Here are a few links to consider the speed of cf as well as mmc and sd cards.

http://www.dpreview.com/articles/mediacompare/
http://www.davespda.com/hardware/expansion/cfmmcsd.htm
http://www.amazon.com/exec/obidos/tg...952374-5295339

The general concensus seems to be that cf is the fastest of these three media, but that even it is not as fast as a cd.

Getting Knoppix to run off of this media should be possible as long as your bios supports booting from usb. However as some of the posts at knoppix.net indicate you will have to tweak things because Knoppix is set up by defalut to expect to see itself mounted on a cd.

What's interesting about this approach is not so much the speed of CD's vs the speed of CF cards but rather the fact that you can write to a CF card.

If you do intend to write to it then you will either need to shrink Knoppix, or get a really big CF card (3GB is the largest I've seen) since Knoppix is compressed.