Date   : Mon, 04 Mar 1996 20:29:51 +0100
From   : Robert Schmidt <robert@...>
Subject: Re: BBC: Radical rethinks! :-)

>Okay, I thought, what now. I've lost the whole thing (all the code, my 
>copies of the ROMs, the whole lot...) but it's a project I don't want to 
>give up on. So, I thought, I'll write another one.

That's the spirit!

>Introducing... TOL. I think I'll keep the suspense about what it stands 
>for going for a while.

Well, your web page spoils the suspense!  :-)   By the way, your page says
that it is illegal to use copies of the Acorn ROMs.  This is only true if
you don't own a BBC, right?

>tad boring. Thirdly, I don't really know C very well and I think a major 
>project like this would help a lot.

I agree that C is the way to go.  If I was to write an emulator from scratch
(which I am seriously considering), I would even consider using C++, but I
realise that the overheads of C++ will be significant, even though they are
small.  (For example, I like the idea of having a 6502 class, but all that
passing of the "this" pointer around might be enough to kill its usability.)

>So far I have virtually nothing. I have the shell of a program, with 
>...

Check my web pages for info.  There's now a documentation section which
includes specs for the 6502.  As some of you might have noticed already,
I've been requested by Acorn to remove all ROMs with their copyright in
them, so they are not available there anymore (for the time being).  Wouter
Scholten's page has the ROMs on them still, I think...  hmm... checking...
yes, get this link:
http://www.cistron.nl/~wouters/bbc/archive/roms.zip.

>the foggiest idea how I'm going to do graphics or sound support at a 
>later date because I don't know anything about programming either of 
>these under UNIX - if anyone has any ideas on that I'd much appreciate 
>them too.

If I were you I'd grab all the available emulators and steal ideas from
them.  Xbeeb has a reasonably simple screen updating scheme (using X, easily
ported to other graphics systems) and BeebEm uses lots of fancy lookup
tables which I've not been able to figure out completely.

>couple of weeks. Honestly, you've no idea what it feels like to realise 
>that 9000 lines of sweated-over assembler has just gone up in smoke...

Actually I do... ;-)

Good luck on your new project.  We'll be anticipating the day when TOL
spreads its wings and flies!  :)

One thing I'd consider implementing in an emulator is more OS hooks -
especially for graphics functions like line, character and polygon drawing.
If these were executed on the host system instead of through emulated 6502
code in the OS, some programs would really fly (especially BASIC programs).

Does Elite use the standard line drawing functions, or does it provide its
own drawing code?


Regards,
robert



--
Robert Schmidt - robert@...         - http://www.idt.unit.no/~robert
	
	Maintainer of "The BBC lives!" page:  
	http://www.idt.unit.no/~robert/bbc/bbc.html