Going back to the op, theres a system routine that loads sectors in at a definate memory location as a trackloader, most of the early multi demo megademo's just intercepted the trackloader and chained each demo in on the system routine. It was a case of capturing the pointer, and handing your own parameters over to the system routine that took over telling it where on the disk etc the data was, and where to put it in memory.
I dont have any examples to hand, but downloading any of the earlier megademo's and disecting the bootblock etc will quickly reveal the technique.
Might just be a bit in the future for you if your still wondering what move.l is about though...
I tried to write a hardware trackloader using the chipset directly once. It went horribly wrong and born of it was a program called the "fast disk destroyer" which could erase a floppy in abour 6 seconds so the most dedicated of disk recovery progs couldnt recover it. I still don't know what I did wrong properly
I learned assembly on the zx81, all those typing in of funny char's after discovering the ansi char for each mnemonic... After that the 64 was easier, but the amiga was just so easy in comparison... all those lovely longwords and stuff... For the first few months I had no compiler, I used to just edit the address space with the instructions and set it as the jump point for the memory monitor. Didnt know better, it was how we'd done stuff on the zx81...