HP2100A luser questions

tony duell ard at p850ug1.demon.co.uk
Wed Nov 19 15:43:10 CST 2014

I am still unpacking after the move....

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.

I have the standard 8 CPU boards, and the 12895 DMA board. I almost have 32K of core. What I 
mean by that is that I have all the boards for 32K words of core. I am missing one of the top 
connectors between a core board and the address driver next to it.

I have a few I/O cards in the machine : 

12531-60022 Buffered TTY Reg (2 off) looks to be current loop and RS232 serial
12551-6002   Relay Out Reg
12592-6001 +8 but Dup Reg (8 bit parallel for paper tape punch/reader?)
12554-60023 +16 bit Dup Reg (16 bit parallel?)
12566-60021 +True In/Out (another 16 bit parallel?)
13210-60004/6 Disc Interface 1/2 (7900 interface, 2 boards)
12539-60001 Time Base Gen (Heartbeat interrupt ?)
12590-6001 Plotter (I can find nothing about this board on the obvious sites).

Anyway, I have downloaded the appropriate manuals, but have some questions...

What is Current Transfer Logic, the machine seems to be full of such ICs?  Any data sheets,
etc out there?

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.

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...

Any information on that 'Plotter' board?

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 have taken the switch assembly apart (there is an exploded diagram in the IPB manual) and 
it seems to use a standard Ace 7 pin tubular lock. 

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

If not, I wonder if I could get a replacement lock and key? Or take the existing lock apart (looks
to be one pin to drill out to get it apart, at least the IBM 5170 lock comes apart like that) and
either get a key cut to suit the existing pinning, or re-pin it.

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?


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