This is key. The AS/400 was never as documented as the IBM mainframe lines. I suspect the 360 open documentation was forced upon IBM by the many antitrust lawsuits. The AS/400 and its ancestors were never subject to these pressures.
There was more documentation available for System/38. Apparently, System/38 even had source code available on microfiche. (Unclear who if anyone still has it in their possession.)
By the time AS/400 came along, IBM had already become a lot more secretive. But CISC AS/400 was essentially System/38 Version 2.0, so a lot of the System/38 information still applied. It was more a matter of studying the system to work out where the changes/extensions were.
And RISC AS/400 was about as secretive, and less of the old System/38 documentation is applicable. On the other hand, it has a lot in common with AIX and Linux on POWER.
One of the more amusing oddities of AS/400, in my opinion, is some small part of it is descended from OS/2: if you look at the system header files, you will find very vestigial copies of a small number of OS/2 headers – bse.h, bsedos.h, bseerr.h. However, although this basic structure of header files is copied from OS/2, almost all the functions are missing–only two actual OS/2 API functions are present (DosSetRelMaxFH and DosSetFileLocks). My guess is at some point they planned to port more OS/2 APIs to AS/400, but hadn't got very far when they abandoned the whole idea.
Always look forward to your comments on IBM i, they've always got neat bits of trivia.
I wonder what they were going to do with the OS/2 bits? My two guesses:
I recall IBM had some crazy idea called Workplace OS to somehow unify all their OSs as personalities on top of a microkernel - I think the one from Taligent/Pink.
Or for OS/2 for the x86 servers on PCI cards for AS/400s.
> Always look forward to your comments on IBM i, they've always got neat bits of trivia.
Thanks, nice to know someone out there appreciates them :)
As to the headers, I really don’t know what they were planning.
However, one thing I do know - AS/400 and RS/6000 systems had service processors - a little x86 box which ran its own operating system and was in charge of tasks such as booting (IPL) and hardware diagnostics. Both CISC and RISC AS/400 systems had them. Mainframes had them too; for a long time the mainframe service processors ran OS/2, although more recently they migrated to Linux. I don’t know what AS/400 service processors ran, but maybe some of them did run OS/2.
The ILE layer (like a C runtime library but multilingual rather than C-centric) was (in part) shared between OS/2, OS/400, OS/390 and VM/CMS-although on OS/400 that term also got used to refer to the new version of the MI bytecode that shipped with RISC, which went far beyond the language runtime component shared with other platforms. It is also called CEE, and SAA Language Environment.
How much any of this explains the presence of those OS/2 headers, I don’t know.
> I recall IBM had some crazy idea called Workplace OS to somehow unify all their OSs as personalities on top of a microkernel - I think the one from Taligent/Pink.
It actually briefly shipped as OS/2 PPC Edition, although that was discontinued while still essentially in a beta state. It was a port of OS/2 2.x to run on top of Mach. It could also run DOS and Windows 3.x apps using CPU emulation (possibly it might have done so natively if they ever ported it to x86.) IIRC, some internal work was done on an AIX personality although it never shipped; Mach always had a POSIX personality, but based on BSD not SysV, so making it compatible with AIX for RS/6000 was in principle feasible even if they never finished it. IBM actually did briefly ship an AIX based on Mach, AIX/ESA, for IBM mainframes, which was based on OSF/1. (Albeit, historically AIX was just a brand, so not sure how compatible AIX/ESA was with the AIX we all know and love.)
From what I’ve heard, although the long-term plan was to port OS/400 to run on top of Workplace OS too, no actual work on it happened before the whole idea was cancelled. And I don’t know if there was any ever any plan to port OS/390 to run on top of Workplace OS, but I doubt that would have ever happened, even in an alternative timeline in which Workplace OS actually succeeded and ended up swallowing all three of OS/2, AIX and OS/400.
> Or for OS/2 for the x86 servers on PCI cards for AS/400s.
Yes, although I believe that while OS/2 was supported (at least at one point), NetWare and Windows NT were far more common.
This is key. The AS/400 was never as documented as the IBM mainframe lines. I suspect the 360 open documentation was forced upon IBM by the many antitrust lawsuits. The AS/400 and its ancestors were never subject to these pressures.