all the extra OS3.5/3.9rom information and any modules you want can be loaded into the kickflash, so instead of your machine having to do 3 reboots from startup, 1 to load 3.9rom stuff, 2 to do the prepemu stuff for fusion, 3 to load anything else you want before the operating system kicks in - your machine just boots up as per normal, because everything is contained in the kickflash which is seen as a "rom" by the machine so gets loaded automatically at startup.
bigger flash chips, like the one on the deneb card can also contain a complete USB stack, so the amiga knows how to use USB devices immediatly, supports booting from USB storage devices, and USB input devices in early startup control etc.
so kickflash type devices are fairly usefull :-)
