I am coding programms to run on a Dragon 64 and the module Dragon-MSX2+ by John Whitworth
As I am streaming data from a CoCo-SDC, my setup consists right now of an "oojamaflip" (by John Withworth) so that the CoCo-SDC
sits inside the Dragon case and then the MSX2+ module in the expansion port. That way both modules are parallel connected.
Well, if I do start with DosPlus50 or any Dragon Data DDOS 1.x, as soon as I access the SDC, for instance with DIR or LOAD, the result
uses to be garbage characters on the screen and most of the time the computer hangs and needs reset or power cycling
![Sad :-(](./images/smilies/icon_e_sad.gif)
Much to our surprise, if we do use SuperDosE8 or Eurohard DOS4.2 everything works flawlessly! How come does this work?
Another chance is modifying the setup and add a multiport, for instance the mini-MPI by Ed Snider. This simple change makes
all of the disk accesses work with no issues no matter the DOS we have started with.
So the problem seems to have two solutions. One software just changing the DOS, this demonstrates that some DOS versions behave
very differently from the others. But cannot tell what is that difference that helps just a few versions.
But as the fact of adding the MPI solves the problem too, it seems to point to a hardware problem too. Maybe some shared pins with
oojamaflip that now are isolated by the MPI are the responsible for the CoCo-SDC missbehaviour, but which ones?
I am attaching here the unassembled source file for SuperDosE6, made by Phill Harvey-Smith and the unassembled DosPlus5.0 (by Sixxie). I have added the Tandy MPI schematics so that any hardware guru could have a look at it and most probably will discover the problem when it is
not in the setup.
Any hint or idea about any reason that explains the way the two solutions do work will be highly appreciated.
Thanks beforehand
cheers
pere