SGI Indigo2 and Challenge M

The SGI Indigo2 and the SGI Challenge M were UNIX machines marketed by SGI from 1993 to 1997. The Indigo2 was a desktop workstation. The Challenge M was a server which differed from the Indigo2 only by the absence of graphics hardware. Indigo2 and Challenge M systems used either the SGI IP22, SGI IP26 or SGI IP28 motherboards. The SGI IP22 supported MIPS R4000, MIPS R4400 or MIPS R4600 processor modules, and the SGI IP26 and SGI IP28 supported MIPS R8000 and MIPS R10000 processor modules, respectively. All of these motherboards had 12 72-pin SIMM slots, which accept 70 ns or faster parity SIMMs. These slots are in three banks of four SIMMs, so each bank is 128 bits wide. The IP22 board accepted SIMMs up to 32 MB, for a maximum of 384 MB of memory. The IP26 and IP28 boards accept 64 MB SIMMs, but the maximum memory is officially listed as 640 MB, due to overheating problems in 768 MB configurations with early 64 MB SIMMs. With more recent SIMMs these boards can accept 768 MB without any problems. The IP28 board is also known to accept 128 MB SIMMs, but can only address the first two banks in this configuration, giving a maximum of 1 GB.

The following processor modules were available for the Indigo2 and Challenge M (in order of increasing performance):

• For the IP22 motherboard:
  • R4000PC/100 (100 MHz MIPS R4000, 8 kB I-cache, 8 kB D-cache, no L2 cache)
  • R4000SC/100 (100 MHz MIPS R4000, 8 kB I-cache, 8 kB D-cache, 1 MB L2 cache)
  • R4600SC/133 (133 MHz MIPS R4600, 16 kB I-cache, 16 kB D-cache, 512 kB L2 cache)
  • R4400SC/100 (100 MHz MIPS R4400, 16 kB I-cache, 16 kB D-cache, 1 MB L2 cache)
  • R4400SC/150 (150 MHz MIPS R4400, 16 kB I-cache, 16 kB D-cache, 1 MB L2 cache)
  • R4400SC/175 (175 MHz MIPS R4400, 16 kB I-cache, 16 kB D-cache, 1 MB L2 cache)
  • R4400SC/200 (200 MHz MIPS R4400, 16 kB I-cache, 16 kB D-cache, 1 MB or 2 MB L2 cache)
  • R4400SC/250 (250 MHz MIPS R4400, 16 kB I-cache, 16 kB D-cache, 2 MB L2 cache)
• For the IP26 motherboard:
  • R8000SC/75 (75 MHz MIPS R8000, 16 kB I-cache, 16 kB D-cache, 2 MB L2 cache)
• For the IP28 motherboard:
  • R10000SC/175 (175 MHz MIPS R10000, 32 kB I-cache, 32 kB D-cache, 1 MB L2 cache)
  • R10000SC/195 (195 MHz MIPS R10000, 32 kB I-cache, 32 kB D-cache, 1 MB L2 cache)

All three of these motherboards supported EISA and GIO-64 expansion buses via a riser card. Early model riser cards had 3 physical GIO-64 slots and 4 EISA slots. Later riser cards had 4 physical GIO-64 slots, 3 EISA slots and 4 power connectors for SGI IMPACT graphics boards. In any case only two GIO-64 devices could be installed at one time, except for pairs of devices specially designed to share an interrupt, such as the IMPACT Compression and IMPACT Video boards. The multiplicity of physical slots exists to allow maximum flexibility with devices that filled multiple slots, such as the High IMPACT and Maximum IMPACT graphics boards.

Besides the three types of motherboards, another major factor dividing Indigo2 systems is support for SGI IMPACT graphics hardware. The IMPACT graphics boards draw more power than the GIO-64 bus can deliver, so the 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 graphics boards available for the Indigo2 were the pre-IMPACT boards, the SGI XL24, SGI XZ, SGI Elan and SGI Extreme, and the IMPACT boards, the SGI Solid IMPACT, the SGI High IMPACT and the SGI Maximum IMPACT. The XL24 was a 2D-only board, but it had a relatively high pixel fill rate and for some 2D tasks could perform as well as the much later High IMPACT board. The XL24 used one physical GIO-64 slot. The XZ, Elan and Extreme boards were built from differing numbers of the same GE (Geometry Engine) and RE (Raster Engine) chips. The XZ had two GEs and one RE, the Elan had four GEs and one RE, and the Extreme had eight GEs and two REs. The XZ and Elan boards took two physical GIO-64 slots, and the Extreme board took three slots. All of the pre-IMPACT 3D boards had a hardware Z-buffer, and none had hardware texture mapping.

The IMPACT boards were built around a later generation of higher-performance GEs and REs. The Solid IMPACT had one GE and one RE, and took up one physical GIO-64 slot. The High IMPACT had one GE and one RE as well, but added 1 MB of texture memory, and took two slots. For non-texture mapped graphics the Solid IMPACT and High IMPACT had equal performance. The Maximum IMPACT had 2 GEs, 2 REs and 1 MB of texture memory, offering roughly double the performance of the High IMPACT. The Maximum IMPACT took three slots. Both the High IMPACT and the Maximum IMPACT could be upgraded with TRAM modules, to 4 MB of texture memory. The Maximum IMPACT board kept two independent copies of the contents of texture memory, so that the two REs would not be competing for memory bandwidth, so upgrading a Maximum IMPACT board required two TRAM modules. There was also the so-called 'High-AA' variant of the High IMPACT. This was sold as a High IMPACT, but it had two GEs, so for some tasks, such as antialiasing, it had the performance of a Maximum IMPACT. It took up two slots and could be upgraded with one TRAM module.

Additional expansion boards available for the Indigo2 and Challenge M included:

• For pre-IMPACT systems:
  • The Indigo2Video board: (digital video I/O and display, no hardware compression, IndyCam support)
  • The Cosmo Compress board: (hardware compression, I/O via connection to Indigo2Video board)
  • The Galileo Video board: (digital and analog video I/O and display, no hardware compression)
• For post-IMPACT systems:
  • The Indigo2 Video for IMPACT board: Identical functionality to Indigo2Video, but designed to connect to IMPACT graphics boards.
  • The IMPACT Compression board: analog video I/O and two channels of real-time JPEG compression. This board is extremely rare and is one of the most sought-after pieces of Indigo2 hardware on the secondhand market. The IMPACT Compression board performs all video compression in hardware; on a 195 MHz R10000 system with an IMPACT Compression board installed, it is possible to record analog video input to disk in real time with only three percent processor utilization.
  • The IMPACT Video board: digital video I/O and links to IMPACT graphics and IMPACT compression. A system with an IMPACT graphics board, both IMPACT Video and IMPACT Compression connected properly can input analog or digital video, and compress it in real time or, (with the real time color space converter) pipe it directly to the graphics board, where it can be used as an OpenGL texture map. It can also pipe screen output to analog or digital video output, or through the JPEG compressors to disk.
  • The Real-Time Color Space Converter daughtercard for the IMPACT Video. Allows video from IMPACT Video to be used as a texture. This may be even rarer than IMPACT Compression.
  • The IMPACT Channel Option adds an additional channel of video output to any IMPACT graphics board. This allows a single IMPACT board to drive two displays, but does not increase the processing power of the IMPACT board, so doing 3D graphics on both displays simultaneously has a performance penalty. It is also possible to install two IMPACT graphics boards in one system. Theoretically, one could install two Solid IMPACT boards, each with the IMPACT Channel Option in four physical slots, driving four displays from one Indigo2 system.

External links

• Ian Mapleson's Indigo2 webpage (http://futuretech.mirror.vuurwerk.net/indigo2/)