Pretty straightforward, I go "Config -> Input -> Attach four-score", then "Port 1 -> Configure" and then under "Virtual Gamepad 3" I set some buttons up, either to keyboard or one of my usb gamepads.
Then "Config -> Display -> Input Display -> 4 player" so we can see the presses.
Test the buttons, and they come out all wrong. Press "up" and instead "select" is pressed. Press "start" and instead "B" is pressed. This happens for player 3 and 4, not for player 1 and 2.
I've tested on two seprate computers, using FCEUX 2.2.3, on Windows 10.
It's almost as if the inputs are bitshifted two bits wrong.
So use a more recent version build where this has been fixed
Well FCEUX 2.2.3 is the latest release isnt it?
This is my solution. I'm on a mac so I can't use any other version of FCEUX.
Last edit: Nes Draug 2019-09-17