11 Nov
2017
11 Nov
'17
1:20 a.m.
I started in 1977 at UC Santa Barbara with Unix V6
that was running on a
PDP11/45 just during the night. The rest of the time it ran RSTS/E. In fact, there was a
sign that said "Oh say can you C by the dawn's early light" on the wall
because the time you were able to learn C was in the early
morning hours.
Amusingly, the way UNIX got installed at JHU was on the condition that Mike get Basic Plus
from RSTS/E to run on it. This turned out to only require two modifications. The
first was the addition of a system call to turn off the UNIX stack segment. The second
was to emulate enough of the RSTS system calls. This turned out to be fairly
straightforward because RSTS like most of the DEC operating systems used EMT to trap into
the kernel whereas UNIX used TRAP. I've never understood why DEC operating systems
used EMT, but it worked out for us.
Years later during the UNIX port to the HEP, we ran UNIX at night while the ersatz HEPOS
(fortunately abandoned) ran in the day time. The Denelcor guys would know we were still
up because when they hit ENTER on their terminals the OS would print: HEP, two, three,
four (hey, we were employees of the US Army, albeit civilians).