Re: EDD + CARD

[Stephen Shaw <bottrawler@junkbuster.zzn.com>]

On 31 Jul 2002 23:59:44 GMT, Michael J. Mahon wrote:

> Stephen Shaw suggested:
>
>>On Fri, 26 Jul 2002 17:18:42 GMT, Dick Sisco wrote:
>>
>>> 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.
>>
>>Ok. if the above is the case then it is quite easy to back door into the data
>>stream with an RS232 converter to a PC/Mac/Linux box and read the binary
data,
>>sort out what copy protection is being used and nullify it.
>
> With the bit stream at 250,000 bits per second, that seems unlikely.

If Apple used 74 series chips in the drives in those days a design should be
possible using 74 series chips now.

>
> -michael
>
> Check out 8-bit Apple sound that will amaze you on my
> Home page:  http://members.aol.com/MJMahon/

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