Date   : Fri, 12 Aug 1994 15:56:39 EST
From   : Stephen Quan <quan@...>
Subject: i see basic! :-)

Thanks for your pointers I finally see BASIC coming up.  I used the
OS ROM hack in James B emulator (Ian Stapleton should get a mention
in here too!) to intercept OSWRCH and OSRDCH and the system booted
up with a prompt.

The source code is in C and has a lot of similarities with James B
compiler, and without his help, Chris Lam and many others on this
discussion list I wouldn't have got this far.  The emulator is
running dismally slow under MS-DOS on a 386DX-33 and 'feels' slow on
a 486DX2-66.  On a 386DX-33 it is operating at about 30 times slower
than a real beeb.

My assembly version of the emulator will be catching soon, I can't
wait to see how big an affect this would make.  I don't have an
anonymous ftp site yet, but I want to make all the work I have done
to this point public domain.

I am now ready to start implement the rest of the BBC, but don't
know where to start.  Any pointers?  My first question is what does
the real OSWRCH and OSRDCH do?  I suspect that I can let the real
OSWRCH loose only when I have implemented some of the 6845, but
without disassembling I am clueless on how OSRDCH might work.
Does it just go into some kind of wait loop waiting for a keyboard
interrupt???

Another question.  The Advance User Guide gives a decent memory
usage for the first couple of pages (my 1 page = 256 bytes).  Things
such as the joystick, the system clock and so on.  When I get around
to emulating those should I directly update these bytes or does some
other ROM do that?  The 6522 perhaps?
-- 
Stephen Quan