[Coco] How does the cartridge port work, anyway?

John W. Linville linville at tuxdriver.com
Thu Feb 21 18:19:37 EST 2013

On Thu, Feb 21, 2013 at 05:06:26PM -0600, Allen Huffman wrote:
> On Feb 15, 2013, at 4:05 AM, Phill Harvey-Smith <afra at ramoth.org.uk> wrote:
> > The other way that this can happen of course is if the cartridge has it's own address decoding and holds the "device select disable" line low it can pretty much override the internal memory decoding.
> > 
> > This could for example be used to map an external ROM / RAM into the
> > area that the basic roms normally occupy.
> How big of an area could a cartridge map in this way? Did anything do that?

Such a cartridge could cover all 64K, or beyond if it had its own
bank swapping hardware.

Someone had a cool project on coco3.com that used this technique to
basically replace the 6809 with an external processor -- too bad that
his site seems to have disappeared...


John W. Linville		Someday the world will need a hero, and you
linville at tuxdriver.com			might be all we have.  Be ready.

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