[Coco] "VideoPak" hardware question

[Theodore (Alex) Evans]

On 11/09/2014 03:48 PM, Mark McDougall wrote:
> On 10/11/2014 9:23 AM, tonym wrote:
>
>> Would it be possible, similar to how there were 80column cartridges, to
>> make a "VGA Cartridge" for more advanced graphics?
>
> Yes. And it would be quite trivial.
>
> Now all you have to do is decide on the software interface. How/where it
> impacts the Coco memory map, features etc. It would have to be
> completely decoupled from the GIME, as you don't have access to the
> GIME's video timing at all.
>
> Then there's the matter of software support. This is not trivial.

Depending on why one wants this, a logical design might be a serial 
interface through the use of a microcontroller so that it could be 
controlled with a language similar to that used by WINDINT.  With that 
the software for the microcontroller's firmawre would not be that 
complex and the driver for OS-9 should be very simple.  Of course this 
method is not going to let you perform complex changes to the video 
quickly and would end up being similar to the support that drivewire has 
for graphics.  Then there is the question of how many people would 
actually want such a thing given its limitations.