DEC MKA11 and/or M8261/M8163

Paul Birkel pbirkel at
Sat Feb 14 12:59:25 CST 2015

PS: Just noticed the Memory options in Table 1-3.

MKA11-AA is Single Port Memory and uses the Single Port Jumper Card.

MKA11-BA is Dual Port Memory and uses the Multiport Multiplexer.

MKA11-UA is Single port upgrade kit and includes a pair of port-buffers and
one multiport multiplexer :->.

MKA11-UB is Multiport upgrade kit adds another pair of port buffers; you
can apparently do this twice.  So I guess one Multiport Multiplexer handles
up to four ports.  Now ... how does two sets of six-bits fit into that

M8164 isn't mentioned anywhere, so I guess that's simply a general-upgrade
replacing M8159 that applies to either MK11 or MKA11.

On Sat, Feb 14, 2015 at 1:50 PM, Paul Birkel <pbirkel at> wrote:

> So ... I should have stretched my mind a bit more in the space of "stuff
> like an 11/70 but which is not an 11/70 ...".  Encountering even a bit of
> an 11/74 was simply not something that I ever considered.  Thanks for the
> pointer Johnny!
> Looking at the preliminary Docs, Figure 1-1, where a two-processor
> configuration is laid out, with two MKA11, it appears that they have their
> ports cross-wired and then driven from a panel-control of some sort.  So
> there's 6-bits for MK0A/MK1A, and then a separate 6-bits for MK0B/MK1B (see
> earlier response to Eric about the connector arrangements).  Not at all
> clear to me how that wiring relates to the description in 1.4.2.  Need to
> think about this some more ...
> It seems then that the Field Guide has both of these modules mis-assigned,
> and the second misnamed.
> I wonder if the relationship between the M8163 and M8164 is an either/or
> and they go into the same slot given that Table 1-1 mentions only a single
> Multiport Multiplexor (M8162) and the naming in Table 1-3 for the M8163 is
> "Single Port Jumper Card"?  I guess that's what you're thinking as well.
> What is the purpose of the "panel" Port Controllers, given that they seem
> to be not connected to any control signals from the CPU? (Figure 1-1)
> Does the "T" in the symbology in the Figure perhaps indicate
> "Terminator"?  If so, that seems to suggest that the signaling is out one
> control, into the second and then off "through" a terminator to the panel
> Port Control?
> Honestly, Figure 1-1 doesn't look to me like a shared-memory arrangement
> ... so I'm probably misinterpreting some of those lines at the moment.
> Thanks for all of the additional clues and pointers guys!
> On Thu, Feb 12, 2015 at 5:24 AM, Johnny Billquist <bqt at>
> wrote:
>> On 2015-02-11 20:55, Eric Smith wrote:
>>> On Sat, Feb 7, 2015 at 7:25 AM, Paul Birkel <pbirkel at> wrote:
>>>> I don't understand the role of the M8162 "Port MUX A module" and M8163
>>>> "Port MUX B module" that the field-guide claims to be part of the MK11.
>>>> They aren't part of the MK11 as far as any documentation that I've read
>>>> regarding it. [...]
>>>> Do these modules really belong to the MKA11, rather than the MK11?
>>> The MKA11 was the multiported version of the MK11, intended for
>>> multiprocessor (11/72 and 11/74) systems. it makes sense that it would
>>> have some "port mux" modules, though I've never seen any documentation
>>> on it.
>> I don't think that 11/72 is a valid designation. All documentation I've
>> read only calls it an 11/74, no matter how many CPUs you have.
>> You can find documentation on the MKA11 in the 11/74 documentation.
>> (See
>> EK-70MP-TM_PRE_1170mp_Prelim_Technical_Manual_1977.pdf)
>> And in there, you can find that:
>> M8162 is a "Multiport Multiplexor Module"
>> and
>> M8163 is a "Single Port Jumper Card".
>> So yes, both of these cards are for the MKA11.
>> I would guess that you use the M8163 if you have an MKA11 but just a
>> single CPU.
>>  Reportedly some 11/70 systems were sold to AT&T with the KB11-CM CPU
>>> and MKA11, apparently just as a way to use up the hardware that was
>>> built for the cancelled 11/74.
>> I've heard similar. And also that CPU cards for the 11/74 were installed
>> in 11/70 systems. The differences don't matter for normal operation, and it
>> will work like a normal 11/70. You can detect if differences if you try,
>> but the system will work like any other 11/70.
>> Only a few CPU modules differ between an 11/70 and 11/74 anyway.
>>         Johnny

More information about the cctech mailing list