> From: Jerry Weiss
> So it would appear the upgrade board makes provisions for both
> situations.
I'm not sure that the two situations that the upgrade board supports are in
fact different, from its point of view. (Assuming that the two situations you
refer to are the two different consoles.) Yes, the _system_ supports two
situations: i) the KY11-LA connecting directly to the backplane, and ii) the
KY11-LB going via the M7859; but the DEC CPUs don't seem to draw any
distinction between the two.
Looking at the KY11-LA prints, the connector to the backplane cable (the one
which is unused with the KY11-LB) carries signals like "Halt Request" and
"Halt Grant", which are generated in the M7859 (which has its own direct
backplane connection) when using the KY11-LB.
So as far as the consoles are concerned, those signals come to the backplane
via different paths, but as far as the CPU is concerned, it sees the same
things through its backplane connection, no matter which is in use - so how
would the upgrade board be any different?
The _only_ cable(s) that ever connect(s) to the CPU board (in the KD11-D or
KD11-E) are from the KY11-LB: those cables are the ones that carry the signals
to support the microcode single-stepping. How would the upgrade board use
these?
One thing that might help untangle the function of those two headers on the
upgrade board is to look and see what chip(s) they connect to. If they aren't
EIA transmitters/receivers, yes, they aren't serial lines. (I only suggesgted
that because I couldn't figure out what _else_ they could be.) Can that be
done?
Noel
