In article <20020725155113.09099.00000672@mb-ch.aol.com>,
Michael J. Mahon <mjmahon@aol.com> wrote:

>If the presence of a non-standard number of 0 bits were not detectable
>by a Disk ][ controller, this so-called "bit stuffing" scheme could not
>be verified to be present, negating its usefulness as a disk "signature"
>technique.

There's a couple of common things that were done without trying to
verify the non-standard self-sync bits directly, such as sticking in
some non-self-sync FFs where there would normally be self-sync FFs.  If
you do it right, you can make a normal "nybble copy" (which will assume
they are all self sync) write too many bits and corrupt the disk, or at
least shrink one of the gaps to a detectably smaller length. 

-- 
Matthew T. Russotto                                mrussotto@speakeasy.net
===== 
Every time you buy a CD, a programmer is kicked in the teeth.
Every time you buy or rent a DVD, a programmer is kicked where it counts.
Every time they kick a programmer, 1000 users are kicked too, and harder.
A proposed US law called the CBDTPA would ban the PC as we know it. 
This is not a joke, not an exaggeration.  This is real.
http://www.cryptome.org/broadbandits.htm