Re: Suggested ADT enhancement

[Rubywand <rubywand@swbell.net>]

Jayson Smith writes ...
> 
> Hi there,
> I have just figured out why some DOS disks I'm transferring via ADT won't
> boot on a real Apple.  It has to do with disk volume numbers.  Let's say you
> have a disk image with volume number 019.  Now let's say you've freshly
> formatted a brand new, just now unsealed blank disk.  You transfer the disk
> via ADT then try to boot it.  Only to find out that it won't boot.  What
> gives?  Well, the answer is that when you formatted the brand new disk, it
> was most likely assigned volume number 254.  This is the DOS 3.3 default.
> But this isn't just a handy number for reference, this number is also stored
> in every sector so that DOS can make sure it's dealing with the right
> volume.  So when you transferred disk volume 019, the DOS on that disk is
> expecting the disk in the drive to be 019 when it is in fact 254.  My
> proposed solution to the problem would require modifications to both parts
> of ADT.  When ADT sends a disk, it would check the VTOC to find out the
> volume number of that disk.  Then the Apple program would reformat the disk,
> or each sector as it copied it, to have the correct volume number.
> Jayson.


     The whole idea of having a Volume Number is one of those features which
looks so much like a bug that sometimes it's hard to tell the difference. For
sure, dealing with the result has cost untold hours of user time, such as when
transferring disks via ADT.

     Your solution is an interesting try; but, it would not work:

o- A .dsk file does not have to be a disk image of a DOS 3.3 diskette. It may
be an image of a ProDOS diskette (which has no VTOC) or of a diskette using
some other 16-sector DOS which may not use a VTOC or may place it in a
different location.

o- If there is a VTOC, there is no guarantee the VN there is the actual VN some
code will check for. For instance, some deprotected disks may have patches to
work correctly with the default DOS 3.3 VN but not make changes to the VTOC
which may show a different VN.



Rubywand