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What is a checksum?

PostPosted: August 22nd, 2008, 3:58 pm
by Blaziken257
I was testing out some games on an emulator called bgb, which isn't what I normally use (I normally use VisualBoyAdvance). Whenever I try playing any hacked games on it (even simple hacks where only the color palette is changed), it warns me about a bad checksum, though it runs the game completely fine anyway. For example, I tried playing the hacked Japanese DKL3 (that I hacked), where I changed the colors around, and it gave me this before the game started up:

Image

Does this mean I hacked the game badly or something? Because when I play it, I don't see anything wrong with it. How does it know that I hacked it? And it does this with other hacks that I play, even ones that I didn't make.

Re: What is a checksum?

PostPosted: August 22nd, 2008, 5:28 pm
by Gnawzooka
What the hell? "A real game boy wouldn't care."? That's an odd computer warning...

Re: What is a checksum?

PostPosted: August 23rd, 2008, 6:31 am
by Kiddy14
A checksum is a way to check if a file or information has errors. When you hack the games, you don't change the info at the beginning of the ROM to make it think the colour palletes you changed (or other things in the hack) are the correct ones; thus giving you a "checksum error". Real gameboys wouldn't care because it's not an original dump, and gameboys don't tell you when there's a checksum error.

http://en.wikipedia.org/wiki/Checksum

Re: What is a checksum?

PostPosted: September 4th, 2008, 7:39 am
by Blaziken257
So if I change just one byte it causes this error? How would I go about making the checksum work properly?