Anatomy of a Mr. Saturn
In the past I’ve made videos and written plenty of articles about EarthBound’s copy protection. That’s all old news, but recently the question was asked, “How does EarthBound know if it’s on a bootleg cartridge, and why aren’t ROMs affected by this?”
Here was my quick answer, which I later realized might be worth sharing here on EB Central. I tried to explain without talking about SRAM, memory addresses, or other complicated stuff like that, so it’s a bit simplified from what’s actually going on but hopefully it makes sense:
Here’s how the piracy detection works in simple terms.
Each SNES cartridge that has save data in it has a “box” (actually a special chip but let’s just call it a box) for saving data. Different games have different-sized boxes – some games might need to put a lot of stuff in its box, other games might only need to put a few things in its box. Because of this, boxes come in different sizes, and the smaller the box the cheaper it was for companies to use them.
Bootleg cartridges in the 90s would basically just use big boxes ALL the time. It was just easier to do it that way and most games don’t care of the size of the box, all that matters is that the box is big enough.
EarthBound/Mother 2’s piracy detection works by saying, “Okay, we know what the size our box SHOULD be, so let’s try throwing stuff outside of where the box should be. If the stuff still goes into the box, though, that means the box on this cart is actually bigger than it should be, which means it’s almost certainly pirated.”
Hopefully that makes some sense.
Anyway, emulators don’t trip this because there technically ISN’T a box at all. Modern emulators know how to handle box sizes properly automatically. There’s more to it than that but that’s the simple terms.
Of course, not being an emulator author myself I’m sure the emulator part can be explained much better than that, but hopefully that gives the gist of how EarthBound tries to identify a bootleg cartridge.
Also, I’m 99.9% sure MOTHER 2 has this copy protection too, I’ll have to go back and mess around with it one of these days to find out for sure.
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24 Comments to How EarthBound Identifies a Bootleg Cartridge
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