[TUHS] AOS and IBM/RT [Re: Amdahl UTS, AIX/370, AIX/ESA

[Dan Cross]

On Thu, Nov 21, 2019 at 8:07 AM Brad Spencer <brad at anduin.eldar.org> wrote:

> For a brief time a long time ago, I used a 4.3BSD based Mt. Xinu, MACH
> microkernel, OS on the IBM-RT as an alternative to AOS.  Ran well
> enough, but was disk and memory constrained.  We had source to much of
> the system (or perhaps all of it, don't remember), but I seem to recall
> that compiling it was a big pain.  Something like you had to use a
> specific compiler (perhaps referred to as High C??  hc command perhaps)
> to compile some of the source.  gcc had a backend for the ROMP
> processor, but it had a hard time making usable binaries.  I think that
> some variation of pcc was the usual compiler.  I remember it being
> pretty stock 4.3BSD with NFS and minus YP/NIS.  We used them mostly as X
> terminal workstations.
>

"High C" (or perhaps "Hi C"? It's been a while...) was the name of the
system compiler on AOS; I thought it was installed as `cc`. I don't recall
a pcc-derived compiler, but apparently such a thing did exist and some
documentation says that High C was installed as `hc`, so my memory may be
off. This old post describes RT compilers:
https://groups.google.com/d/msg/comp.sys.ibm.pc.rt/u7DUwY5U9kQ/uVqLP9FhqMEJ

Hi-C was sort of an odd compiler. I gather IBM outsourced the development
of it to some third party (MetaWare) which was founded by very religious
people, and I have a vague memory of some of the documentation or perhaps
even error messages making biblical references.

The kernel had to be built with High C, if I recall correctly, though GCC
worked OK for producing userspace binaries. I don't recall what the bug
was, but it was eventually found and fixed. Perhaps it had to do with
incomplete register saves on function entry interacting poorly with
interrupts or something.

Some RT enthusiasts kept those machines running well beyond their prime.
Why? I'm not entirely sure; as you say, they were memory and disk
constrained. They were also very slow. Anyway, I have some vague
recollection that at some point the bug in the compiler was fixed so that
GCC could produce a working kernel; nascent NetBSD and OpenBSD ports were
planned, but I don't think they ever went anywhere.
https://www.openbsd.org/romp.html exists, though I don't know that the
NetBSD people ever got beyond the talking stage. The OpenBSD-romp mailing
list had some interesting information, but I can't find archives anymore.

Oh well. The RT was an interesting footnote in the history of computing,
but it seems that, as a workstation, it was too little too late by the time
it actually hit the market. Had they released it a few years earlier?
Perhaps they could have cornered the market.

        - Dan C.
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