Good find! I didn't know about that site. There was once a text file on how to emulate asteroids, but that fell so far out of date that it's only worth reading for the intuitions about arcade hardware - not so much about how to use the MAME debugger. The link you posted, however, is quite modern and...

There really isn't much written on how to use the internal MAME debugger. It's one of those parts of MAME where, if an individual really needs it, there's a good chance they're some sort of programmer and the MAME source will tell him/her everything they need to know. That being said, there is docum...