30 Dec
2016
30 Dec
'16
12:20 a.m.
Yes. Before the networking code in, the kernels on the non-split I/D machines got by
with using a couple of the segments to make code overlays. The mbufs required a overlay
register of their own and once you got the minimal data segment as well as the top one for
the stack, you just couldn't do it with 8 total. With Split I/D you had 8 code and
8 data segments and that you could make work.
It was a boon for me. I had started with Noel's MIT C Gateway but abandoned it for
my own "Little OS" based version (Noel had been exiled to the Bahamas or some
warm place and the MIT code was lacking in some necessary featuers for us). I took all
the non-split I/D machines around the lbs... everything from PDP-11/23's and
11/24's up to some 11/34's we had. Eventually, UNIX got too big for even the
11/70's that were left, and those were turned into ( rather compute heavy) routers as
well.
The 11/34's were an another amusing piece of recycling. A contractor sold those to
the government to be graphics remotes for our CDC 7600 mainframe. Each one had a Vector
General graphics station, an 11/34 with a couple of RK05's, a punched card reader,
and a DQ11 and 56KB modem. The contractor couldn't get the things to work with the
mainframes, and Mike Muuss's standard answer to extra compute hardware was to put
UNIX on it. We did, and Mike wrote the early version of the BRL CAD for the Vector
General (this was 1980, I remember him giving a talk on this at the Univ. of Delaware
UUG). We took the DQ/modems to make an early BRLNET (pre-IP) link. Late one summer
evening Mike and I wrote a version of ASTEROIDS for the system. We finished about dawn,
and when the real ballistic researchers came in that morning to play it they decided our
physics was all wrong so by the time we returned later, it had been recoded. Such was
the lab in those days.