Re: DSK to NIB Instruction

["josephoswaldgg@hotmail.com" <josephoswald@gmail.com>]

Ed Eastman wrote:
> Linards Ticmanis wrote:
>  > How do the emulators do it when using .nib images? Given the fact that
>  > there are a lot of .nib images out there that actually do work on an
>  > emulator, it seems the emulators somehow are able to deal with the sync
>  > issue?
>
> The sync issue is irrelevant to emulators.  You only need the sync bytes
> when reading a 'soft sectored' diskette on a real diskette drive.

Irrelevant EXCEPT for what you say afterwards:

> To get true emulation of the hardware to support highly protected
> diskettes, it would need to progress not only down to the bit level, but
> to the track to track seek timing level as well.
>
> While not impossible, it is probably easier to deprotect, normalize and
> or crack the original programs to allow them to work in the emulator.

What, in principle, requires the preservation of sync bits (and
track-to-track synchronization) is the copy-protection routines that
probe in ways that distinguish sync bytes from non-sync bytes.

The track-to-track timing issue is not so hard; if the NIB file
represents synchronized bytes, the emulator only has to track the 300
rpm rotation of the drive in terms of nibbles-per-minute, as the
stepper control code executes according to 6502 cycle timing. The NIB
production code on the Apple II would have to use the standard "sync
track" copying option with compatible timing.

That said, the most aggressive copy-protection methods (with special
disk media, non-standard write pulses etc.) could be emulated only by
elaborate, almost customized, emulation programs. Where to draw the
line between requiring deprotection or normalizing and completely
faithful emulation is a matter for the emulator writers to figure out.

One of my own pet projects is to get an ADT-like program to transfer
nibble-counted tracks for programs like Flight Simulator which cram
"extra-long" tracks onto the disk. Then, I'd use my own custom
NIB-processing tools to normalize the disk as much as possible for
emulation.