This is one excellent read! Thanks to the author for writing this down. Not that i'm not interested in the NSA, but this is a welcome diversion. And something I wanted to play with myself for a long time.
I thought it was an excellent experiment and I really appreciate everything you did. I wanted to suggest though, particularly in the "Assembly" part, as an example, that you should link to something like paste bin for the code rather than placing it in-line. Unless you're referring to specific aspects of the code immediately before or after, it's not useful to see the actual code posted in-line, in general. And even then, you should select small snippets of the code (as you did elsewhere in the article). Small nitpick though, thanks for the work, and for writing up everything.
Well you certainly rose to the occasion. I look forward to leisurely reading this in detail.
Before I looked at the article I immediately wondered how you were going to handle self-modifying code (running on the internal RAM of course). I guess you didn't encounter that situation?
Basically I embed an interpreter runtime and use it only when necessary, such as in the case when the program jumps to RAM.
Good point though. I should specifically mention self-modifying code.
Note that with NES games, self modifying code is uncommon, because programs are 32 KB ROM, and you only have 2KB RAM. So you'd have to first copy your subroutine from ROM to RAM, and then jump to it. And then you have that much less RAM to work with.
However, some of the emulator test ROMs[1] people have made use this technique to test every instruction.
