Donkey Kong PK

Donkey Kong XM is an improvement hack of the 7800 port of Donkey Kong that adds improved sound, cutscenes, and the missing pie level. The hack was only released as a physical cart, and it needs an aftermarket passthrough cart, the 7800 Expansion Module (7800 XM), for its enhanced sound.

Donky Kong PK was a later physical release that had additional hardware in the cart so that the 7800 Expansion Module wasn't needed. The only difference between Donkey Kong XM and Donkey Kong PK is the hardware in the cartridge. The game roms are identical.