struct MBC5 : MMIO {
  bool ram_enable;    //$0000-1fff
  uint16 rom_select;  //$2000-2fff + $3000-3fff
  uint8 ram_select;   //$4000-5fff

  uint8 mmio_read(uint16 addr);
  void mmio_write(uint16 addr, uint8 data);
  void power();
} mbc5;