#Bad checksum snes9x verification
#Bad checksum snes9x code

This is one of the main reasons we started the original Genesis Power checksum verification effort. If you are really determined, dig out the checksum routine in the cart if it exists and see if it is non-standard. If you get the same result every time, consider the dump to be good even though its checksum is 'misunderstood'. If not, redump the cart a few more times and see if you get the same result (byte-for-byte identical) every time. First, check to see if the standard checksum gives the same result as the header. If you are checking your own cartridges, here is what we suggest. Later models just look for 'SEGA' in the header, and the rest of the header - including the checksum - can be complete garbage (Codemasters games are mostly like this).

The Model 1 Genesis didn't even care if the header was there, so some carts don't have anything where the header should be (Early EA titles like Budokan and Populous, for example). This is commonly seen in EA titles.ģ) The cart doesn't checksum itself, and the company forgot to put the standard checksum in the header.

#Bad checksum snes9x code

This error usually shows up as skipping the first few bytes of the code in the cart, or stopping a page short at the end of the cart, or just an off-by-one error at the beginning or end of the cart.Ģ) The company decided to use a different checksum routine. This gives you a real warm feeling about their ability as game programmers. We have found some standard checksum problems:ġ) The company that wrote the game couldn't code a checksum routine properly. Most games don't bother, so it really doesn't matter what the checksum in the header says. Also, since the Genesis doesn't checksum the cart, it is up to the code in the cart to checksum itself. Therefore, we find quite a few games with 'bad' checksums that are actually correct (we prefer to call them 'misunderstood checksums' rather than doing the non-politically correct thing by labeling them 'bad'). Although Sega recommended the use of a simple 'add up all the bytes in the cart' checksum routine, and most games did this and put the correct value in their header, Sega did not require this. The Genesis does not have a checksum routine built into its BIOS. Not necessarily, although why is a long explanation. Does a bad checksum mean there is something wrong with my cartridge?