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Re: Hardware musings

mdj wrote:

Michael J. Mahon wrote:



I never went wild with Copy II Plus' "automatic" mode, but I
seldom found that it worked for the disks I tried.  I therefore
have a very poor opinion about its quality.



I had good success with it, although it tended to be a bit touchy when
copying disks that used quarter tracks, and I always did drive 2 ->
drive 1 copies in this case.

I'm mainly suggesting that it it contains a relatively reliable bank of
information regarding used tracks on a disk - I'd venture good enough
in most cases for image pruning.


But, again, this would only be a space optimization, and introduces
the possibility of losing needed data.

Best to capture *everything*, from track 0 to track 39 in quarter-track
intervals, synced to t0,s0, and with "soft" nibbles marked.  Of course,
one must capture the length of nibbles, too: 8-, 9-, 10-bit lengths, at
least.  And the write-protect status.

Can anyone think of any other property of a disk that can be sensed
with a Disk ][ mechanism?

There is the potential for writing a track with ambiguous nibble sync,
in the sense that it could be read with nibbles synced in more than one
way.  I don't know of any program that uses such a technique, but it is
possible.  This would be a special case of "soft" nibbles, since no
noise is involved.


The image would implicitly document the protection used, and as a
result pare down the data captured to a bare minimum. Putting the image
back on disk then becomes more practicable.



It'd certainly be easy enough to have an emulator log what track
positions were actually used.


Exactly.  Then the only problem is making sure that the program has
been sufficiently put through its states that it has actually accessed
all the data that it could potentially access.


I have a feeling the disks that are going to be the nastiest are the
ones that appear unprotected, right up until they stop and some unusual
point. Often it's a case of data on track $23, or a sector epilogue
hack. When it's not one of those, it get's really interesting :-)


I agree--the trickiest protections are those that don't appear to
be there at all until long after the copy was made.


Just having a complete set of tracks, nibblized and synchronised as you
suggest, plus running them for a while through an emulator should give
the list of tracks most likely to recreate the disk successfully. Given
the relatively small amount of data by todays standards, it's probably
reasonable just to proceed as you suggest.



That's true. I'd like to get a feel for what software Copy II Plus
can't copy... Some of the later 18 sector titles might fit that
category, for instance Prince Of Persia


For one thing, there aren't that many entries in the latest parm
files compared to the total number of disks...



True. OK, so what do we need? An Apple II hosted imaging tool, plus one
of the popular emulators modified to load the image. That's enough to
get started, assuming a supply of willing participants with a
reasonable collection of copy protected software :-)


Yes, that would make a good start.

Without emulator and tool support, any new image format is doomed.
(Would you be on board with any of this, Andy?  BTW, I'd be very
interested in your thoughts...  ;-)

-michael

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