Indigo R3000 was VME-based, a derivative of the 4D/35 and firends

Indigo R4xxx was a completely different architecture shared with the later SGI Indy

Both had GIO32 slots

Same case, same slots, totally different architectures inside

...and Turbochannel was originally the bus for the MIPS R3000-based Ultrix workstations; the Alpha firmware needed to be able to interpret MIPS machine code to speak to TC expansion cards.

Somewhere, I have a Turbochannel FDDI card taken from an AlphaStation 3000-an obsolete I/O adapter for a forgotten network protocol, running on a defunct CPU, with firmware written in the native language of an even more defunct CPU.