Memory options for an HP 1000 (HP 21MX / 2112A)

J. David Bryan jdbryan at
Fri May 22 23:55:34 CDT 2015

On Thursday, May 21, 2015 at 23:45, Marc Verdiell wrote:

> I took a quick look inside to confirm
> - there is a DCPC and a MEM protect card

Good.  (To avoid confusion with the Memory Expansion Module, the latter 
card is usually designated MP or Memory Protect.)

> - No MEM card in slot 112


> - Under the processor board there is a screwed on card, which seems to
> have ROM on it. Microcode I presume, but I don't know if that's the one
> you were talking about.

One such card is present in all M-Series systems and contains the microcode 
for the base set of instructions.  If there's DMS or FFP/DMS firmware 
present, it would be on a second such card, mounted next to and connected 
via an edge-card connector socket to the base set card.

It sounds as though DMS is not present.

> The IO cards and the paper tape reader / punch that came with it
> suggest that it was configured with a paper tape reader, a paper tape
> punch, a mag tape and a TTY interface. A plausible story is that this
> was an early machine setup for paper tape and TTY and didn't have
> extended memory. 

A reasonable assumption.

Did it come with any software on paper tape (or mag tape)?

> So I might be in the hunt for the cards or alternate solutions you
> mentioned.

I'd suggest that the question to answer first is whether you want to expend 
the effort and expense to gather the moderate amount of additional hardware 
necessary to run one of the more advanced disc-based OS versions that can 
use DMS.  Note that the design of the memory mapping hardware in the 1000 
requires explicit software support (i.e., programming of the DMS hardware) 
in order to use more than 32KW of memory.  Earlier OSes that did not 
support DMS will simply ignore all memory in the machine over 32K, even 
when DMS is present.

With the hardware you have, you can run a paper-tape based OS, such as BCS 
(the Basic Control System) in 24K.  BCS is fairly primitive, but it does 
offer an assembler, FORTRAN IV, and ALGOL compilers, and paper-tape BASIC 
interpreters were also available (from the user contributed library).

The hardware requirements for running the disc-based RTEs are listed on 
these HP Computer Museum pages:

                                      -- Dave

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