I also own and one of the Altos 486 from 1984. Its still running, but I am missing one fan. My room seems to be cold enough to run the computer for some time with XENIX. I am pretty sure Jeff Nisler has a lot more information about this "pretty one" but if you need some information or photos/video feel free to ask.

Altos 186 and 486 systems did indeed run the Intel 80186 processor, which were passed over by the PC world.

Typically there would be one to four terminals attached, one of which was the system console. The version of unix that it ran was a port of Xenix, which was Microsoft''s port of Unix. Yes it was "real" unix, albeit a somewhat limited one. However, most unix software could be made to run on it.

Altos computers of this era were Intel based but most of them were not "IBM compatible." Altos did not see any need to do that since their machines were never intended to run MS-DOS.

I worked at Altos when the 186 system came out. I porterd a version of the Pick OS to it in 1984 (a solo effort, which was never offered for sale). And I can tell you why it was a slow pig running zenix - the size was made small by removing hardware to a bare minimum, and in the balance the main cpu had to also be the CRT controller - the OS had to sit 2nd seat to the controller, or you wouldn''t see anything.
I have one of the prototypes, and it still works.