Dobbertin Memory Expansion

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Dobbertin Logo

A memory expansion by the German company Dobbertin.

The Dobbertin memory expansions are compatible to the memory expansions by dk'tronics. The memory expansion came in two versions. A version with only the memory expansion, and a version with two sockets for additional rom software.

Technical Specifications

Could take memory configurations of Dram types 4164 to 41256, thus making memory configurations between 64Kb and 512Kb possible.

Optional two rom sockets. Each socket could be manually configured for rom 1-15

I/O port decoding is the same as Dk'tronics.

A15=0 with all other address bits can be any value. (Use 7fxx for compatibility)

Dobbertin supports all ram configs (c4-ff) as expected.

But, on a 464 with ROMs enabled and config 3 (c3 etc) is chosen we see:

&0000-&3fff: base ram &0000-&3fff
&4000-&7fff: upper rom
&8000-&bfff: base ram &8000-&cfff
&c000-&ffff: upper rom


Dobbertin supplied RDOS as a optional ROM to use the memory expansion as RAM disc with 444 KB free. They also supplied CP/M 2.2 and Plus with full support of the RAM disc. Other software using this RAM expansion: Discology, FutureOS and ParaDOS. Arnor software like Prowort and Maxam II also support the usage of the RAM disc.