Re: Using both sides of DS DD disks

[mjmahon@aol.com (Michael J. Mahon)]

Frank Townsend wrote:

>"Dave Althoff Jr" <dalloff@gcfn.org> wrote in message
>news:apsqvl$ite$1@acme.gcfn.org...
>> Greg Weston (gwestonREMOVE@CAPSattbi.com) wrote:
>>
>> : It's worth noting at this point that Apple II 5.25" drives write on the
>> : "wrong" side. If you have a single-sided disk, the label side is the
>> : one that was tested, but Apple II drives wrote to the bottom of an
>> : inserted floppy.
>>
>> I wondered when someone would bring this up...
>>
>> It made for some interesting dual-format disks.  Somewhere I have a
>> Hallmark animated greeting card that was sold to work on either an Apple
>> ][ or on an Atari 800.  Either way, you stick the disk in the same way
>> because Apple's R/W head is on the bottom but Atari's R/W head was on top.
>
>Would this explain the "dual format" Trackstar 128 v6.2 5.25 floppy?
>
>Supposedly, part of it can be read by a PC and part of it can only be read
>by an Apple ][ already booted into DOS 3.3, all done without turning the
>disk over.
>
>Do PC drives R/W from the top also?

PC drives are two-sided--both sides of the diskette are recorded.

The dual-format TrackStar diskette is partially formatted as an MS-DOS
disk (up to the middle, which is where an Apple DOS 3.3 disk has its
catalog).  Then from the "catalog" track in to the center, it is formatted
as an Apple DOS 3.3 disk.

Such a disk is a thorough hybrid creature, and almost impossible to
duplicate on either a PC or an Apple.  Both computers are required,
together with a patched Apple formatting routine, to do the job.  (Or
manually-controlled partial disk copy routines, running on each
computer, could be used, as well.)

In any case, the typical disk image formats for _either_ system
will not be effective in capturing the information on this unique disk.

It would not be difficult, however, to use a PC to copy all the PC
files off the disk, and an Apple to copy all the Apple files to a 
different disk.  The two disks produced in this way would both
be easy to archive and to copy (with their respective systems).

-michael

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