There absolutely was, and is, an AS/400 machine. Originally, it was a custom (and kinda weird) CISC processor and associated specialized I/O architecture. Now

There absolutely was, and is, an AS/400 machine. Originally, it was a custom (and kinda weird) CISC processor and associated specialized I/O architecture. Now it's a customized Power derived processor and a somewhat more standards oriented I/O architecture. There is an extremely well defined abstraction layer that the applications run on top of that allowed them to be migrated, but it's intimately tied to the physical implementation of the underlying AS/400 hardware. I'm not an AS/400 expert, but did work in one of the largest AS/400 shops in the world for quite a while. The AS/400 folks definitely didn't live migrate apps CISC->RISC when they upgraded. Sat is lots of change management meetings there. Could they have? Dunno. But they sure operated like that was SOP.