> the clients inventory system ran on an AS/400 and I knew literally nothing about IBM mainframes
I'm going to be "that guy": The AS/400 (nowadays System i) is not a mainframe but the last standing member of the family of midrange (outside of IBM called minicomputer) systems. (NonStop and OpenVMS - and probably something else I don't know about - are still somewhat around, but nowadays they run on more or less microcomputer systems).
It's just IBM i now. I believe it was (not including System/38) AS/400-AS/400e->eServer iSeries->eServer i5->System i5->System i->i.
Nonstop has run on X86 systems for about 10 years now, but I don't think they were ever considered 'mid-range'. I think they usually were referred to as mainframes, although the hardware architecture was totally different.
I personally thought the AS/400 was midrange. That's how a co-worker characterized it when he left us to work on OS/400 development (way back in the 1980s).
IBM's own "History of AS/400" web page sort of implies it's midrange:
"For the first time, small businesses, city governments and other medium-size enterprises could set up their own computer networks and connect them to workstations, printers, file servers and even other networks — all running four times faster than what was previously possible."
Maybe System i is more mainframe-y than the original AS/400.
The question got me looking at old AS/400 manuals on bitsavers, and there is some interesting stuff. From the AS/400 handbook:
- Layered machine architecture. This insulates users from
hardware characteristics. It enables them to move to new
hardware technology at any time, without disrupting their
application programs.
- Single-level storage. Main storage and disk storage appear
contiguous. An object is saved or restored on the system via a
device-independent addressing mechanism
- Operating System, OS/400, is a single entity, fully integrating all
the software components (relational database, communications
and networking capabilities, etc.)
I agree with you that AS/400/i has always been called mid-range. I was actually referring to NonStop as usually being called "mainframe" not mid-range, or mini-computer, at least the early pre-RISC models. It's another interesting computer architecture.
For more on the AS/400, there's a book by the lead architect of it, Frank Soltis on archive.org that goes into a lot of detail. It is really quite different from anything else.
With 128 bit pointers encoding security and providence information. And a unified memory space, no files, just addresses with RAM as a cache for persistent disks. Might as well be from 2080.
I'm going to be "that guy": The AS/400 (nowadays System i) is not a mainframe but the last standing member of the family of midrange (outside of IBM called minicomputer) systems. (NonStop and OpenVMS - and probably something else I don't know about - are still somewhat around, but nowadays they run on more or less microcomputer systems).