When DMA is enabled by default many many CDROM drives fail to boot knoppix and the resulting error message does not indicate that it is DMA that is failing. So if it is enabled we have to boot with the cheatcode nodma. We answer For some proof see this http://www.google.com/search?q=nodma+site%3Aknoppix.net or just search the forums for nodma.

I understand your frustration but it looks like the knoppix devels are trying to seek a balance. I would prefer it was to stay enabled but that there would be a huge warning in _FLASHING RED_ that would tell the user: "If this fails to boot, it was probably DMA, so just boot with nodma."