Just throw it in the bios folder for any genesis emulator that supports separate lock-on roms (Genesis Plus GX works well), enable it in the options menu, and load up your plain non-Knuckles-including Sonic 2 rom and your Sonic 2 rom will think it's been locked on to Sonic & Knuckles, letting you play Knuckles in Sonic 2 without a standalone KiS2 rom. sk2chip.bin is that separate patch rom, created through fancy commands in the Linux terminal to strip away the Sonic & Knuckles rom and the Sonic 2 rom buried inside a standard KiS2 rom. History: Sonic & Knuckles wasnt a normal cart, it allowed you to stack above it either Sonic 1, 2 or 3 for some extra content. This seperate rom is pretty hard to find online and mostly pointless since you can just get a KiS2 rom easily, but some emulators still support having it as a separate file and locking Sonic 2's rom on without needing a seperate standalone KiS2 rom. This Sonic game is the US English version at. However, Knuckles in Sonic 2 is far more interesting as it actually includes its own seperate rom with patch data that is applied to Sonic 2 containing things like modified level layouts and all the code for Knuckles himself. Sonic And Knuckles & Sonic 2 (JUE) ROM download is available to play for Sega Genesis. For example, Sonic 3 & Knuckles is just Sonic & Knuckles with a few flags in memory set so that it can access Sonic 3's data. Sonic & Knuckles has some weirdness going on with its Lock-On Technology.
