Complex sentence: The Atari 7800 allows a game cartridge to contain a POKEY, allowing better sound than the system's audio chip, but only two games make use of this: the ports of "Ballblazer" and "Commando".
Split into simpler sentences: The Atari 7800 allows a game cartridge to contain a POKEY, providing better sound than the system's audio chip. Only two games make use of this: the ports of "Ballblazer" and "Commando".