Ø When I was at Locus, where we did the AIX/370 and AIX/386 stuff Ron mentions we started over.  Charlie can correct me, but IIRC the compiler was IBM's and as Ron said, AIX/370 too lived as a VM 'service.'  I think I have mention on this list previously, it was targeted for the IBM University customers and was not marketed widely; which was a darned shame because it was a excellent product (and TCF was ahead of its time).    Some one on this lost mentioned needing tons of floppies to install AIX/386 which is was so wrong.   You needed only one, if you had another system (386 or 370 on the network), you just booted the new 'node' and let TCF take over.  You 'joined' the cluster, disk replication would start to fill your disk in. It was extremely fast and easy.  Oh yes - AIX/TCF supported mixed instruction sets between the 370 and x86! (TCF looked for the proper node that had the correct HW provisioning to execute any specific process).  We used to show it off at trade shows, including migrating people's vi sessions 'around' the world when we had a cluster that spanned different physical sites [great fun].    Interesting security flaw -- root on any node in the cluster (like a local 386 node) was the same as root on the 370 nodes.

It’s been decades (but I still have my IBM contractor’s badge my desk).    We  added the i860 modes to the cluster.   We actually used more of the 370 code on our nodes than we did the x86 code.   Gosh, somewhere I have the how to boot up a new node on the cluster instructions.    “SERVICE” isn’t the proper term (services were more along the lines of the print spoolers, and some of the MVS stuff).   AIX  ran as the guest operating system much as the other IBM OS’s (CMS, MVS, ….).     Yes as time went by I head they had managed to get AIX up on the bare metal.   I never used it that way.   The mainframes I was running AIX had other guest operating systems.    I’m trying to put out of my  mind the fast that I used to be responsible for an MVS system.

And yes, VM made things easier.    It got you slightly removed from the hardware.     The disk wasn’t that big of a thing.    AIX punted by not actually doing the tricky channel stuff like talking directly to the IBM terminals (3270’s) or 3705.   3705 programming was a black art even on the IBM native OS’s and then we had some funky third party (COMTEN) hardware to deal with.    AIX deflected all this by actually making the user facing stuff hang off the i860/i386 nodes.   

Conversely getting the IBM mainframe operating systems (notably VM/CMS, but to some extent MVS) to talk to the non-IBM world was equally interesting.   I remember talking extensively to Barry Appleman (VM’s TCP IP guY) about writing an X3270 xterm variant.    I remember him launching into the Monty Python pet store skit at the suggestion.