[Coco] CocoSDC won't stay off

[Darren A]

On Wed, Dec 3, 2014 at 10:05 AM, John Goerzen wrote:

> ...

but now the plot thickens.
>
> So I have a second CoCo on hand now (see the thread about the mystery
> side-switches).  However, on this one, BACKUP 0 TO 1 DOES work.  D19.BIN
> and
> such still do not (it always seems to flip DRIVE 0 to ON even if I had
> previously said DRIVE 0, OFF).
>

Okay, so there is an issue with your original CoCo 2. It still may be the
CPU, a flakey cartridge connector or something else entirely. The symptoms
defy any explanation I can think of.

As far as D19.BIN, I'm afraid that is simply a matter of the software being
incompatible with SDC-DOS. In order to support multiple controllers (SDC
and Floppy), a program must utilize the ROM code for accessing the disk. I
assume D19 is talking directly to the hardware and not giving SDC-DOS a
chance to intervene and switch the MPI slots between the two.

Darren