PDP-6s at MIT

Noel Chiappa jnc at mercury.lcs.mit.edu
Sat Dec 17 07:14:22 CST 2016

    > I suppose it's likely they both used the same master/slave
    > configuration.  However, there's one thing I found that may indicate
    > that the DM machine went in an other direction.

I think the latter may be true, I have this vague sense that the two DM
machines were never interonnected the way the AI pair were.

For one, the DM people didn't have a bunch of oddball hardware connected to
their main machine, the way the AI people did. (There was a special Evans+
Sutherland display processor, but that's about it. The ITS sources will
probably have a complete list, until the DM configuration section.) They also
didn't have as deep a bench of hardware people.

Also, I remember reading somewhere (it was decades ago, sorry, don't remember
the source) that AI's paging box was subtly different from the one on DM; the
AI one could IIRC, address 4 'moby's (a full PDP-10 address spare), and two (I
think? I'm pretty sure all the KA's had two moby's of main memory) were used
for the Fabritek 2-moby memory, one was for the PDP-6 (so the KA could see
into it) and one was for the PDP-11's. (AI had a number of PDP-11's attached
to it - one to drive the Xerox Graphic Printer, one to drive the Knight TV
system, and I think maybe one more, the so-called I/O -11 - or was that on MC,
which had two -11's - the standard KL front console -11, and I think one more?
I'm can't quite remember, although I'm pretty sure neither DM or ML had any
-11's. Anyway, on AI, the KA could see into the memory of its PDP-11's. If you
look at the ITS sources this probably is all laid out there.)

So probably the DM -6 and -10 were two separate machines.

    > MX kl10 (expand ML group to high performance)

Actually, this machine was named MC when it first arrived, and kept that name
until its 'replacement', a KS, arrived, _many_ years later. (They didn't want
to give the new machine a new name, since there were a ton of mailing lists on
'MC', and it was easier to swap the machine names.) It was renamed 'MX' at
that point. It was called 'MC' since it was bought for the Macsyma Consortium
(part of LCS, not sure if it was part of the ML group, it might have been).


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