Re: .DSK Image does not work on real machine, but, works fine in an Emulator

[Rubywand <rubywand@swbell.net>]

olcott writes ...
> 
> Rubywand wrote:
> 
> > olcott writes ...
> > >
> > > The solution was to make sure that the target
> > > disk was fully INITialized. After I ran INIT
> > > on the disk, then copied the image, it worked
> > > fine.
> >
> >      Yes. The ADT (v1.22 readme.txt) directions specify " THE
> > DISK IN SLOT 6 DRIVE 1 MUST BE 16-SECTOR FORMATTED." Probably,
> > this should be expanded to include suggestions of ways to
> > format the disk-- e.g. INITing the disk or using a util like
> > Copy II+ to format it.
> >
> 
> That's the problem. Formatting is not enough.
> I formatted it using a version of Prodos, and
> this did not work. I am guessing that the
> boot sector is not copied in a disk image.
> With other disk image files, they are byte-for-byte
> copies of EVERYTHING that is on the disk.
> Apparently ADT .DSK  image files EXCLUDE
> the boot sector.
>

     It may seem that way; but, as Simon notes, it isn't. ADT copies a complete
143,360 byte image. In terms of 35-track 16 sectors/track content, 143,360
bytes is the 'whole ball of wax'. You get the boot sector.

 ....

> >      Anyway, it's a good idea to INIT HELLO target
> > diskettes for ADT transfers.
> >
> 
> MOre than a good idea, I think that it is required.
> 
 ....

     When it comes to transferring a disk image to diskette, the main
difference between a target formatted via INIT HELLO under DOS 3.3 (ProntoDOS,
EsDOS, etc.) and some other diskette is that you know the INITed diskette has
the right format and that its Volume Number is the default-- i.e. it is 254.

     If you use a target diskette which you know is 'a regular DOS 3.3
diskette' that works fine for booting and for saving files or a diskette which
has been formatted for ProDOS, it is fair to say that you know it has the right
format-- 35 tracks, 16 256-byte sectors per track, etc.. (It may have 36
16-sector tracks; but, that's okay. It has at least 35.)

     You may not know anything about the diskette's Volume Number. An old DOS
3.3 diskette may have some special Volume Number. If the diskette is formatted
for ProDOS, it probably has a Volume Number set to 1 (the usual default for a
ProDOS formatted diskette).

     Standard .dsk (.do, .po) disk images do not preserve Volume Number because
it is information which is not reliably included in the contents. Volume Number
is embedded in the format (e.g. address headers, etc. which prefix each
sector's content).  Emulator programs generally assume/assign a Volume Number
of 254 when handling DOS 3.3 images.

     In most cases, the Volume numbering of a disk image does not matter
because, to work on an emulator, it usually _can_ _not_ matter. Consequently,
the Volume Number of the target diskette for a transfer usually does not
matter.

     One of the few possible exceptions to the above would be a DOS 3.3 disk
image which starts a program which insists that Volume Number be 254. Such an
image would work fine on an emu. It would not work on a real Apple II after
being transferred to a diskette with some other Volume Number.

     Evidently, the particular image you transferred is one of the few special
cases.

     The FAQs does strongly recommend using INIT HELLO and tells why. (See the
File Utils page at http://home.swbell.net/rubywand/Csa2FLUTILS.html#006 .) 
Very likely, this information should be emphasized in ADT documentation.



Rubywand