I really enjoy the arcade blogger for the arcade cabinet raid writeups he does, and his step-by-step repair posts. The history aspect is neat too.
This is a repair post with a bit of history.
Decades ago, to combat ROM-cloning piracy, Capcom started adding a chip to their PCBs that stored encryption keys in memory backed up by an onboard battery. You may see the problem here - batteries are not meant to last forever, and if the chip lost power AT ANY TIME the keys were lost and the game was unplayable.
This feels like yet another example of the total disregard corporations hold for the media they own the rights to, in favor of short term profits. We've seen before that many works produced by entire teams would have been lost if not for the efforts of pirates and amateur archivists.
To quote the blog:
Its hard to say if Capcom knew this would happen, but then again, the shelf life of most arcade games was months, or at most a couple of years – I guess it wasn’t something they planned for.
Fortunately, this is a well established problem with a motivated, technically-minded community looking for a solution, so this early DRM has already been circumvented. The article doesn't go into detail on how they researched and reverse engineered this sabotage, but I might do a little reading and edit the post if I find anything cool.
Edit: this seems to have more details and is an interesting read so far: https://arcadehacker.blogspot.com/2014/11/capcom-kabuki-cpu-intro.html?m=1
The gist is that the problem is well solved at this point and there's a small industry of aftermarket components out there that are nearly plug and play. The version the author went with works like this:
You desolder the dead battery and replace it. Then desolder the blank sabotage chip. You swap in the aftermarket one and configure it (by using tiny switches) to inject the correct set of encryption keys. Then you slot the blank sabotage chip into the aftermarket one.
When the game is powered up, the aftermarket chip restores the encryption keys, the PCB looks for the keys, then successfully used them to run the game files.
The cool thing is that the sabotage chip is now functional again on its own.
The author spent some time restoring the board to stock, by keeping the sabotage chip powered with another battery while removing the aftermarket chip so it could be used elsewhere. I should appreciate the effort at not wasting any resources but I think it makes sense to keep the de-sabotauge chip as a permanent addition, as it automatically prevents the kind of data loss the company intended.
Either way, it's a neat article and I'd recommended reading it. He does a lot of arcade cabinet restorations, but generally sends the electronics away for repair, so this was a neat one.
I know tech has come a long way since these were made but there's something to be said for these big, chunky, through-soldered components and the well-documented wiring instructions that often came with them.