DEC MKA11 and/or M8261/M8163

Paul Birkel pbirkel at
Mon Feb 16 05:39:59 CST 2015

Regarding cable coloring, the fact remains that the M8159 Data Buffer has a
J5 Berg connector down over tabs E/F, whereas both the M8158 & M8159 have
their J1/2/3/4 data/address Berg connectors up over tabs A/B/C.  I'd say
that the color-differences happen to be significant in this case, but only
because they happen to align with the location of J5 :->.  Agree that
what's happening, color-wise, over the upper-tabs doesn't _seem_ to be

Since you've raised the topic of the Box Controllers, I see 16 (or 8
top-over-bottom pairs).  Isn't that enough for 4 MK11 (or MKA11)?

Note that 1170mP_Jul77_text.pdf also includes some additional MKA11
information, and improved diagrams.  Interesting comments regarding initial
consideration of developing a MP based on the 11/34.

On Mon, Feb 16, 2015 at 3:27 AM, Eric Smith <spacewar at> wrote:

> On Mon, Feb 16, 2015 at 1:05 AM, Paul Birkel <pbirkel at> wrote:
> > Notice the two unused connectors on the M8162 there in the middle slot
> > (#15).
> >
> > As this looks like an operational configuration, I infer that those two
> > connectors are used for ... nothing?  Test points (through series
> > resistors)?
> >
> > I see (how can one miss!) the address and data ribbon-cables.  The
> > remaining white ribbon-cables must be for the box controllers. So, that
> > looks like a 1Mw configuration.  Maybe 1.5Mw if, as you suggest, you're
> > careful?
> It appears to me that the off-white or light-grey cables are address
> and data cables, just as the grey ones, and the color was simply what
> was available at the time, or from a different cable vendor. The other
> boxes show different mixes of shades of gray for their cables.
> I believe that the molex connectors on the card in slot 15 are for the
> control box, and were either removed for the photograph, or were not
> necessary for the operation of the machine.  Note that CPU A and B do
> not have fully populated memory control panels, which suggests that
> the memory control panel wasn't strictly necessary for machine
> operation, though obviously very desirable for diagnostic purposes.  I
> don't really know, but if I'd designed the MKA11, I would have
> designed it so that without the controller connected, all ports are
> enabled.

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