Re: Write .nib files back to disk

["Jayson Smith" <nospamratguyspambegone@nospamplease.bellsouth.ihatespam.net>]

Hello,
First of all, I don't know of a solution to your problem.  However, I'll try
to make you understand why the methods you're trying won't work.
First, you need to understand what a disk image is, and what a nibble image
is.  A disk image is 143360 bytes.  This file contains what you might call
the high-level representation of the contents of the disk.  For example, on
track 17, sector 0 of a disk image is the exact sequence of bytes a program
would receive when telling DOS to read track 17, sector 0 of the disk.
There are only the 256 bytes of actual data.  There are no checksum bytes or
other data which DOS uses to validate the sector.  On an emulator which uses
.dsk files, most likely every disk which is properly inserted is perfect.
Since there are no checksums, the emulator probably has to generate them to
satisfy DOS that the data is OK.
A nibble file, on the other hand, contains more data.  This type of file
contains the raw, low-level contents of the disk.  When DOS reads a sector,
what it actually gets from the drive itself is this low-level contents.
This data includes not only the 256 data bytes, but checksum and other data.
Any time you get an I/O error, that is because DOS is unable to validate the
data on the sector it is trying to read, because either the data itself or
the validation information has been corrupted.
The way many copy protection schemes work is to intentionally mess something
up about the disk.  This could be in one particular area, or the entire
disk.  But anyway, the point is that normal DOS can not read the disk, or at
least it doesn't think it can.  Something about the low-level data has been
messed up.  When a nibble file is converted to a .dsk file, all the checksum
data is eliminated so the disk appears to be perfect.  Therefore, when the
protected program checks to make sure it's legit, the check fails as the
disk looks perfect so it must be an illegally made copy.  Even if you use
nibble copiers on the disk image, they won't work for the simple reason that
the original disk they're copying from is, for all practical purposes, a
perfectly ordinary disk.  So the copies won't be any good either.  Even
converting the copies back to nibble files won't make them good since the
intentionally messed up information was lost in the original conversion and
cannot now be restored.
I found a program called nib2file for Prodos, but it only works one way,
converting a disk into a nibble image.  It can not convert a nibble image to
a real disk.
Hope this helps!
Jayson.

"amauget" <amauget@hotmail.com> wrote in message
news:418d7040$0$18478$8fcfb975@news.wanadoo.fr...
> Hi All !
>
> I'm currently trying to write .nib (protected) image files back to 5"1/4
> disks.
> I can't use the classic ADT solution that works only with .dsk files.
>
> I've read FAQs but unfortunately, don't find any method that works. Here
are
> the facts :
>
> First, I've tried to use convertors such as NIB2DSK.EXE. But the DSK files
> aren't working.
> Then, I've tried to copy the .nib to a .dsk using an emulator and various
> copy programs (Locksmith 5.0, Disk Muncher, CopyII+ 7.0, ...). All fail.
> Finaly, I've tried an interresting (but not working) solution :
> - load the .nib file into an emulator,
> - use SST (Saltine's Super Transcopy) to make 2 dsk files from one nib
file,
> - send the 2 dsk files (via ADTGS) to my Apple II GS
> - use SST once again to write the 2 DSK onto 1 disk.
> Once again, it fails.
>
> I'm stuck ! Have you got any clue before I'm going crazy ?
>
> Thanx
>
> Antony
>
>