[Coco] Cartridge size limit?

[RETRO Innovations]

On 5/3/2016 11:34 PM, Lee Patterson wrote:
> I was thinking in terms of my next Coco 3 based game. Need to get an idea of what I should target. Bouncy Ball is just under 20K. 32K isn't much better, so an MMU system would be preferable if it is cost effective.
As the RoboCop article floating around on the net shows, the design is 
dirt simple:

https://ia700708.us.archive.org/1/items/rainbowmagazine-1990-06/The_Rainbow_Magazine_06_1990.pdf 
(page 60)

'175 CP = !(E & !SCS & !RW) you want the clock line to rise just as the 
cycle ends, so you negate the condition.  Greg used a 74'10 TTL to 
implement this.

So, 2 ICs and you're done.   $.58 for the '175 and .65 for the '00, in 
singles.  Zumwalt's design offers you the option to handle up to 256kB 
of ROM goodness, and adding another '175 for $.58 will slide you up to 4 
Megabytes.  If you only want to target Coco3 with your game, you can 
make your bank size 32kB and then 16 slots would be 512kB, no additional 
logic required.  (but, I'm hoping you don't do this, as it's a dubious 
add and if others emulate the RoboCop/Predator carts, you will not be 
using a compatible option).

a 27C020 would be a great fit for the 256kB game you're going to create, 
and those are $2.00 or so.  $3.20 for parts, $1.00 for the PCB, and 
you're at <$5.00 for the cart HW.

If you're just not into HW, I am sure a handful of folks on here could 
be persuaded to handle it for you for $10.00 a cart, assembled.

What is considered cost effective?

:-)

Jim