UK PDP11 wanted

Noel Chiappa jnc at
Sat Apr 11 09:26:45 CDT 2015

    > From: Pete Turnbull

    > Are you confusing it with a KDJ11-A ... But this is a KDJ11-B

Nope. Have several of both (IYWR, it was my looking at my various M8190's
that led me to the conclusion that all M8190's, no matter the version, can
do PMI).

    > Basically what makes the difference is whether it's using PMI memory or
    > QBus memory. ... If you change the config to not use PMI, an 11/83
    > becomes an 11/73.

After thinking about this for a while, the terminology does now make sense to
me, if it's applied to _systems_, not _boards_.

An 11/73 is a _system_ with no PMI memory usage (one can of course plug PMI
memory into a system with an M8192, but that won't make it use it, i.e.
become an 11/83). An 11/83 is a _system_ with PMI memory in use (an M8190,
plus PMI memory).

But I still think of the _cards_ as either an '11/73 CPU' (M8192) or
'11/83-84 CPU' (M8190).

The '11-83/84' part does lead to an interesting question: what do we call a
_system_ with an M8190, a KTJ11 (M8191), and no PMI memory, only regular QBUS
memory? (Not sure if this will work... but it should, I'll try it soon and
see. Also, this part is for fun, not serious!)

Analogizing to the 73/83 distinction, one might say that it's not an 84, but
a '74'... but that number is already taken! :-)


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