The short version:
Bought some GBA games on eBay about 15 years ago and just found out TODAY they are actually not original legit Nintendo carts! Found out that most original carts use FLASH or EEPROM to store saves but the bootleg's use SRAM and have patched the ROM's to make it work. The downside of SRAM battery backed savegames is when the battery runs out...it's bye bye savegame! And you can not save with that cart anymore unless you replace that battery.
As usual I started having crazy ideas again and plan on writing a simple NDS homebrew tool to detect these fakes!! Because they are patched versions of the original ROM their hash should not match those known for that game. As a bonus this utility will allow you to backup and restore GBA savegames and possibly make a backup of the ROM too! Just need a name for it better than "nds-gba-checker" as my work-in-progress version is called now, hahaha.
Enjoy the long version if you want, but the above pretty much summarizes what it's about.
The long and hopefully entertaining version:
I think it was around 2005 that I bought my Gameboy Advance SP in the classic NES edition with of course: NES classics Mario bros to go with it. Since most other games were kind of expensive for me back then (don't remember the prices though) I was looking on eBay to what was there. Only buying from local sellers I was assuming people finished those games or just did not like them or something so I bought at least: Supermario Advance, Supermario Advance 2, Zelda: A Link To The Past and Tony hawk's underground after testing them on my flashcard if I liked them or not ...for me that was the reason flash carts were made. Right?
Anyway....buying them on ebay from local sellers I was assuming the games were original and not copies / fakes / counterfeit / bootleg or whatever which they so obviously are! But in my ignorance of my 15 years younger self I had no idea those existed or just did not see the signs. The games played just fine for years so I had no reason to suspect anything was wrong....until a few days ago when I popped in my Zelda and find my 100% completed savegame to be GONE!!! I have never loaned them to anyone who might have erased them as far as I know, so just to see if it might have been the save battery I played a little and created a save. Turned of the system. Back on...and GONE was my save I had just created! Tested it on my SP, NDS, and NDS Lite same results! Taking the cart apart...this is what I found inside:
I have opened it a couple of times now and the first time I did not even notice the bad soldering and the epoxy blob. Just to confirm my suspicion of the empty battery which I saw was enough to just accept it won't be saving anymore, until I get replacement batteries. Then I noticed the exact same on Supermario Advance that it would not hold the save anymore. Since I only had about 6 games anyway I just opened them ALL up to check which of them had the ticking timebomb battery inside of them:
Looking at them like this it's just so obvious to spot the fakes, isn't it ...I feel so stupid. And upset!!! So what is the actual problem with these carts aside from being illegal ofcourse?? They have the game inside that's on the label and at least for a few years saving worked fine. But since original legit Nintendo carts with a very small list of exceptions ALL use either EEPROM or FLASH storage for the savegames, these copies are patched/hacked to save to the SRAM (with battery backup) instead! And from what I have read about these fakes those saving patches are not very stable or reliable. Or if they are the battery they put in might be empty before being send out!! And as you can see on the pictures...the soldering is TERRIBLE on almost all of them! I am surprised they worked at all! Or this long actually. If I had knowingly bought these as "copies" for a cheap price it would have been a different story. I am actually looking into getting some from aliexpress since I have read that you can reprogram some of these with your own GBA homebrew!!! Thinking Batterycheck GBA here ...although it would be a private cart only. No selling allowed and multiple copyright issues in the way of that
Well, at least my newest addition to my GBA collection: Zelda Minish Cap is a legit original Nintendo game cartridge
I was already looking into making backups of my carts and their saves to use on the 3DS with mGBA. Multiple options are possible these days from unbearingly slow (using GBA Gamecube cable) to lighting fast with the Retrode 2 and an adapter. I have a retrode 2 and GB/GBA adapter but I read it does not support the savestate dumping/restore so that sucks. Plus I need to find the retrode in my storage box first . So looking at the GBA cable and the sourcecode of that dumper utility, which I know FIX94 only wrote as a proof-of-concept for those that kept asking if it was possible. And it actually is but it's about a 45min wait to get the data over the stupid cable from the GBA over to the gamecube or wii!! The protocol and electronics in the cable are very inefficient and from what I have seen in the code...FIX94 did a fine job considering the point of his utility. Only with specialized hardware directly on the GBA expansion port...like the wireless adapter. A higher speed "might" be possible according to the docs I found, which defeat the purpose of the "simple and cheap" method of using the cable.
Then I started thinking...and thinking...and thinking.....about the NDS! It has a GBA port with direct access and a way to transfer the data over wifi or store it on the SD card of a slot-1 flashcard. Looking around I noticed there is already a tool for this NDS GBA backup tool...but that was the only one and it does not look like it's open source. Then I found this amusing story about how someone transferred a savegame from a bootleg cart (which he got by accident like me) and transfer it back into an original. Let's sumize his story by saying it's not just copy-paste and he had to go through a few hoops, but he succeeded and sharing his efforts on github. Looking through it he really only made an SRAM savegame dumper for his game, but it shows how to access the cart and read the SRAM holding the savegame. Combining this with the headers of devkitpro NDS I figured out most of the stuff he did...and it's AWESOME. Knowing a tool that worked to dump a cart already existed is one thing...but having an example that mostly does what I need already is even better!
After some more thinking ( I do that to much sometimes ) instead of a pure GBA dumper it might be usefull to have a utility that could detect these fakes by placing them into an NDS and have it verify the GBA ROM in the cart! I have downloaded a list from the no-intro site that lists all known releases and their ROM hashes in CRC32, MD5 and SHA1 to verify the cart with. To do this my utility will read the GBA header to identify the game with it's 4 letter serial code to lookup these hashes and know the size of the ROM to read. Then read in all the bytes from the GBA cart and push the data through the hashing functions and at the end verify them to indicate if it's real or not! I have no idea how reliable this method will be, but if the fakes with SRAM savegames are patched their hash will NOT match the original release. As a side effect of the ROM validation I might as well include a dump feature right? Unless someone has strong arguments to not do this of course. But at least savegame backup/restore is what I want to include in it.
The best advice when buying used GBA carts is, check the average value of the game and if it's way to low...assume it's not an original cart. To help out others I might do another post later to point out what I know about the fakes and how to spot them with detailed pictures of my own. The pictures above I took quickly just to show the insides in this post
Wow, this one got long but hopefully it was interesting to read and have a laugh at me. Either for buying fakes or my crazy ideas and project 10.001
That's all for now.
EDIT: After a quick copy-paste and edit I have a little demo that already looks good in an emulator:
This is from DeSmuME with a Zelda ROM loaded in slot-2
EDIT-2: For those interested in following the NDS app part of this story I have just created a thread for it: https://gbatemp.net/threads/yet-another-way-to-make-gba-backups-with-an-nds.566771/
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