Sadly, they don't really HAVE much; Rackable shredded[1] all of their old SGI docs circa 2010. The only reason the Indy works in MAME is because SGI released docs for porting Linux to it.
At least one person is working on O2 support in MAME[2][3]. But it's a tooth-and-nail fight against lost knowledge.
[1]https://forums.irixnet.org/thread-3098-post-21822.html
[2]https://nitter.unixfox.eu/TheMogMiner/status/151532020941397...