[Coco] What would a CoCo successor have to have as a minimum?

Little John sales at gimechip.com
Sat Nov 20 15:23:43 EST 2010

What my son and I have done as far as extending CoCo 3 memory was to map 
register files (or dual port SRAM) at $FF80-$FF8F. These serve to extend the 
MMU to 16-bits. For example, $FFA0 = LSB,$FF80=MSB and so on.This extends 
the coco 3's RAM capacity to 512M or 65536 8K blocks, while remaining 
compatible with existing software. Using the Video Bank Register (the one 
designed by disto to bank the memory as 512K banks for the GIME's video 
circuit) allows 256 512K video banks. So the video can be placed in any 512K 
bank within the first 128Meg. The CPU can access the entire 512M as 8K 
pages. Although the design is complete, it has yet to be prototyped and 

> There is flash memory on the DE1 board and there is 8MBytes of SDRAM which 
> to the best of my knowledge is not used.
> Access to extended memory can easily be achieved by mapping in another 8 
> bit page register in I/O somewhere to extend the memory.
> This would remain backwards compatible with the CoCo3 as the register 
> would not need to be modified for existing programs.

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