HP2100A luser questions

Brent Hilpert hilpert at cs.ubc.ca
Thu Nov 20 23:49:33 CST 2014

On 2014-Nov-19, at 1:43 PM, tony duell 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.


> 12531-60022 Buffered TTY Reg (2 off) looks to be current loop and RS232 serial

Those should be 12531C's, they should have 225.28 KHz crystals, intended for 110 baud operation.
Changing the crystal to 307.2 KHz should change it to a 12531D, for the standard baud rate series, if desired.
These are the common console-device interface.

Some info:

> 12592-6001 +8 but Dup Reg (8 bit parallel for paper tape punch/reader?)



> 12539-60001 Time Base Gen (Heartbeat interrupt ?)



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

The 2116,15,14 and 2100 used Fairchild CTuL, along with some TTL.

The family name is actually "Complementary Transistor MicroLogic".

It's an early (mid-1960s) IC family, similar to ECL in that it is a current-mode / current-switching / non-saturating logic implementation, but involving PNP & NPN transistors in the construction (hence the complementary).

When I was first obtained my 2116C ~15 years ago, I was fortunate to already have some Fairchild catalogs that discuss the family.
Some info:

However, I was just looking at the Fairchild catalog now on bitsavers which Eric mentioned, and it has more complete info.

> 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.

I have run across mention of the two connectors and the spacing distinction in some manual but don't recall where off the top of my head.
It's one of those 'why did they do it that way' questions: from what I see, if they had just ordered all the board pairs the same rather than putting them in mirror image, they wouldn't have needed two different top connectors.


> 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?

Aside from blinkenlight programs, in the not-to-distant future there should be a stand-alone version of HP BASIC available. A friend and I are working on assembling it from source. (There are probably old binaries out there somewhere but I haven't obtained one).

I believe HP-IPL would run on a machine such as you have, it's a new (2000-era) Forth-based system for the 2100 series, however I have not used it.

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