGRAS IMPACT lineup—comprising Solid IMPACT, High IMPACT, High IMPACT AA, and Maximum IMPACT—employs a distinct architectural design. Solid IMPACT occupies one GIO-64 slot; High IMPACT requires two slots; Maximum IMPACT spans three slots. While Solid and High IMPACT deliver comparable performance on non-textured rendering tasks, Maximum IMPACT offers roughly double that capability. High IMPACT AA matches Maximum IMPACT’s geometry processing speeds but maintains pixel fill rates equivalent to High IMPACT.
IMPACT graphics were pioneering in providing desktop texture mapping acceleration—available exclusively on High and Maximum IMPACT boards—with a baseline of 1 MB texture memory expandable to 4 MB through TRAM modules. Maximum IMPACT mandates two TRAM modules operating concurrently for enhanced rendering speed but does not increase total texture memory beyond 4 MB. At launch, Maximum IMPACT represented the fastest desktop visualization hardware worldwide; it was capable of running early Quake titles at playable frame rates when equipped with sufficient texture memory.
All Indigo2 graphics adapters utilize standard 13W3 connectors for monitors along with additional ports for stereoscopic 3D glasses.
Dual-display setups are achievable by installing a second Solid IMPACT board, enabling combinations such as Solid/Solid, Solid/High, or Solid/Maximum configurations. However, pairing two High IMPACT cards is unsupported due to slot limitations.
Because IMPACT graphics require more power than standard GIO-64 specifications allow, these systems must use an IMPACT-compatible riser card featuring extra power connectors along with an appropriate power supply unit and PROM firmware revision. The succeeding SGI Octane platform introduced an upgraded XIO bus architecture alongside repackaged versions of these graphics technologies.