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[ih] BBN C-series computers

The C/30, indeed, started life by faithfully emulating the Honeywell
316/516 instruction set and hardware model so that we were able to run the
existing IMP code with minimal changes. However, once we got that working,
we then started taking advantage of the microprgramability of the hardware
to move significant portions of the code into microcode. We had a great set
of tools for profiling the code execution to see where we could get the
greatest bang for the buck by moving heavily executed code into microcode
(especially in the packet forwarding code path), and we also microcoded
some atomic operations like queue and stack management. I wrote some amount
of microcode myself, including the driver for the tape drive to be able to
remotely download new versions of the code onto tape, and reload the C/30s
from the tape drive.

One of the major differences between the C/30 and C/60 and C/70 was that
the C/30 didn?t have any disk drives, just a tape drive.

The C/70 was a general purpose UNIX machine. The C/60 was a cost-optimzed
version of the C/70 used to operate a C/30-based network, and it came with
the necessary network management software.


On Sat, Oct 21, 2017 at 1:28 PM, John Levine <johnl at iecc.com> wrote:

> In article <CA5F73E9-DD4E-4A68-8477-8296669EA955 at gmail.com> you write:
> >> 2. BBN started the BBN Computer Corporation to be a computer company
> >> with the MBB as the base of its systems.  One market was as a
> >> replacement computer to run the 316 IMP code in BBN's (separate) network
> >> business.
> It is my recollection that the C30 was a microcoded reimplementation of
> the 516.  The IMP code was so dense that it was easier to reimplement
> the hardware than the software.
> >The C/70 was, as Bernie Cosell noted in his email, a big improvement over
> running Unix on the DEC PDP 11/70.  Unfortunately, DEC came out with the
> VAX shortly
> >after the C/70 was completed which reduced the market opportunity for the
> C/70 significantly.
> I ran into someone I think at a Usenix meeting who groused that
> porting existing Unix code to the C70 was difficult because everyone
> unreasonably assumed that bytes were 8 bits.
> While it was certainly nice that the C70 let you run bigger individual
> programs than the -11, it was about a decade too late for a computer
> that didn't have eight bit bytes.
> R's,
> John
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