But in its way OS X was much more of a clean break: a whole new OS, ported to the old hardware, tweaked to understand filesystems and file formats and given a shallow cosmetic resemblance.
A/UX was a much tighter integrated system. Some of the OS functionality was provided by actual classic MacOS.
What was left, if that was removed, was a fairly unremarkable Unix for its time. You could even boot it in a sort of vanilla-Unix form.
E.g. for v3, top 2 rows (pics 1-6) are in Mac mode, bottom row (7-9) are in Unix mode. A bit like the ANS with AIX, there's little to appeal to Apple users here:
http://toastytech.com/guis/rhap.html
And there's some description of the emulation nanokernel:
https://en.wikipedia.org/wiki/Mac_OS_nanokernel
But in its way OS X was much more of a clean break: a whole new OS, ported to the old hardware, tweaked to understand filesystems and file formats and given a shallow cosmetic resemblance.
A/UX was a much tighter integrated system. Some of the OS functionality was provided by actual classic MacOS.
What was left, if that was removed, was a fairly unremarkable Unix for its time. You could even boot it in a sort of vanilla-Unix form.
You can compare and contrast here:
https://www.aux-penelope.com/screenshots.htm
E.g. for v3, top 2 rows (pics 1-6) are in Mac mode, bottom row (7-9) are in Unix mode. A bit like the ANS with AIX, there's little to appeal to Apple users here:
https://www.floodgap.com/retrobits/ans/aix.html