Date   : Fri, 26 Jun 1998 11:48:39 +0200
From   : Hubert Nooijen <Hubert.Nooijen@...>
Subject: Re: BBC Master

Actually, the situation is less complicated than one might think so.
Back in 1986, when I upgraded from a BBC B to a Master 128, I discovered
that a certain amount of the incompatible games directly addressed
specific routines in the BBC B's OS 1.2 ROM. These routines were less
than 512 bytes in size and relocatable.
Now the trick: since the memory map of the Master shows a spare 512
bytes RAM block in the ROM area, I decided to extract the needed block
of code from the original OS ROM and put this in the spare RAM area.
Then, with a suitable disassembler/memory editor like ADT the jump
addresses of the games in question were adjusted to point to the new
location. And guess what? Nearly all those games which have been
modified this way (about 25 in total) ran without a hitch on the Master,
including the venerable Castle Quest, of which it was said that it was
"definitely not Master compatible"!

Regards,
Hubert Nooijen

--
H.W. Nooijen
Software Engineer
Vision Software & Services BV
P.O. Box 356
3430 AJ  NIEUWEGEIN
The Netherlands
phone: (+31) (0)30-6001400, 
fax: (+31) (0)30-6001401
hubert.nooijen@...      
http://www.vision.nl
--



> -----Original Message-----
> From:     Stuart William McConnachie [SMTP:stuart@...              ]
> Sent:     donderdag 25 juni 1998 19:52
> To:       Francis Muir
> Cc:       bbc-micro@...          
> Subject:  Re: [BBC-Micro] BBC Master
> 
> In message <19980625074808.23536.qmail@...        >, Francis Muir
> <francis_muir@...        > writes
> >I've just acquired a BBC Master over ten years after I last used a
> BBC 
> >micro.  However, I still  had all my old software and was excited
> about 
> >being able to use all my old programs.
> >
> >Unfortunately, most of them don't work on a Master (I used to use a
> BBC 
> >B 32k).  My two favourite games Repton and Zalaga don't work, nor do 
> >numerous other educational programs.
> Zalaga will never work.  Orlando used some illegal (unsupported)
> machine
> code instructions which were only available on the 6502 processor that
> was in the BBC B.  The Master had the more advanced 65C12.  Some of
> the
> other software *may* work, if you configure the machine correctly.
> For
> example disable the shadow RAM.
> 
> Of course you could try emulating the Beeb on your PC! :-)  Try pcBBC
> http://www.bburne.demon.co.uk/bbc.html
> It certainly runs the two games you mention!
> 
> Regards,
> -- 
> Stuart McConnachie (stuart@...              )
> 43 The Hollows, Long Eaton, Nottingham, NG10 2ES, UK
> Mobile: 0966 224307