Tried the PC-Engine core just now, as I see, max. 4 joys are supported, maybe the limit is on firmware level, as other reimplemented hardwares (Amiga, C64, Atari ST) had never option for connect more than 4 controllers at the same time...
My test setup was MiST + 2x USB joypads + 1x USB joystick & 2x DB-9 joys. + 1x USB keyboard (to start the PC-Engine core & load BomberMan ROM).
Enabled multitap option in the menu, could start the game with 5 players, but only 4 could be controlled by the attached peripherials: 2xDB-9 joy (I was able to move, but couln't place a bomb, as the PCE requires 2 fire buttons - a menu option to swap buttons II and I were really appreciated
), and the USB joy and one of the USB gamepads were active (full functionality, bomb placing worked as well), the fifth player at the middle of the screen did not respont to the second USB pad.
Here are some infos about using more than two joysticks:
https://github.com/mist-devel/mist-boar ... eripherals