A word about dumping cartridges

It's one thing to copy cartridges for your own personal use, but if you intend to distribute the ROMs on the Internet, here are a few words of warning (and no, I'm not going to talk about copyright ;-) )

The SMS ROM "scene" has benefitted from being relatively controlled, with dumps being made and released primarily by enthusiasts who take care in documenting the games they dump and ensuring the dumps are good. The MD, NES and SNES scenes by contrast are a total mess, and there are huge numbers of dumps floating around the Internet, with no clue as to their origin or even whether the dumps are good or bad. Projects such as Genesis Power have gone some way towards righting this, but there's still a long way to go.

Bock has expressed concern that some people, having built a SMSReader, may dump ROMs and merrily distribute them online without taking care to ensure a good dump, so we end up with lots more bad dumps and overdumps. Obviously I don't want this to happen, so here are a few guidelines for aspiring ROM dumpers.

Is it already dumped?

If a ROM is already dumped (and known about), it will appear in the MEKA.NAM file supplied with Bock's Meka emulator. If you're unsure if a ROM you have has been dumped before, download the latest version of Meka and load up the ROM in it - if the game name appears in the GUI (as opposed to the message " Game Screen") then it's a known dump. You can also use Maxim's SMS Checker or Cowering's GoodSMS (again, use the latest versions) to try and identify the dump.

Is it a good dump?

You should take precautions to avoid bad dumps (dumps with corrupted or missing data). Use the SMSREAD utility with the verify and (in the case of SMS cartridges) checksum switches, and discard the dump if anything untoward is found. In the case of a European or US SMS game, a bad checksum always indicates a bad dump. (A dump with a good checksum could still be bad, but a dump with a bad checksum is always bad.)

Additionally, you should dump the cartridge several times, removing and re-inserting the cartridge each time (this is important!), and compare the resulting files to ensure they are identical. This helps to eliminate any spurious read errors. A good hex editor, such as Frhed, is recommended for comparing and examining ROM dumps - the Compare from current offset option in Frhed will do a byte-for-byte comparison between the currently loaded file and another, and tell you if the data matches exactly or not.

Also, if you haven't already fitted the two capacitors and resistors mentioned in the solution to problem 1 in the Troubleshooting section, please go and do that now! It will significantly reduce the chances of getting a bad dump.

Is the size correct?

When you dump the ROM, is the resulting file of the correct size? A dump which is bigger than the ROM being dumped is called an overdump; the extra space is filled with mirrored data or blank data, or just garbage. (Mirrored means that the second half of the file is exactly the same as the first.)

When in auto mode, the SMSREAD utility attempts to check for mirrored data, but not for blank data. If you have a 256k file and the last 128k is filled with nothing but FF or 00 bytes, it's safe to say you have an overdump and that the correct ROM size is actually 128k, not 256k. You can use your hex editor to check for this, and to snip the surplus data.

If you know the cartridge size for certain, you should always specify this with the -c switch in SMSREAD. For a US or European SMS cartridge, the size is generally specified by the catalogue number: 4xxx is a 32k game, 5xxx is a 128k game, 7xxx is a 256k game, 9xxx is a 512k game. There are a few rogue titles which break this rule, though.

Any more advice?

Keep and document everything! Each ROM has a story behind it, and a dump released into the ether with no accompanying information is not very useful from an archiving/preservation point of view.

Well-meaning individuals have in the past bought rare and expensive cartridges, dumped them carelessly and then sold them on, so the games only exist as bad dumps with no way of rectifying the situation. Best to do the job properly in the first place.

I have this prototype...

There's nothing like the word "prototype" to send ripples down a collector's spine and have him/her reaching for their wallet :-) A common concern among collectors is that they want to preserve the prototypes they own (EPROMs have a finite shelf-life and will erase themselves eventually), but don't want the dumps released to the public as they fear it will affect the value. This is especially the case in the Atari scene where serious money ($1000s) is paid for prototypes, but in time it could happen more and more with the Sega 8-bit scene too.

Prototypes by their very nature are one-offs, so it's even more important that you dump the games correctly, following all of the advice given above. I hope that in time you'll consider releasing the ROM to the public, but for now just having the game preserved is the important thing.


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