28 Oct
2014
28 Oct
'14
2:03 p.m.
I've forgotten the details nows, but they also had some issues when running UNIX.
Steve Glaser and I chased those for a long time. The 60 had the HCM instruction sequences
(halt a confuse microcode) which were some what random although UNIX seemed to hit them.
DEC envisioned it as a commercial machine and added decimal arithmetic to it for RSTS
Cobol. I'm not sure RSX was even supported on it.
Ah, RSTS...the Really Sh-ty Timesharing System. An amusing UNIX story on that one.
Hopkins EE department was a RSTS shop running primarily the Basic Plus interpreter which
was the core of some classroom courses (especially the Freshman course: Modeling and
Simulation). When the the guys found out about UNIX they lobbied the department faculty
to switch to UNIX and they were told they could provided that Basic Plus continued to
run.
Amusingly, if you read the DEC processor handbook, it says the TRAP instruction is
designed to invoke system calls. UNIX did this of course. Amuslingly, the DEC
operating systems, including RSTS, used EMT to invoke system calls. The book says this
was put there to allow emulating other OSs. Well this made it relatively easy.
Basic Plus was calling EMT so they just had to catch the EMT traps and emulate the few
RSTS calls that Basic Plus needed to make. JHU/UNIX was born. It was a Version 6 UNIX
(which original system administrator John Day decided that 6.06 was a great version number
and he kept it through many software updates). Mike took over and stared advancing the
numbers again.
We also had an 11/40 (lacking memory management) running miniUnix. They also ran
miniUNIX in the Biomedical engineering lab on an LSI-11/03. I upgraded that lab to
11/23 running full up UNIX later on.
You may recall that the UID was stored in a (unsigned) char in those days. This was
problematic when you had a student body of a couple of thousand. The solution was a
kludge: "JHU Ownership." If your GID was over 200, both your UID and GID
were considered when computing identity. Obviously, newgrp was disabled for those
accounts and I spent many an hour trying various combinations of setuid/gid bits and
setuid/gid calls to see if there were any way to abuse that.