HP2100A luser questions

Jay West jwest at classiccmp.org
Fri Nov 21 08:27:05 CST 2014

Tony wrote...
Anyway, I came across my HP2100A minicomputer, so I took a long look at it
(seriously, I must have spent a couple of hours pulling boards, etc). Some
day I would like to get it running again.

Congrats, the 2100 is a wonderful machine. IMHO, the
easiest/quickest/MostFunctional front panel ever on any computer. The "light
being the pushbutton" allows for really quick entry/changes and strong
visual cues. I find I can enter front panel code quicker on that panel than
any other.

I assume there's  no chance of me finding a top connector for the memory
system. Am I right that the only difference between the 2 flavours is the
spacing of the edge connectors on the PCB? Due to the fact that the
connector plugs into the core plane daughterboard, which is fitted on the
component side of the sense/inhibit board, so the spacing between the edge
plugs changes depending on whether the core is to the left or to the right
of the address driver. Both top connectors seem to be just pin-pin wired on
the PCB, but the manuals don't really mention them.

You may well be able to procure one. I have a source that may have one
available for sale, email me off-list for particulars. If that fails, there
is somewhat of a chance I may have a spare.

There is a tab on my A2 board telling me I have the floating point microcode
and indeed the
6 ROMs are fitted (in sockets) near the standard microcode ROMs. Was there
ever a published source listing of this? It would be interesting...

I believe the microcode listings are around. Can't put my fingers on it at
the moment.

One major problem concerns the power switch. I don't have the key, and it's
currently in the 'panel lock' position. Now, I can trivially jumper the
switch to enable the panel but I would rather not. 

I probably have a spare key... but at the least, I'm sure I could loan you a
key so you can have a copy made.

Were all 2100A's keyed alike (like all DEC machines were)? If so, does
anyone have the key cutting data?

I am not positive, but I believe they were all keyed alike.

With the configuration I have (assume I can get 32K words of core, and have
the I/O cards I listed) what can I run on it?

The standard diagnostics library (the one that uses the diagnostic
configurator, not the standalone diags) is kinda sorta an operating system
in and of itself. Fun to play with. I can strongly recommend HP-IPL/OS. It
will run on even less hardware than what you have, yet fully supports
maximum hardware configurations. It is pretty much "Forth", and very very
well designed. You can pretty much do anything with that.


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