On Wed, Apr 15, 2009 at 3:42 AM, Anders Carlsson
<anders.carlsson@sfks.se> wrote:
> Ruud Baltissen wrote:
>
>> we can replace the MFM-drive by any drive we like:
>
> Honestly though, aren't 90X0 drives mostly collectable?

Sure, but the 90X0 drives are also repairable and somewhat modular, so
for me, at least, fixing a broken DOS board is something obvious to
do.  If I had a dead drive or a dead "middle board", I'd more
seriously consider either a more modern MFM drive (like an ST225) or
some way to hang a drive or drive emulator (FlashROM) off of the SASI
port so that the DOS board _thinks_ there's a drive out there.

I'm not one to have a box just to look at - I want to run it if it
works and fix it if it's broke.  I know there are those out there who
are more interested in a "complete" system because of how it looks.  I
am much more in the "use and repair as necessary" group.  That being
said, I probably wouldn't toss out an old TM602S or TM603S even if I
did replace it for use with something more modern (even an ST225).

> For
> practical purposes of a storage device, I'm sure you can build something
> that is both smaller, lighter and more durable from almost scratch.

Sure.  Since there's virtually no software that depends on DOS3.0 REL
files, there's nothing particularly magical about the implementation
of CBM DOS on the 90x0.  One could design an entirely new IEEE-based
storage device (and someone probably should), but since I already have
a couple of D90x0 drives sitting around and because the IEEE hardware
and firmware is done and known to be working on the DOS board, I
always attacked the problem from the point of view of putting
something different on the far side of the DOS board than the "middle
board" and Tandon disk (especially since Tandons are odd and rare and
expensive).

I am not in a position to be designing an IEEE storage device from
scratch, but if such a project comes around, I'd be happy to help
debug and use it.  The one thing that I'd want it to do is to support
either floppy images (so U1/U2 commands work on the contents of the
image) or have a way for an application to seek to an arbitrary
position in a file and read a block.  This is to support a virtual
memory scheme for Infocom games.  I have it working on floppy-based
games (i.e. - just as Infocom did for the C-64), but am unable to
migrate that to the D90x0.  Some/most of the Flash-based IEC drive
emulators that I've seen will let you mount a partition that's a .d64
file, which would completely suffice.

-ethan

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