[Coco] Strange.... two 40 track disks on one 80 track disk?

[Arthur Flexser]

I'm sure the Disk Basic ROM could be patched to do this, but I think it
would require quite a bit more than just a couple of pokes.  For example,
the locations of the directory and GAT are probably hard-coded to Track 17
in a lot of places.  But I agree with Robert that you need to be sure of the
structure--it is more likely that the missing files are on the back side of
the disks than on tracks 40-79.  (Could the disks be "flippies" that need to
be inserted into the drive upside down to see the other files?)

Assuming the files are all on the front side, my guess is that they were
placed there by an archiving program that came with a recovery program to
transfer the upper half of the disk's files back to tracks 0-39 (or maybe
0-34, if it follows standard RSDOS structure) of a second disk.  You might
want to look around for that program among the disks you acquired.  In any
case, it shouldn't be difficult to write a simple Basic program that
transfers the files back to the normal part of a second disk, either using
DSKI$ and DSKO$ (if I'm remembering the names correctly), or by just poking
in the appropriate DSKCON parameters and executing DSKCON multiple times.
Not as elegant as patching the ROMs, but a lot simpler to get working
properly.
Art


On Sat, Oct 31, 2009 at 4:50 PM, Fedor Steeman <petrander at gmail.com> wrote:

> Hi,
>
> Some time ago I acquired this huge collection of diskettes that were part
> of
> a user group's CoCo software library. A lot of these are backups of backups
> so there is bound to be a lot of stuff I will be able to recover.
>
> There are a large number of diskettes that seem to contain a backup of two
> 40 tracks diskettes on one side of an assumed 80 track diskette.
>
> However, I can only access the first diskette of each of these backup
> floppies. I know because some of them have their contents listed on the
> envelope (or whatever you called the paper bag the diskette is in).
>
> I have a drive that can be switched from 80 to 40 tracks but that made no
> difference.
>
> Is there some way in HDB DOS that I am using (or RSDOS for that matter)
> that
> would enable access to the other 40 tracks and thus the other diskette
> backup?
>
> Thanks for any help...
>
> Cheers,
> Fedor
>
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