If anyone ever thinks of doing another 4000 cpu card then look into the possibility of putting 2M on the card itself and make a connector to the chipram sockets.
The custom chip timing is of course set in stone, but with SRAM you could get a lot more cpu cycles once you stop crossing the custom chips to get to chipram. (Yeah, it would take some extra logic to time and route the cpu signals internally on the card. Don't know if there would be too much noise to connect to the SIMM sockets though...)
