The collected works of nyef - Page 2

My theory is that Apple assumes that everyone just uses recent Apple laptops. One of the reasons I'm running Linux on my Mini 2010 is that OSX post-10.6 or so has broken power management (no suspend-to-disk) on that hardware, which was a major part of my use-case when I bought it.
Okay, how about having another system (say an RPi or similar) monitor the UPS and when it has a power failure it can ssh over to the OSX box and issue a shutdown?
Honestly, if you're looking to run Linux on SGI hardware, particularly if you want graphics support, you can expect to be doing at least some hacking to get it to work. Possibly a lot of hacking. Admittedly, my experience thus far has been Octane and Origin hardware, not O2 or Indigo2, but there it is. And, IIRC, there's some issue with R10k Indigo2 and non-coherent DMA and speculative execution and cache pre-fetch, and I have no idea what the status on that is.
IIRC, the serial port initializes at 9600 baud, but I could be wrong. Definitely 8-N-1, though. It's been a little while since I last used a serial console for an Octane. You will probably need a "null modem adapter" or similar.

Note that the PROM will not initialize the video system unless a PS/2 keyboard is attached. Mouse optional.
Fuel? IIRC, the serial console is routed to one of the serial ports on the back panel, NOT to the L1. Somewhat of a nasty surprise, really, and I don't know how to change it, but there it is. Power up via the L1, then use a second serial connection or unplug/re-plug to the other port to get at the console.
25 years? I'd suggest that any electrolytic capacitors in the system are likely to be marginal at this point, and would be a good first thing to swap out to see if it helps.

The 3.6v battery being dead shouldn't prevent the system from starting up, it just keeps it from remembering things like which disk to boot by default, what time it is, and so on.

If I recall correctly, there may well be a second power button on the machine itself. Even with the power buttons on the keyboards, there was usually a second way to power the system up.
First thing that I might try is to pull the hard drives. If there's no drive to boot from, it has to stop to ask what to do. From there, you can get to the PROM console and disable auto-boot. Shut back down, put the drives back in, and go from there.