DEC MKA11 and/or M8261/M8163

Paul Birkel pbirkel at
Mon Feb 16 02:05:14 CST 2015

Notice the two unused connectors on the M8162 there in the middle slot

As this looks like an operational configuration, I infer that those two
connectors are used for ... nothing?  Test points (through series

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

Agree about the missing documentation :-<.

Thanks for the better pic-pointer; knew that I can seen those in the past
but couldn't recall where (and Google didn't help).

On Sun, Feb 15, 2015 at 8:56 PM, Eric Smith <spacewar at> wrote:

> It appears that the module utilization of the MKA11 is significantly
> different than the MK11, so it must have a much different backplane.
> The photo of the MKA11 only shows eight storage array modules, in
> slots 9-12 and 18-21, though slots 5-8 and 22-25 might also be
> available for storage array modules. The memory bus cabling is
> obviously quite cumbersome, and adding storage modules in slots 22-25
> looks like it could exacerbate that problem.The MK11 supports 16
> storage array modules in slots 2-9 and 18-25. The module assignments
> for the non-storage modules also appear to be different.
> It's a shame that the KB11-Cm and MKA11 field maintenance print sets
> aren't anywhere to be found. While the available 11/74 documentation
> offers a description of how the KB11-Cm differs from the KB11-C
> (mostly interlocked ASRB and cache bypass), it's a shame that we can't
> study the actual details of how those changes were implemented.

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