I have the information available in the Cheatcodes:
With DVD version 7.4.0 and upward the bootloader will start the 64bit kernel automatically if a 64bit-capable CPU is detected (if not manually specified otherwise).
Then I have Capricorny's reply on 32 or 64 bit

Which eventually brings me to the obvious question: Is Knoppix 8.6 fully 64 bit? Also, are all packages currently available on the Knoppix DVD 64 bit too?