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

Marc Verdiell marc.verdiell at
Wed May 20 01:12:23 CDT 2015

Thanks, very useful info, and the manual is indeed what I was missing. But
now where to find the DMS, with two cards in particular, that's not going
easy to find both that match...

>> ...the recently posted IO manual says it can support ... up to
>> 1.28M. 

>From: "J. David Bryan" <jdbryan at>
>That's correct, although the machine must be equipped with the Dynamic 
>Mapping System (DMS) in order to access more than 32KW.  For the 2112, DMS 
>is product number 12976A.  It consists of a card (the HP 12731A Memory 
>Expansion Module) that plugs into slot 112 in the front card cage) and 
>another card that contains microcode that implements the DMS instructions; 
>the latter mounts to the main CPU board at the bottom of the chassis...
>The "Standard Performance Memory
>Systems Installation and Service Manual" (5955-4310 April 1979) details the

>requirements; it's available from Bitsavers in the "1000" subdirectory.
> -- Dave

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