Actually, the boot process is a tad more complicated than that. If I remember correctly, mac floppies don't actually use HFS but a similar one. I could be wrong on that, and with me that's always a pretty big possibility. But I remember in the booting docs I came across that there's actually a header in one of the first (if not -the- first) sector of the disk which contains a definition of a sector on the disk containing your bootstrap code for the system to load into memory on boot. I was surprised, I thought it was a higher-level system that essentially just executed finder, but there is a bootstrap in the FS.

I like the idea of programming my own ROM. That sounds fun, I didn't know the SE had a removable ROM but I suppose that makes a lot of sense.

I realize just how much work in the system is carried out by software. The Mac 128k/512k technical details page on wikipedia explained that to me and I found it very interesting.

Oh, and I know about being humbled. I'm a seeming perpetual hardware and software novice with aspirations always a little bit too big for my ability.