[pups] Unix and PDP11/20 (was PDP9?)

Carl Lowenstein cdl at mpl.ucsd.edu
Thu Sep 5 08:44:18 AEST 2002

> From: Dennis Ritchie <dmr at plan9.bell-labs.com>
> Subject: [pups] Unix and PDP11/20 (was PDP9?)
> Date: Wed, 4 Sep 2002 00:21:40 -0400
> I'm not positive about the logo on our first PDP-11.

The text accompanying the picture "Ken and Den" somewhere on your web site
says that the logo on your first PDP-11 was just "PDP-11" without the /20.

> On the earliest handbook I have, the front panel photo
> just shows "PDP11", though inside the handbook
> it does talk about the two models (11/10 and 11/20).
> Both had the same KA11 processor, but the basic
> 11/10 sported 1024Kw ROM memory plus a generous
> 128 words of RAM, while the 11-20 had
> 4096Kw core RAM, and the ASR33 Teletype was included.
> You could add more RAM to the 11/20.

I fear that you have suffered a "units slip" saying 1024Kw
and 4096Kw when you meant 1Kw and 4Kw respectively.

> Incidentally, the machine's handbook was a wonder.
> In 104 pages (each 5.25x8 inches), it described the whole
> system: not only the instruction set but the theory
> of the Unibus (including some logic diagrams) together with
> programming specifications for the TTY, the clock,
> and the paper tape reader.
> 	Dennis

Agreed, "PDP11 Handbook Second Edition" was a really good book
Occasionally I wonder if I ever had my hands on a "First Edition"
and threw it away when the second edition came out.  Not knowing
that both the computer and the handbook would become classics.

    carl lowenstein         marine physical lab     u.c. san diego
                                                 clowenst at ucsd.edu

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