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





David Empson wrote:
"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:

At one point, one could buy the chips that upgraded a 13 sector card into a 16 sector card. I have a IIPlus that I got from an astronomy professor that was originally a 4K machine with 13 sector DOS. He had upgraded it, and I had the chips that had come from the controller card. Those chips were given to another AppleLinc member, and I trust he hasn't lost them....

Roy

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.



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