Re: Dark Crystal and Time Zone

[Tempest <tempest@atariprotos.com>]

On Jan 19, 8:30 pm, Linards Ticmanis <ticma...@gmx.de> wrote:
> On 01/19/2011 04:16 PM, magnusfalkirk wrote:
>
> > Has ANYONE EVER successfully used SST to change a .NIB file back into
> > a REAL Apple II disk? I read the threads you linked to Dave and in the
> > end both of them said that it couldn't be done. As an experiment I
> > might just try using SST to copy a disk, say the Owner/General Manager
> > disk for MicroLeague Baseball, to 2 disks and then try rewriting it
> > back to a real disk to see if it can be done at all.
>
> Usually it doesn't work. NIB is an ancient format, older than DSK as far
> as I know, and, in hindsight, not terribly well thought-out.
>
> NIBs have longer tracks than any real Apple drive, to make sure
> everything fits even if the disk uses slightly shorter-than-normal bits
> or the drive is spinning too slowly. Because of this the beginnings and
> the ends of tracks will have varying amounts of overlap when a NIB is
> used to store a real disk. Unfortunately, NIB does not store the
> original track lengths anywhere, and does not mark where overlap begins
> and ends. Since areas of unused data won't be a perfect match between
> the overlapping sections (although used sections will be), finding the
> beginning and end of overlap takes some head scratching.
>
> Also on a real disk you have to start and stop writing at some point of
> the track and the bytes directly around that spot won't come out right
> on reading, because the disk doesn't spin so evenly as to guarantee
> hitting the exact same spot after what is supposed to be one whole
> revolution. So you have to make sure that spot is in a gap (unused part
> of the track), preferably in the largest gap; and there's nothing in the
> NIB format that tells you where in the track there are gaps and where
> there is actual game data.
>
> Thirdly the Apple needs to make a difference between self-sync bytes and
> normal bytes during the writing of a disk, otherwise you'll either get
> framing errors on reading (when you're not using self-sync bytes where
> you need them) or the data won't fit (when you're using too many
> self-sync bytes, which take up a bit more space on the disk surface).
> However the self-sync bytes and normal bytes come out the same during a
> normal disk read (you need special reading routines to tell the
> difference and even then the detection isn't completely reliable).
> Emulators (all that I know of) feed the emulated floppy controller one
> byte at a time, not one bit at a time as a real drive does, thus framing
> errors cannot occur in an emulator; and consequentially, NIB, as an
> emulator format, does not store the difference between normal and
> self-sync bytes at all.
>
> So the only way to get a NIB back onto a real floppy without actually
> cracking the game is to take a look at your NIB with e.g. a hex editor
> and find out what's going on - where tracks and sectors start, where
> overlap begins and ends, which bytes are probably self-sync etc. Then
> you can rearrange data so the largest gap is at the beginning, and mark
> likely self-sync bytes as such. Then you can use a relatively simple
> assembly language routine (which can be found in either Beyond Apple DOS
> or Beyond Apple ProDOS, I don't remember which) to write the disk one
> whole track at a time. I once put together a small program in C (cc65
> compiler) as a front-end for that assembly code, which I could send to
> interested people. However it won't do the NIB analysis described above,
> only the writing once the NIB has been pre-edited. In fine, let's hope
> KryoFlux gets disk write support soon, that should be the beginning of
> the end of this kind of trouble, at least for those people who own one
> (i.e. *ME* Bwahahahahahahaaaaaaaaaa.....)
>
> (Maybe I could make some money writing novels, or sermons. NOT. ;-)
>
> --
> Linards Ticmanis

Wow I didn't realize that it was that complex.  I'm surprised someone
didn't crack it back in the day since it was a sierra product, but I
suppose it wasn't a very popular game (I hadn't heard of it until a
few years ago).  Shame it's so expensive the two times a year it shows
up on ebay.  Maybe someone will crack it eventually.

Tempest