[Coco] Coco 1 and 2 RAM Expanders (was: Bubble Memory)

[RETRO Innovations]

On 8/15/2017 1:31 PM, Zippster wrote:
> Well that’s true.  If you want the RAM usable by your video pages (VDG), you’ll have to
> interface it directly to the SAM (and data latches) so that interleaved memory access can be used.
>
> You can still bank it with some additional logic outside the SAM of course, but the
> lower address lines have to handled by the SAM.  You’d also need a connection to deal
> with the latches handling RAM data output to the CPU data bus and VDG.
I think my question is more:  If you have access to ~64kB of Video 
memory in "bank" 0, if it were, do you really need access to more RAM 
for the VDG?
>
> I think the easiest way is probably to add additional ram that can’t be accessed for
> video by asserting SLENB to access expansion RAM (this can even be added at the cart port).
I don't think SLENB pages out RAM, just IO.