Just a note to mention the I-PAC 2 board has undergone re-design. The new board has the following improvements:
Auto-detection of USB/PS2 interface, no jumper to set.
Smaller PCB.
Neater layout, all player 1 inputs along one side, player 2 along the other.
Self-Test LED. This gives an instant indication that everything is OK with the board and wiring. If there is a wiring problem, a flash pattern indicates which input is causing the problem. (The LED feature is lifted from the I-PAC VE board).
On power-up, automatically checks if a valid custom configuration has previously been programmed in, otherwise uses MAME codes.