Re: Vista Support Software

["Michael J. Mahon" <mjmahon@aol.com>]

Steven Hirsch wrote:
> On 04/22/2012 11:23 PM, Michael J. Mahon wrote:
>
> > Steven Hirsch<snhirsch@gmail.com>  wrote:
> >
> > > On 04/22/2012 03:14 PM, Michael J. Mahon wrote:
> > >
> > > > Steven Hirsch<snhirsch@gmail.com>   wrote:
> > > >
> > > > > On 04/22/2012 11:39 AM, Steven Hirsch wrote:
> > > > >
> > > > > > To my great dismay, all the DOS 3.3 and Pascal driver support 
> > > > > > diskettes for my
> > > > > > Vista A800 8" drive controller are blown and unreadable.
> > > > > >
> > > > > > Does anyone have good copies of these that they wouldn't mind 
> > > > > > imaging?
> > > > >
> > > > >
> > > > > Quick update:  I was able to recover everything but the Pascal 
> > > > > driver by
> > > > > trying a couple of different Disk ][ units.  Unfortunately, nothing 
> > > > > was
> > > > > unable to read anything useful from the Pascal Attach diskette.  
> > > > > Only the
> > > > > first track is intact.  It may have always been that way for all I 
> > > > > know (never used it).
> > > > >
> > > > > So, if anyone can find the A800 Pascal 1.1 support - much appreciated!
> > > >
> > > >
> > > > Steven, try taking a look at the disk using Copy II Plus's hi-res disk
> > > > scan, under the bit copy option. That will quickly reveal which 
> > > > tracks are
> > > > formatted, and the extent of damage to formatting.
> > > >
> > > > I'd not expect any protection on a driver disk, but there may be some
> > > > damage.
> > > >
> > > > Also try a simple bit copy. It could recover a usable copy.  (I presume
> > > > you've already tried a sector copy--it can also yield a working disk.)
> > >
> > >
> > > It seems to be extensively damaged.  Would probably take a miracle to
> > > read anything off this cookie...
> >
> >
> > If this is a "published" diskette, it may simply have been written on a
> > drive out of alignment or off-speed. That's why visualizing the data 
> > with a
> > high-res scan and .25 track stepping can be quite helpful.
>
>
> Maybe I'm not smart enough to understand it, but it's unclear what Copy 
> II+ is trying to tell me about the diskette.
>
> I'll dig to see if I have any documentation for the program.

I presume that you've already tried different "known good" drives.
Obviously a dirty head, off-speed drive, or misaligned drive will
have problems with a properly recorded disk.

There are a host of ways of "fixing" "unreadable" disks--and
only a very small fraction of "unreadable" disks are actually
not able to be recovered.

If the problem is physical, this will often be revealed by slowly
turning the media while watching very carefully through the head
access hole on the bottom of the diskette sleeve.  Sometimes it's
a speck of dirt, sometimes mold, sometimes a small crease.  All of
these conditions can be remedied with careful work.

Sometimes, the disk sleeve has been pressed so that the media does
not turn freely, resulting in speed errors and therefore read errors.
This is easily fixed by running the edges of the sleeve against the
edge of a table while applying moderate pressure.  Careful to avoid
the notches, big and small, and the area right by the head access hole.

If the problem is with the data, the hi-res scan will show the
self-sync nibbles on each track, half-track, or quarter-track.  This
nicely flags the presence of "sectors"--or their absence.  Take a
look at a good disk to see what one should expect.  If the drive
used to write the diskette was misaligned, then there may be a "good"
pattern of sectors off by a quarter-track from the expected position.
If this is the case, I keep a "who cares" drive around that I can
put out of alignment to match the misaligned diskette and copy it
to a new disk in a properly aligned drive.

If the sectors are properly aligned radially, then using a nibble
editor to look at the sectors that won't read can sometimes reveal
a single nibble error, which, when fixed, will restore the sector.

It's always a good idea to start by trying to make a sector copy
of a bad disk, since the copy routine may retry enough times to
get the data.  Failing this, a bit copy of the disk should be done
so that the recovery operations can be done without risk to the
original disk.

If you wish, I'll be able to attempt a recovery of the disk
around July of this year.  I stress again that it is very unusual
for a properly stored disk in reasonable physical condition to
be unrecoverable.  Apple 5.25" diskettes use relatively "fat bits",
and are remarkably reliable.

-michael

NadaNet 3.1 for Apple II parallel computing!
Home page:  http://home.comcast.net/~mjmahon/

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