On Sun, Oct 1, 2023 at 8:38 AM Wouter de Waal via cctalk
<cctalk@classiccmp.org> wrote:
>
> Hi all
>
> I re-discovered some eurocards I found in a box at a swapmeet long ago.
>
> It looks like a complete 8085 system. Lots of RAM, 2K EPROM, I/O, FDC.
>
> The strange thing is that the EPROM is mapped at F800, the code in there
> looks like 8085 code, and looks like it wants to live at F800. And there's
> RAM at 0000.

It might have run CP/M (which will run on an 8080, and therefore on an
8085). That needs RAM at location 0000 [1].

If the EPROM is mapped to F800 only (some machines mapped it to 0000
as well after a reset, this image was disabled after the processor
jumped to F800 or wherever) then there might be  a bit of logic to
force a jump instruction onto the  data bus after a reset to get the
processor to run the code in the EPROM.

[1] For the pedants, there were 'relocated versions of CP/M that could
run on machines like an unmodified TRS-80 model 1 with ROM at location
0. These versions needed special relocated versions of all the
application software and were generally pretty useless.

-tony

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