I was curious if anyone knew why?
I'm a far, far cry from being an expert—perhaps A/UX-curious would be a better label—but it is a very restrictive OS. In my initial curiosity, I was led to this very useful page:
https://www.aux-penelope.com/hardware.htm
It outlines the compatible hardware architectures and the minimum version of A/UX they run. The 610 (WLCD) series appear to be the 'lowest form' of Quadra/Centris supported. A full 040
is a requirement, as outlined on that page, as certain models/configs of qualified motherboards shipped with LC040s, swapping to full-040 silicon is essential. So based on that list,
Does it run on a Q605 upgraded to a full 040?
no, sadly. I'd be interested to know if anyone has done it... though I doubt it.
Also, pay attention to the other non-logic-board requirements: storage, optical, etc.
Again, it cannot be stressed enough that this was an
incredibly hardware-specific OS, not intended for the everyday Mac user. The late-model Quadras (63x/64x and their AIO counterparts) were a budget logic board design, and Apple
never intended for anything other than plain-Jane Mac OS to run on them. The development qualification and upkeep was, from all I've read up on its history, fraught. There was little sense, even in the 'go wild' days of Apple R&D, to justify the development cycles for expanding qualification to other models.
I sort of want to start again...