[Coco] 6 Chip ^809 Computer -> Kipper SBC

[RETRO Innovations]

Looking over the schematic, I'd recommend using a '138/'266 combo to 
decode the address space into 6 chunks and not bother with fully 
decoding the address space for the UART.  It takes a lot of ICs to do 
this, and I feel another option will yield the same benefit.

I recommend the !IOEN line on the expansion port (Kipper Port?) be made 
an input, and that input can be used to map the entire memory map of the 
main board out of the memory map.  That way, additional cards can easily 
move all of the RAM/ROM, and IO out of the way for other stuff (Full 
64kB of RAM, etc.).  The MMU idea floated could be on a secondary card, 
and constrain the mapping of the UART to a specific set of registers in 
the c000-dfff space.  It brings the IC count down to 7 from 9 in the v1 
unit.

Of course, IOEN might be sacred, in which case my idea is not as 
workable.  But, having a pin like that would offer a way to move all or 
part of the onboard memory out of the memory map.

Jim