Re: EDD + CARD

[Dick Sisco <rsisco@mchsi.com>]

On Fri, 26 Jul 2002 15:33:17 -0000, russotto@grace.speakeasy.net
(Matthew Russotto) wrote:

>In article <md61ku4rts0okshsusisv15ifgeeuv9g2r@4ax.com>,
>Dick Sisco  <dsisco11111@mchsi.com> wrote:
>>
>>But that is exactly why it works as a protection scheme.  After about
>>8-10 0 bits the standard Apple (or IBM) controller begins returning
>>random bits.
>
>Why does it do that?  A 0-bit is a lack of transition on the disk; while
>the controller may not be able to figure out how many non-transitions
>occurred, I don't see why it should start returning 1s. 

As it was explained to me, the circuitry in the disk controller turns
up its aplification(?) if it doesn't see transitions. It eventually
senses a transition when there really isn't one.   I can't swear that
that's an accurate description, but that was the way the instructor at
a disk duplicaton seminar explained it to me.  And it did seem to
work.