can not boot from floppy

hello,

I am trying to install netbsd at a rs6000 p43-140, but I can not boot from 
the generic.fs floppy disk.

at boot time I press F8 to enter openfirmware
then I use "boot floppy" command

the server starts to read the disk, but shows not ouput
after reading the disk (I thing the server reads the complete floppy) the 
server stops, no more input is possible.

Any hints ?

Thanky you for your efforts
Uwe