is it not finding the KNOPPIX on the /hxy
as in the wrong number, and you need some sort of
nousb
cheat code
http://www.knoppix.net/wiki/Cheat_Codes
try the
atapicd

or if you get to see where the cd is identified as ..... try
bootfrom=/dev/hdy6

or is it finding the cd and then failing during the boot