While unloading the raw code from several arcade chips is a simplistic method, loads of titles have continued to be un-dumped and unemulated because of the digital-rights-management system that limits the ROM data from being simply copied off of the core integrated circuitry of the chips. For any of those shielded chips, the decapping method can be employed as a DRM workaround by literally lifting the chip’s “cap” with nitric acid and acetone.
With the underlying winding paths shown within the chip, there exist a few possible ways to know the raw code. For some chips, a piece of sharp soldering to that barred circuitry can allow for a dropped file that gets throughout any DRM extra down the line. In the event of chips that use a non-rewritable Mask ROM, though, the de-cappers can really look within a microscope (or high-resolution scan) to see the hard zeroes and ones that deliver up the contrarily protected ROM code.
Decapping is a time-exhausting and costly process, but the MAME community has shown a compliance to put the work and money. One crowdfunded MAME decapping application from years ago led to the dumping of major chips found in games like Bubble Bobble, Galaga, Arkanoid, Street Fighter EX, and dozens of others. By 2015, though, that work had fallen apart between accusations that a key segment had gone from the Internet and typically run off with dozens of rare chips in his property.
Since then, the Caps0ff plan has taken up the MAME decapping screen, raising money to obtain and de-cap hundreds of un-dumped chips in different states of disrepair. The plan has already submitted detailed breakdowns of its decapping works on chips from games like Bad Dudes, Mortal Kombat 4, and some cult traditional shmups from developer Toaplan, amongst others.
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