Commonly known as the PIUIO, allows the PC to interface with the JAMMA board (MPUG0PCB002). It slots into a free PCI slot on the motherboard, but electrically is only connected to the PC via USB and a molex connector for power. As such, it doesn't need to be plugged into a PCI slot to function.
Used from the MK6 through MK9, this board is compatible with all PIU games released on the MK6 or later (including current releases).