IP22 is Silicon Graphic's software archicture name for the hardware sold as Indy, Indigo 2 and Challenge S. Modulo peripherals these systems are all very similar. Various Linux distributions will easily install on IP22, among them the Debian MIPS port.
Over the years Indy systems have been equipped with a variety of MIPS processor starting with the 100MHz R4000PC over R4000SC, R4400PC, R4400SC, R4600PC, R4600SC, R5000PC and R5000SC. Indigo 2 systems use the same system board as Indys but have only been been made with R4000SC and R4400SC processor modules.
The POWER Indigo 2 is based on the IP26 system board and comes with the R8000 processor. The R8000 is in many ways a unique MIPS processor and currently only partially supported by Linux.
The architecturally very similar Indigo 2 R10000 is based on the IP28 system board and has a MIPS R10000 processor. This system represent a very special case and therefore isn't supported yet by Linux.
IP22 boards have two memory banks; each bank consists of 4 memory modules and if populated must be fully populated with fast page mode 36-bit wide PS/2 style memory modules from 4MB to 32MB size. Memory configurations between 16MB and 256MB are support.
The board in the Indigo 2 is similar but has third memory bank, therefore it's maximum memory configuration is 384MB.
IP26 and IP28 boards also have 3 memory banks each 4 modules but support 64MB memory modules also increasing the maximum memory capacity to 768MB.
Support of more than 384MB memory requieres a 64-bit Linux kernel.
The Indy comes with the entry level XL (Newport) graphics which exists in 8-bit and 24-bit variants, and is basically a 2D card. There is also the XZ (Express) which is a 3D card with geometry processing and Z-buffering, and 24-bit color depth (and is unsupported under Linux). The Indigo 2 systems can use both of these options as well, however there is another one. The IMPACT is the best 3D graphics board available for these machines (and is also unsupported under Linux, although large parts of code might be shared with the Octane driver). Finally the Challenge S which is a headless compact server system (based on the Indy motherboard).
Challenge S, Indy, Indigo 2 and Indigo 2 R10000 are all equipped with an on-board WD33C93 SCSI controller. In addition to that the Challenge S has a second SCSI hostadapter supporting fast and wide SCSI, the WD33C95. Linux supports the WD33C93 but not he WD33C95.
All IP22 systems come with an onboard Seeq 8003 network controller. The Challenge S being a server system comes with a second 8003.
All IP22, IP26 and IP28 systems use ARC firmware.
Silicon Graphics, Inc. generously granted permission to distribute hardware documentation for the Indy. All files are as provided by Silicon Graphics except the virtual dma specification of which no electronic copy could be found, so it has been re-created.
The documentation for Vino is available in form of several postscript files, one per page:
IP22 has forgotten it's ethernet address
IP22 uses the Dallas DS1286 RTC chip to store time and firmware variables. This chip contains a builtin battery for ten years but by now this decade is almost over and experience has shown that some of these RTC batteries have a much shorter battery life, so the RTCs start becoming forgetful. Software may also accidentally have overwritten the RTC's content.
If you have determined that a defective RTC chip is the cause of the problem you can get a new RTC from http://www.maxim-ic.com/ or other sources. Be paranoid, make sure you don't get a part that has been sitting on a shelf for long years.
This is how to reprogram the RTC chip. Assuming your ethernet address is aa:bb:cc:dd:ee:ff
fill -w -v 0xaa 0xbfbe04e8 fill -w -v 0xbb 0xbfbe04ec fill -w -v 0xcc 0xbfbe04f0 fill -w -v 0xdd 0xbfbe04f4 fill -w -v 0xee 0xbfbe04f8 fill -w -v 0xff 0xbfbe04fc
With this command you can verify the content of the chip's NVRAM:
dump -w -x 0xbfbe04e8