On 23 jan, 23:45, "Michael J. Mahon"  wrote:
> Andy McFadden wrote:
> > In comp.sys.apple2 e...{at}neilsonhart.com wrote:
> >> I believe a straight Nibble copy will get you pristine backups of
> >> Ultima I-IV.
>
> > IIRC, Ultima I just used altered address / data fields, but Ultima II
> > added some sort of secondary check (nibble count?) which .nib won't handle.
>

Ultima I alters the address and data fields.
Ultima II adds a nibble count.
Ultima III alters the address and data fields and uses false opcodes.
Ultima IV adds a nibble check and alters the address fields depending
on the filename (see. http://www.hackzapple.com/phpBB2/viewtopic.php?t=46)
Ultima V adds 16 to the sector number ;-)

> >> As far as I know, no other emulator supports the .v2d format which is
> >> a shame because it's an open standard.
>
> > Where is this open standard published?  Google didn't turn up much, but
> > perhaps I was searching for the wrong things.  I'm curious to see how
> > different sync-byte widths are represented.  (I'd also like to see an
> > uncracked "spiradisc" Frogger image boot.)
>
> Right!
>
> Adding support for quarter-track disks will only incrementally
> increase the number of protected disks that can be represented.
> Many protections lie outside the realm of quarter-tracked .nib
> representation, even if the tracks are "synced".
>
> It would be very helpful if a "census" of disks and the protections
> they rely on were available, so that the cost/benefit ratio for
> incremental additions of capability could be quantitatively assessed.
>
> -michael
> (cut cut)

Nearly 100% of Electronic Arts programs use a sort of spiralling on
three tracks at the beginning of a disk: the track-arcing.
Sirius programs were put on half tracks only.
Hold-Up by Infogrames uses spiralling on the whole disk, a curiosity.

The number of programs that use .25 tracks is close to 0 compared to
the quantity of Apple II programs.

antoine
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