I found a free ARM disassembler and took a peek at the firmware for the M3; all I found out for sure is that the first slice of code is at offset 59000h, and that it isn't the code to initialize the DS hardware. I ultimately want to be able to put my own code in place of the stock firmware, but in order to figure that out I'll need to learn some ARM assembly and start tracing around to see where the magic happens. For now I'll have to deal with the clunky firmware, or figure out how to make nonstandard homebrew cooperate with M3Sakura.

I've also been scratching the surface of operating system design, because I'm overambitious. That, and I see a lot of wasted potential in the DS, and Linux takes so much memory and processor time that it's extremely limited. I'm looking to set something up more like RISC OS or AmigaOS, and to take advantage of the ARM7 chip by way of running a Vorbis decoder on it or something. No bloated, useless stuff like memory protection or security.

It probably wouldn't hurt me to do something a little more practical, though, like learning how the sprite system works again :/