Date   : Tue, 29 Apr 2003 11:55:33 +0200
From   : John Kortink <kortink@...>
Subject: Re: BBC Micro Games Copy Protection

On Tue, 29 Apr 2003 09:35:46 +0100, Richard Talbot-Watkins wrote:

>The original Acornsoft disc version of Elite didn't run on a Master.  It
>didn't even get as far as the "Saturn made out of dots" screen; instead
it
>just thrashed the disc drive head repeatedly in a rather alarming way. 
I
>assume its protection methods were not Master compatible for some
reason.
>Does anyone know why?

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.

>Getting old games running on my Master became another reason to have to
>hack into their innards.  The usual things which screwed up on a Master
>were OS1.20 only calls (all Ultimate games, Wizadore, Boffin, Way of the
>Exploding Fist and many others), undocumented 6502 instructions (Zalaga,
>Repton), plotting characters directly from the character set stored at
>&C000-&C2F7 in OS1.20 (all Ultimate games - again), referencing the
screen
>row lookup table in OS1.20 (Castle Quest, Frak) and poking UDG
definitions
>straight into &C00-&CFF (loads of stuff was guilty of this).  It was a
>great way of learning things about the Beeb though.  I never did quite
get
>Frak working ok... I found knives and stuff appearing and disappearing
>randomly.  And as for Alien8.... grrrrrr.....

Not many developers were shying away from lots of low level
assumptions back then ... Possibly nobody deemed the Master
market interesting enough to give up on all those weird and
wonderful protection methods. Which didn't work anyway, but
what did they know ...


John Kortink