Date   : Tue, 29 Apr 2003 22:44:58 +0200
From   : John Kortink <kortink@...>
Subject: Re: BBC Micro Games Copy Protection

On Tue, 29 Apr 2003 07:48:53 -0700, Angus Duggan wrote:

>John Kortink writes:
>>
>>I think the Elite disc protection was based on 8271-specific tricks,
>>which would explain the problems running it on the Master. In fact I
>>doubt there have been Beeb game disc protections that did not assume
>>a 8271 was present in the machine.
>
>Correct. It was a dual 80/40 format disc, it contained code in the first
>track which worked out if the drive was 80 or 40 track, and
double-stepped 80
>track discs. The code was very 8271 dependent, it had to mess around
with the
>track register when double-stepping to convince the 8271 that it was
really
>at track 39 when it had stepped to track 78.

Ah yes, now I remember, Acheton used the same tricks. My
original Acheton discs were pretty flakey (the floppies
must have been sub standard, even on the first few runs
the drive sometimes had trouble reading the inner or
outer tracks, which I can't remember). By the time the
floppies got really erratic I'd already removed the
protection so I could (thankfully) continue to run the
game.


John Kortink