Booting KNOPPIX DVD to ram from grub prompt

I'm trying to boot KNOPPIX to RAM from the grub prompt. Booting using grub> set root=(cd1) grub> linux /boot/isolinux/linux lang=en grub> initrd /boot/isolinux/minirt.gz grub> boot works just fine, but adding the toram parameter causes it to get stuck after pressing Enter on boot. I've seen this question where the poster uses loopback loop /boot/iso/knoppix.iso and bootfrom=.../boot/iso/knoppix.iso. I've tried adding both using /KNOPPIX/bootonly.iso, which is the only .iso file I was able to find on the CD, neither of which helped. I know I should be able to boot the OS to ram from grub as I've done this with other distros. Is there something I'm missing?