PDP-6s at MIT

[Noel Chiappa]

    > 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.

I wasn't able to track down the source of that, but reading ITS sources did
confirm (see SYSTEM;CONFIF >) that the AI paging box had one more bit of
output address than the ones on DM and ML. And the PDP-6 memory appeared at
03000000.

I now recall that later in the AI KA's life, the Fabritek ('Moby') memory got
flaky, and it was replaced with a kludge (done by HIC, according to the ITS
source) which used a number of LISPM memory cards.

    > (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?

So the I/O-11 code (see SYSTEM;IOELEV >) ran on 3 PDP-11's; two on MC (one
was the front console, interfaced through a DTE20, and one an I/O processor
interfaced through a DL10 - this latter one was used to hook up to the CHAOS
network).

The other machine running this code was the so-called "CHAOS-Ether-Gateway"
machine on AI (AI had two other -11's, as above). I had this vague memory that
that machine was there before it was hooked up to either the CHAOS net, or the
(3 Mbit) Ethernet, and it was doign something else, previously - but maybe not
- maybe it was added to give the AI KA access to the CHAOS network?


    > From: David Bridgham dab at froghouse.org 

    > I thought I'd heard that the 10s were connected to the Chaosnet through
    > 11s running MINITS.

That would have required building a 10-11 interface for them.. :-)

But if you look in SYSTEM;CONFIF > you can find this:

  IFE MCOND MLKA,[
  ..
  DEFOPT CH10P==1		;CHAOS NET VIA PDP-10 I/O BUS, NOT FRONT-END

and then in SYSTEM;CHAOS >

  SUBTTL CH-10 HARDWARE DEFINITIONS
  IFN CH10P,[
  CHX==470	;I/O DEVICE NUMBER
  ;CONI/CONO BITS

So there were PDP-10 I/O bus CHAOS network interfaces. (Although I have
absolutely no, zero, memory of them! :-)

	   Noel