Re: Hardware musings

[Mark McDougall <markm@vl.com.au>]

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.

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