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Tips for Buying EarthBound

March 8th, 2013 | EarthBound, Uncommon Knowledge

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

The Man With No Name said on Mar. 8, 2013

So because the pirated carts have more space to save the game, it knows its pirated? Is that the general jist of it?

Mato said on Mar. 8, 2013

Yep, basically. I shoulda just said that, it’s much easier to understand, heh.

Geppu said on Mar. 8, 2013

Never thought my question would be posted on EarthBound Central! 🙂 Thanks again for your informative answer.

Daniel said on Mar. 8, 2013

Interesting. I wondered about that too.

thelucaskid482 said on Mar. 8, 2013

Just another way EarthBound is better than anything else. Ever.

Halloween said on Mar. 8, 2013

I always find it interesting how people worked with computers in the 8 and 16 bit days. With the limited technology it’s sometimes less intuitive but obviously easier to understand. They couldn’t just connect to the Internet and check a sum, they had to think about everything that a pirated game is and what (out of the limited) operations they could perform. I remember every time I looked at an 8085 or a ROM in school the single thing on my mind was “NINTENDO”.

Midna said on Mar. 8, 2013

Mother 2 does have the copy-protection, according to The Cutting Room Floor.

Opinionated Vector Chimera said on Mar. 8, 2013

I find Mato’s given explanation very confusing, but I already know that EarthBound punishes save files with a size over 8 KB.

Also, one time, I used PK Hack to put Kraken into regular formations, and an incompatibility error (read: “This is a PAL SNES, dumbass.”) came up when I loaded up a save state in Deep Darkness. I’d like to know how that works, but the ROM I was working with was already screwed to the side from excessive use of PK Hack. The error didn’t pop up once I reverted the ROM and made other slight changes.

Co-Wink-Key-Dink inc said on Mar. 8, 2013

It really said “dumbass”?!

goveynetcom said on Mar. 8, 2013

Also why EarthBound doesn’t work well with copiers. They have the same principle, uses a massive save file (the one I have uses 128 kb instead of proper sized saves), still testing to see if it can be beaten since I fixed the save file manually (when it saves the sram it dumps a bunch of stuff outside the bounds of a normal sram file, filling it with null data might do the trick). But EarthBound is quite the picky game, 😛 works well to keep imposters away.

Anonymous said on Mar. 9, 2013

The emulator knows what size box the game expects because it’s given that information, either added in when the game is copied to a ROM or as part of information about the game stored within the ROM. So the emulator creates a virtual box of the correct dimensions, which works just like the one in the cartridge and thus passes the piracy test.

KingOfSwords said on Mar. 9, 2013

So, if EarthBound was put on a bootleg cartridge with the correct-size box, it would work fine?

Vukadin said on Mar. 9, 2013


Pretty much.

AdmiralCrunch said on Mar. 9, 2013

Minor point @KingOfSwords & @Vukadin, the copy protection would not freak out, but other issues such as the illegality of it and the generally low reliabilty of bootlegs would still plague it! Mato has written several articles about bootleg EB carts and the issues with them. Interesting read.

Opinionated Vector Chimera said on Mar. 9, 2013

@Co-Wink-Key-Dink inc

That was paraphrasing. Nintendo would not let a word like that pass through.

If you do want some screenshots of the actual screens, they’re here: http://tcrf.net/EarthBound#Copy_Protection.

J said on Mar. 9, 2013

I actually have an Earthbound Repo, I have no idea what the game originally was. But the cartridge doesn’t look the same as my real copy and the sticker(Label) well, its not even close to the original, its home made.

The game plays fine and saves right to the end, including finishing the final boss.

Guess whoever did this one knew what he was doing.

Anonymous said on Mar. 11, 2013

So does that mean if you try to play EarthBound on a SNES flash cart, the anti-piracy measures will come up? Or do newer flash carts have a way to get around that, too?

Mato said on Mar. 11, 2013

I don’t know much about flash carts so I can’t say. I imagine modern flash carts would be more sophisticated and capable of handling this stuff, but I dunno since I don’t have one.

Anonymous said on Mar. 11, 2013

Has anyone checked to see if this is in the GBA port as well?

Apple Kid said on Mar. 11, 2013

I think gba bootlegs would be less common and they might have been pressed for room (after all, it’s a 2-in-1 deal). I think it would no longer be there but would knows.

Angryrider said on Mar. 13, 2013

But what about on an Everdrive? How does the rom know about the size of the box?

Mato said on Mar. 13, 2013

Yeah, see my comment above – I don’t have any experience using flash carts so I don’t know how they work. I imagine modern flash carts/bootlegs are more sophisticated. It’s been almost 20 years since Mother 2 came out, after all. That’s like ancient history in terms of technology improvements.

I’d definitely like to get my hands on a flash cart or two someday, maybe just to do homebrew stuff but also to figure out stuff like this.

StriderVM said on Jun. 4, 2013

“So does that mean if you try to play EarthBound on a SNES flash cart, the anti-piracy measures will come up? Or do newer flash carts have a way just to get around that, too?”

It depends on how the cart was “reproduced”. For example, ROM dumpers at the time (That dumps to floppy disks) do it differently, old/outdated ones just use the biggest box possible in that hardware (Typically 2MBit, 256Kbit data) . So it triggers the anti piracy code. While more recent ones have settings that allow you to set how big the SRAM is, which when the proper settings are used, will not trigger the anti piracy.

StriderVM said on Jun. 4, 2013

All in all it depends on the flash card or ROM dumper. Some are dumb and some are not. I’ve actually seen bootleg copies that trip the anti piracy code and the pirates either don’t realize that or think it’s a feature of the game.


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