Back around 1989 our company was provided the AIX 370 and PS/2 source code.    This was a distinct code base from either of the RT UNIXes.    It was a pretty straight-forward UNIX kernel with what IBM termed the Transparent Computing Facility (derived from the UCLA locus stuff).    We were porting it to an IBM-produced four-processor i860 board called the W4.    It was fairly neat in that the file system could support hidden versions of the executables for each of the different platforms, and if you invoked one that didn't exist on your local hardware, it automatically ran it on one where it existed.

The W4 was a microchannel card that had its own frame buffer (I wrote an X Server for it) but lived inside a PS2, so during the port, it was easy just to use the 386 versions of the bulk of the executables.    When working at IBM's Palo Alto facility I could even execute on the 370-variant there as well.   The W4 kernel looked more like the 370 than the 386 interestingly.

I hacked on the -mm macro package to make it stylistically look like IBM's manuals so we could produce our documentation to look like there's.   We had to have our facility inspected to hold IBM's source code (I referred to the room as the toxic waste dump).    Our other joke is that IBM had a multiplexed console that they called the HFT (High Function Terminal).   When I wrote the simple console for the W4 kernel, I called it the LFT.