[notamy]

Yes! Gamesharks / Action Replays / similar gave you an "instruction set" of sorts that was interpreted as instructions of sorts - write value to address, do if value at address is X, and so on. When I was messing with one on the Nintendo DS a few years back, you were actually able to write ARM (and THUMB, I believe) ASM and compile it to the target system (NDS) that could be loaded through the Action Replay. I'll have to check if I can dig up my old notes on this stuff when I'm home...

[voltagex_]

I'd really like to read your notes if you find them. I'm assuming the Action Replay could be used for the first bypass/homebrew loading exploits, then?

[notamy]

I'm not sure; I never got that involved in it. Back when I was involved, there were some communities entirely centered around taking apart individual games and figuring out how to tinker with them. Things like loading up the unused tracks in Mario Kart and changing the colours etc. to make "custom" courses.

Here's one of the main pages I used as a reference at the time: http://doc.kodewerx.org/hacking_nds.html Even without ASM, you could still write to arbitrary memory addresses, jump around with conditionals, patch, copy memory, and all sorts of things. The linked page also touches on the basics of ARM/THUMB ASM tinkering. I seem to have lost my notes, so this is all I can get you :(

[voltagex_]

Thanks anyway. I really like reading about these "unofficial" devices.