Re: Hardware musings

[pausch@saaf.se (Paul Schlyter)]

In article <453f17d8$0$15690$5a62ac22@per-qv1-newsreader-01.iinet.net.au>,
Mark McDougall  <markm@vl.com.au> wrote:
>mdj wrote:
>
>> Not sure of how such things were done, but the PC drive is somewhat
>> more 'intelligent' that the Apple II unit, and essentially incapable of
>> writing 'bad' data by itself.
>> 
>> The Apple II's essentially 'soft' design means that much lower level
>> disk information is software visible. The upshot of this being that any
>> erroneous data that could be written by some as yet undiscovered disk
>> duplicator could be approximated by an actual Apple II drive.
>
>I seem to recall a rumour that the disk surface was damaged by a laser.
>
>Consider this: a protection scheme that does indeed permanently damage a
>known set of bytes on the disk surface. The software boots and then
>writes data to the area known to be 'bad'. Then it reads it back, and
>verifies that the data does *NOT* match what was written.
>
>This scheme could NOT be duplicated on any Apple II disk drive,
>regardless of the level of control over the drive itself.

It would indeed require a hardware modification of the Apple II
disk drive.  For instance the addition of a small neede which, under
software control, punched small holes in the disk.  That needle could
be mounted right beside the r/w head, and move along with it.

There will of course remain one problem: knowing *which* part of the
disk to damage physically.... ....finding that out would require
writing to, and reading back from, the original, to verify which parts
of the disk surface could not be reliably written to.  :-)

>Regards,
>
>-- 
>Mark McDougall, Engineer
>Virtual Logic Pty Ltd, <http://www.vl.com.au>
>21-25 King St, Rockdale, 2216
>Ph: +612-9599-3255 Fax: +612-9599-3266


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