Re: [cc65] Target "BBC"

From: Shawn Jefferson <>
Date: 2005-03-30 22:34:40
--- Stephen Thomas <> >
> I've had to put it to one side for now. However, I
> had come to the
> conclusion that supporting the BBC might prove to be
> more awkward than
> it seems at first sight, because the base and end
> addresses of the
> program load area are essentially unknown until
> runtime - the screen
> sits at the top of RAM, taking a mode-dependent
> amount of memory, while
> the OS nabs memory from the lowest addresses - the
> precise amount
> depending on what filing systems are in use.

The Atari 8-bit target behaves in a similiar way.  DOS
usually takes up some low memory, and is dependent on
the DOS.  The Atari linker config decides to start the
program at $2E00 to avoid this area (as well as some
additional room for any loaded drivers.)  It also has
a variable high bound of memory address, that is
pointed to by an OS variable.  The startup code uses
this variable to determine where to put the C stack
and the heap does something similiar (IIRC).

I'm sure you can do something similiar for the BBC. 
The beauty of the cc65 linker is that you can change
addresses pretty easily to suit your own project.

Shawn Jefferson

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Received on Wed Mar 30 22:34:43 2005

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