[Coco] 64K Mode

[Arthur Flexser]

On Tue, 13 Jan 2004, Brad Grier wrote:

> If I put a coco2 into 64k mode and then build and display a screen 
> somewhere above memory location 0x8000, what would happen if I switched 
> back out to 32k ram as the screen was being displayed? Would I see 
> garbage on the screen or would the image persist?
> 
> The reason I ask is I'm working with a game that puts the intro screens 
> in high memory and then rapidly switches out and back in to 64k mode 
> while waiting for user input. I'm not sure if the game is synchronizing 
> the bank switch with the display somehow or if the screen simply 
> persists from 'high' ram perhaps until a new screen mode or offset is 
> defined.
> 
> 
> 
> Brad
> 

The image would persist.  Above $8000, it is always the contents of RAM,
not ROM (or garbage), that get displayed, regardless of whether ROM or RAM
is switched in there.  This assumes that the machine actually has 64K;  in
a 16K (or 32K piggyback) machine, if I'm recalling correctly, the display 
is just flickery garbage if you try to display nonexistent memory space.

Art