Après quelques recherches sur le net, j'ai trouvé quelques infos :
En version 4P il faut 4 monnayeurs.
Si tu peux choisir tes personnages, c'est que tu as une version 2P, sinon c'est une 4P.
Le driver de mame, a 2 coins entry en 2P et 4 coin entry en 4P.
static INPUT_PORTS_START( simpsons )
PORT_START("P1")
KONAMI8_B12_START(1)
PORT_START("P2")
KONAMI8_B12_START(2)
PORT_START("P3")
KONAMI8_B12_START(3)
PORT_START("P4")
KONAMI8_B12_START(4)
PORT_START("COIN")
PORT_BIT( 0x01, IP_ACTIVE_LOW, IPT_COIN1 )
PORT_BIT( 0x02, IP_ACTIVE_LOW, IPT_COIN2 )
PORT_BIT( 0x04, IP_ACTIVE_LOW, IPT_COIN3 )
PORT_BIT( 0x08, IP_ACTIVE_LOW, IPT_COIN4 )
PORT_BIT( 0x10, IP_ACTIVE_LOW, IPT_UNKNOWN ) //SERVICE1 Unused
PORT_BIT( 0x20, IP_ACTIVE_LOW, IPT_UNKNOWN ) //SERVICE2 Unused
PORT_BIT( 0x40, IP_ACTIVE_LOW, IPT_UNKNOWN ) //SERVICE3 Unused
PORT_BIT( 0x80, IP_ACTIVE_LOW, IPT_UNKNOWN ) //SERVICE4 Unused
PORT_START("TEST")
PORT_SERVICE_NO_TOGGLE( 0x01, IP_ACTIVE_LOW )
...
INPUT_PORTS_END
static INPUT_PORTS_START( simpsn2p )
PORT_START("P1")
KONAMI8_B12_START(1)
PORT_START("P2")
KONAMI8_B12_START(2)
PORT_START("P3")
PORT_BIT( 0xff, IP_ACTIVE_LOW, IPT_UNUSED )
PORT_START("P4")
PORT_BIT( 0xff, IP_ACTIVE_LOW, IPT_UNUSED )
PORT_START("COIN") /* IN4 */
PORT_BIT( 0x01, IP_ACTIVE_LOW, IPT_COIN1 )
PORT_BIT( 0x02, IP_ACTIVE_LOW, IPT_COIN2 )
PORT_BIT( 0x04, IP_ACTIVE_LOW, IPT_UNKNOWN ) //COIN3 Unused
PORT_BIT( 0x08, IP_ACTIVE_LOW, IPT_UNKNOWN ) //COIN4 Unused
PORT_BIT( 0x10, IP_ACTIVE_LOW, IPT_SERVICE1 )
PORT_BIT( 0x20, IP_ACTIVE_LOW, IPT_UNKNOWN ) //SERVICE2 Unused
PORT_BIT( 0x40, IP_ACTIVE_LOW, IPT_UNKNOWN ) //SERVICE3 Unused
PORT_BIT( 0x80, IP_ACTIVE_LOW, IPT_UNKNOWN ) //SERVICE4 Unused
PORT_START("TEST")
PORT_SERVICE_NO_TOGGLE( 0x01, IP_ACTIVE_LOW )
......
INPUT_PORTS_END
Donc, puisque ta dédié n'a qu'un seul monnayeur, il faut que tu ailles dans le menu de réglage, et cherche si il n'y a pas une option pour créditer n'importe quel player.
Sinon tu peux essayer le menu de config et chercher le set qui te conviens avec mame.
GAME( 1991, simpsons2p, simpsons, simpsons, simpsn2p, driver_device, 0, ROT0, "Konami", "The Simpsons (2 Players World, set 1)", GAME_SUPPORTS_SAVE )
GAME( 1991, simpsons2p2, simpsons, simpsons, simpsons, driver_device, 0, ROT0, "Konami", "The Simpsons (2 Players World, set 2)", GAME_SUPPORTS_SAVE )
GAME( 1991, simpsons2p3, simpsons, simpsons, simpsn2p, driver_device, 0, ROT0, "Konami", "The Simpsons (2 Players World, set 3)", GAME_SUPPORTS_SAVE )
GAME( 1991, simpsons2pa, simpsons, simpsons, simpsn2p, driver_device, 0, ROT0, "Konami", "The Simpsons (2 Players Asia)", GAME_SUPPORTS_SAVE )
GAME( 1991, simpsons2pj, simpsons, simpsons, simpsn2p, driver_device, 0, ROT0, "Konami", "The Simpsons (2 Players Japan)", GAME_SUPPORTS_SAVE )