Re: Apple ][ plus 13 sector! Problems...

[dempson@actrix.gen.nz (David Empson)]

"Bill Garber" <willy46pa@comcast DOT net> wrote:

> Thank you David. I really must take some time
> and read through all these books. After all,
> I did buy them to learn from. What programs
> can I use to convert a 13 sector disk image to
> a real disk?

No idea.  I haven't done anything signficant with emulators.  I only use
the real thing. :)

> From what you wrote above the 16 sector controller should be
> able to still write one?

Yes.  The 16-sector controller (and the 13-sector one) can write
anything, even disk bytes which can't be read back by the same
controller: any 8-bit data pattern is possible, but if the written byte
doesn't follow the rules, it won't read back reliably (or at all).  You
can even write mistimed bytes, by waiting longer than 32 microseconds
between writes.  (I'm not sure what would happen if you waited less than
32 microseconds - probably get a partial byte followed by the next
byte.)

Copy protection techniques have been known to pull these sort of tricks,
and use other tricks such as timing measurement to determine whether the
disk has been written with the correct special rules.
-- 
David Empson
dempson@actrix.gen.nz