Need DM11 documentation

Bob Smith bobsmithofd at
Wed Oct 2 10:23:20 CDT 2019

I believe that DM11 was designed by Vince Bastiani, (SP) after the
DM11 he designed the UART - that is another story - with one or more
The backplane - as I recall - was dedicated to the DM11 Comms interface.
here is the board list

M7240    DM11 U   DM11-A control

M7241    DM11 U   DM11-B control, quad

M7242    DM11 U   DM11-C control

M7243    DM11 U   DM11 transmitter D

M7244    DM11 U   DM11 transmitter E

M7245    DM11 U   DM11 receiver, quad

M7246    DM11-BB U   Modem control scan, 16 lines, DM11-BB

M7247    DM11-BB U   Modem control MUX, 8 lines

On Wed, Oct 2, 2019 at 10:33 AM Noel Chiappa via cctalk
<cctalk at> wrote:
> Hi, does anyone out there have any DM11 documentation? The only thing I could
> find online is the "DM11-BB model control option manual" (DEC-11-HDMBA-A-D) -
> and it's the impetus for this request, actually.
> One page 1-5, pg. 15 of the PDF, it has a diagram of which boards go into
> which slots on the DM11 backplane - and ir has _two_ boards marked M7245! So
> something's clearly wrong.
> The DM11 is a fascinating oddball of an interface, BTW. (It's in the 1972
> edition of the "peripherals and interfacing handbook".) A lot of its internal
> state is kept in main memory, and accessed via DMA! This includes the incoming
> data shift registers!!! So it can really chew up a bus - probably why it was
> dropped ASAP. I guess when it was done, memory in chips must have been expensive
> and/or not very dense; and it must have been before the first UART chips.
>        Noel

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