[Coco] Asteroids clone, Star Blaster cartridge?

[Arthur Flexser]

Sounds like somebody patched it so that it could run in a CoCo with less
than 64K, where the usual technique of running it from RAM at $C000 would
not be available.

Art

On Sun, Nov 12, 2017 at 3:48 PM, Darren A <mechacoco at gmail.com> wrote:

> On Sun, Nov 12, 2017 at 1:28 PM, Arthur Flexser wrote:
>
> > In most cases the disk binary is simply the cartridge binary to which a
> > small loader has been attached that copies the code back to the original
> > $C000 location with the machine in the all-RAM mode and jumps to it.
> > (Often, $8000-BFFF is also copied from ROM to RAM in case the cartridge
> > uses calls to Color Basic or Extended Basic.)  The exception would be
> > copy-protected cartridges that are designed not to work from RAM, where
> the
> > loader might contain some pokes to the code to nullify such provisions.
> > Except for such copy-protected cartridges, if should be pretty trivial to
> > strip off the loader and save the rest to generate the cartridge dump.
> >
>
>
> This particular game was not written using position-independent code.  It
> has either been re-assembled or extensively patched such that all absolute
> address operands from C000-DFFF have been changed to 4000-5FFF.
>
> To make a cartridge version, a loader could be added to the image which
> copies the code from ROM down to RAM at $4000 and executes it from there.
>
>
> - Darren
>
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