DEC MKA11 and/or M8261/M8163

[Eric Smith]

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.