The predecessor of the AS/400, the IBM System/38, was a really very radical architecture for 1978/1979 it had capability based addressing and a file system based on Relational Database concepts.
Some of the same leadership that ran that project (Glen Henry) was also respononible for IBM's adoption of Unix.
This IBM Unix system, AIX (1986), was designed to run on another interesting hardware platform, the earliest generation of IBM's RISC hardware PowerPC. Which in turn evolved from IBM's (1975) 801 system (John Cocke--who won the Turing Award in 1987 for invention of RISC) was responsible for the 801. I remember him coming into my office to talk to me about some ideas he had for a high capacity disk drive around 1987 when I was working on AIX.
