Re: GCR Encoding

[Eric Smith <eric-no-spam-for-me@brouhaha.com>]

sean weintz <strap@hanh-ct.org> writes:
> Cracked apple ii games for 4 years as a hobby, and never heard the term
> weak bit used. What ARE you talking about?

Weak bits are bits that are written with modified hardware in such a way
to make them difficult to read reliably.  Copy protection systems using
weak bits basically read a sector multiple times to make sure that it
reads correctly some minimum percentage of the time, and gets an error
some minimum percentage.

This was not a popular technique as it didn't tend to work reliably
on all systems, depending on the performance of the heads, read
amplifier, and AGC of any given drive.  I believe this was somewhat
more common on TRS-80 software than Apple II software, but I don't
have any hard evidence.

I'm not aware of any way to write them using a stock Disk II controller.