Re: WildCard By Central Point Question

[Andy McFadden <fadden@fadden.com>]

Bryan Parkoff <BParkoff@satx.rr.com> wrote:
>     I understand that it is SpiraDisc.  How does SpiraDisc block Apple II
> users from reading data using nibble editor.  Is it true that we have to
> read 6502 code (assembler) from the track 0 sector 0 before we can
> understand what 6502 code (assembler) manipulate with the disk?

It uses quarter-tracking.  Apple II 5.25" disk drive controllers give
software direct control over the stepper motor, so you can do funky things
like freeze the head partway between tracks.  This didn't work on some
3rd-party 5.25" drives, causing certain people to lend certain other
people copies of Frogger, which subsequently got cracked, written up,
and submitted to COMPUTIST.

(Try that today and the DMCA police would have you in jail.)

Anyway.  You need to get the data from the tracks *and* have it
properly synchronized, so that when they move from track 0 to track 0.25
the next set of data is right under the read head.  If the data doesn't
show up quickly enough, they know it's a copy and the boot fails.

Copying is tricky because there's a lot of "leakage" from adjacent
half-tracks.  If you tried to write the disc as a series of tracks,
you'd be stepping on the half-tracks and quarter-tracks to either side.
Which might work out okay if you could get the synchronization just right.

Spiradisc was a thing of beauty.  I wish I could find my write-up of
the Maze Craze disk, which had a disk-present check that Frogger didn't.
I also truncated the Frogger write-up severely because I just referred
to the Maze Craze discussion (i.e. there's not a lot of details about
the protection itself).  Sadly, the Maze Craze "softkey" was rejected
for publication, so if I can't find it then it probably doesn't exist.

Among their many tricks was an XOR of the copy protection code, so you
can't find it by scanning through the disk or through memory unless you NMI
right when the protection check is happening.  You *must* boot trace the
disk, stopping it at various points.  They used every trick in the book.
In the end it didn't save them. :-)

>     Where can I obtain the information like CompuList #52?  I did check
> www.apple2.org.za, but it does not provide enough information.

There were scans of COMPUTIST issues on a web site, but I don't know if
it's still up (or what the URL was).

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