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
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.