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2/ The first entries in the Indigo 2 line came in teal cases. They used some variant of the MIPS R4x00 architecture, and supported largely the same graphics boards as the Indy line: (2D-accelerated) 24-bit XL, (3D-accelerated) XZ, and (even faster-accelerated) Elan.

3/ This was no coincidence, as the initial line of Indigo 2 machines were, broadly, the same underlying architecture as the lower-profile and lower-cost Indy machines: The fundamental differences involved an internal optical drive bay, a second SCSI controller, and an EISA bus.

4/ As an aside, the EISA bus occupied the same segment of the machine's memory map as the Video-In No-Out ("VINO") chip on the Indy, which is fundamentally why the Indigo 2 line lacked such capabilities without a dedicated capture card.

5/ SGI started experimenting with the next generation of MIPS chips beyond the R5000, and they hit upon the R8000: A multi-chip solution with phenomenal floating-point performance. They released this as the "POWER Indigo 2" line. Same teal case, but a different CPU.

6/ This line did not last long, however. Educational institutions, in particular, quickly found that the POWER series of MIPS processors had some really gnarly floating-point bugs despite the performance. This can be confirmed by looking up contemporary posts on Usenet.

7/ Lastly, once SGI finally found a workable 64-bit architecture in the MIPS R10000 series, they released the "Indigo 2 IMPACT" line, in its notably different purple/mauve-themed case. It supported a much different line of graphics cards, to boot.

8/ The Indigo 2 IMPACT line supported, broadly, three graphics options: Solid IMPACT (SI), High IMPACT (SI), and Maximum IMPACT (MXI). High IMPACT AA is omitted for brevity. SI lacked texture acceleration, HI had it as an option, and MXI had texture acceleration standard.

9/ For all intents and purposes, the Indigo 2 IMPACT was broadly similar in CPU and GPU power to the initial run of Octane machines. It used the same MGRAS ("Mardigras") graphics subsystem, the same 64-bit R10k CPU. The differences were in bus architecture and memory bandwidth.