Thanks for your input!

I go the easy run for the first Version:

I plan to use only 4 player and 4 player Splitscreen games. Therefore i have a 2x2 matrix Controller connected to the Output of the N64. This Controller can show the whole screen on all 4 displays, or 1/4 of the screen on each coresponding display. So you can play N64 multiplayer games in Splitscreen and each player just sees their 1/4 of the screen in fullscreen on his display.

No custom roms, FPGAs etc involved (which is to complicated for me now ;-) )

Crts was also an idea, but as you mentioned it would be very heavy an much bigger...

Flow

Yeah, I never owned an N64 so i didn't cross my mind that this is for 4 player game modes. It's never too late to make something like this though. Shared memory busses for each game instance would be difficult to implement but it can still be done no doubt. It's only within a matter of how much you can fabricate yourself and how possible it is to find the right ICs for the task.

You'll probably need a custom board to make this work properly. You can make a variant of an N64's motherboard using the same components along with 4 ports supporting up to 4 different ROMs. If you actually build this out, it also probably means that you may have to use an FPGA to simulate 4 different instances of the same system running a different game. Perhaps you'd have to make your own toolchain for handling ROM data as well. Maybe you can run a cluster of CRTs instead of LED screens and include speakers at the top of the screen windows for that classic feel. The cabin would also have to be a bit larger in order to do that and would need to support the weight of all four CRTs at the center while also being a bit stylish to better appeal to the players. You could also incorporate some aspect of the classic JAMMA standards too with fully functional coin slots at the bottom but that'd probably mean that you'd have to start writing some custom state control logic. Overall, it's a very cool project and I'd like to make a version 2 of this.