Depends on the emulator. For SNES9X TYL 0.0.4me, SMC or zip. For Daedalus, z64. For DGEN, bin, zip and smd are OK. As for GBA, .gba is fine, I'm not sure about zip.

But, for example, if you had a .swc rom for SNES, renaming it to .smc would normally make it work. The same can't be said for .zip.

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