J-Cart based multiplayer games do not work.

[SpookySquidGames]

When trying to play J-Cart based four player games with multitap turned on in the core, gamepads stop working and the extra players are not detected. Traditional multitap games work fine.

J-Cart were the special cartridges with two controller ports built into them to handle 4 player games. I've been testing with the European Micromachines games which used these carts. With multitap turned off in the core options they function fine as regular 2 player games. With multitap turned on none of the gamepads work, not even player 1. It also looks like the game is not detecting that it's a J-Cart at all, normally the title screen would display options for 3 and 4 player races but it's only showing 1 and 2 player options.

Traditional multitap games such as Bomberman work fine when multitap is turned on, all 4 controllers are responsive and mapped to the appropriate player.