What was a Terminal Concentration Device in DEC's products?

Paul Koning paulkoning at comcast.net
Mon Jan 31 08:23:25 CST 2022

> On Jan 30, 2022, at 2:43 PM, Chris Zach via cctalk <cctalk at classiccmp.org> wrote:
> ...
> From what I can see, the the kmc11 was an M8204 single board which is different from the 8200 used  in the dmc11. I had a DMC11 somewhere.
> From the books, the kmc11 had an "lsi11 on board", 1k of 16 bit ram, 1k of 8 bit data memory a 300ns cycle time, 16 bit microprossor with a 16 bit micro-instruction bus and 8 bit data path. This is according to the 1980 Terminal and Communications handbook, so it's a few years after the 1976 timeframe of Sha Tin.

A KMC-11 has no resemblance whatsoever to an LSI-11 or any other PDP-11 processor.  It's a custom microcontroller designed to be a coprocessor on the Unibus.

The DMC-11 processor card is not quite the same thing as a KMC-11; its firmware is in ROM rather than RAM, for one thing.  I don't know if there are any subtle instruction set differences.  Certainly the architecture is at least mostly the same; this can be seen from the fact that RSTS at startup probes various internal state of the DMC-11 by making it execute instructions, and those instructions can be readily understood by reading the KMC-11 manual.

It looks like the DMC-11 had a 1k program ROM, the KMC-11/B a 4k RAM, and the DMR/DMP microprocessor seems to be 6k ROM (the drawings are a bit confusing).  A consequence of the tiny program memory in the DMC was that the high speed version had a couple of limitations and bugs, described in the DMC-11 microprocessor manual.


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