Date   : Sat, 31 Mar 2007 07:34:23 +0100
From   : info@... (Sprow)
Subject: BBC B progs on a B+128k - any known problems?

In article <460D90B2.7040504@...>,
   Jon Ripley <jon@...> wrote:
> Sprow wrote:
> > In article <20070330131946.9672656B96@...>,
> >    neil f <faz@...> wrote:
> >> If I standardised on a B+64k or B+128k, (as opposed to a plain
> >> B), would I find a lot of B-based programs wouldn't run. 
> > 
> > The most likely cause of pain would be the change from 8271 to 1770 disc
> > controller, in the event that they use any whacky copy protection scheme 
> > on the disc.
>
> IIRC (Ctrl+)Z+Break selects a special compatibility mode that allows 
> greater compatibility with software that expects a BBC B.

You're quite right, it works by mangling the commands sent via OSWord &7F
into the corresponding operation for the 177X. 

If the copy protection involves poking the chip directly it wont help of
course,
Sprow.