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

[Robert Gault]

Fedor Steeman 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
>

Fedor,

You need to make sure about the disk structure. Very few Coco systems 
would have floppy drives that could access more than 42 or 43 tracks (of 
normal size) per side. Therefore it is very unlikely that these disks 
(assuming they are 5 1/4" disks) have 80 tracks per side.
The disks could be double sided 40 or, if copy protected, 80 tracks per 
side with each track 9 grans instead of 18.
If the disks are 3 1/2", then they could easily have 80 tracks per side.

Another question would be are these disks Disk Basic or OS-9? Accessing 
80 tracks with OS-9 just means changing the descriptor. With Disk Basic, 
you will need to override the ROM code so that higher track numbers are 
sent to the controller.