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Subject: Re: Creating a copy protected floppy
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Date: Fri, 15 Jul 2005 09:01:59 +0300
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Jack Klein wrote:
> I can't remember for sure if it was the original IBM PC, or the PC Jr,
> but one of them had a floppy disk drive with enough stroke on the head
> to be able to read and write 41 tracks instead of the normal 40 on a
> floppy.

My guess is both. PC-XT (which came afterwards) had a 'more-advanced' 
disk drive (or, that's what IBM said).

But, still much more later, there came 1.44MB drives, and into a 
1.44MB drive, you could easily push 82 tracks with 20 sectors a head, 
totalling 1.6MB (does this sound like some MS-W95 disks?), or even 
more, like 2M and its developer showed us (in source code also, if you 
read Spanish).

But, back to Jack and the 40-track disk:

> Some companies put their own custom, non-standard format and some data
> on that extra innermost track.  If an (unknowing) user used the
> standard diskcopy to try and make a program disk for a friend, only
> the normal 40 tracks were copied.
> 
> When the program started, it used either BIOS or direct hardware
> access to the disk controller to read the extra track.  If the disk
> was a copy, the data wasn't there and the program would not run.

> Then IBM changed suppliers for the disk drive in that particular
> computer, and the new disk drive did not have the extra stroke to read
> the 41st track...

<OT-or-is-it?>
Back in the 80's, a Finnish manufacturer named Nokia (who is now more 
known for their mobile phones) was manufacturing 8085-based PCs called 
MikroMikko. These PCs employed the (then) latest Intel FDC technology 
to access the floppy disks, for example. A genuine Nokia invention 
using the FDC was, instead of using the CP/M-standard 128-byte 
sectors, they used 512-byte ones. IOW, the sectors were formatted 512b 
(those who know NHCR, know what I'm talking about) which were then 
accessed in four pieces. Not so hard to imagine, that a floppy 
formatted in a MikroMikko would not be quite readable in another 
8085-PC. This way, however, they could have more sectors on a track 
than the standard CP/M way of 128bps would have allowed.

Also, their CP/M-PC was the first one I've seen where you could use 
both sides of a floppy (here, I may be wrong, though) without flipping 
it over.
</OT-or-is-it?>

Another funny remark: IBM first invented the "hole" to distinguish 
between 720k and 1.44M floppies; however, the only computers I ever 
saw that did not judge the disk using that "hole" as the indicator of 
its size, were all made by IBM...

> Wasn't is Lotus who used to use a laser to burn a hole at a particular
> spot on the program disk?

IIRC, some version of their spreadsheet program (1-2-3). Or, it could 
have been WP also. Certainly after CP/M anyway, for that I'm sure :)

-atl-
-- 
A multiverse is figments of its own creations