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So.. back in the day, I used to do random PEEKs, POKEs, and CALLs, and there was one particular call that I stumbled upon that could quickly render a disc unbootable. Two questions:

1. Can you give it a try? It's CALL -20480

2. Anyone know what in the hell that one actually does?

It takes about a millisecond to render the disc useless.

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So -20480 works out to be 0xAFFF.

My trusty copy of "What's Where in the Apple", which includes a catalog of where everything is in memory, says that the routine to write the VTOC from its in-memory buffer to disk starts at $AFF8.

The VTOC is the volume table of contents (https://en.wikipedia.org/wiki/Talk%3AApple_DOS#Volume_Table_...), so calling into the middle of that presumably ends up overwriting the VTOC with junk, which would indeed make the disk useless.

Without spending much time on it, you probably jumped to DOS's RWTS or similar and wrote a track out (or something similar). That appears to be 0xAFFF which doesn't ring any bells but is roughly where DOS might load depending on machine/etc.

Try https://github.com/iKarith/beneath-apple-dos/blob/master/ch0... for more info.

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