Posting this from 8.1 Poor Man's Install. For the first time, I have had to manually set screen resolution - wrong detection left me with an unusable Knoppix.
But, as so often, the knoppix-cheatcodes.txt file helped me out. What I needed, was a specification screen=1920x1200. One might think the norandr alternative would do, but it didn't.
Here are the Knoppix 8.1.0 boot stanzas from legacy grub's menu.lst file. I have added a 1280x1024 frame buffer alternative to have a fallback.
Code:
title Knoppix 8.1.0 64 bits sda1 cloop no persistence fixed screen
kernel (hd0,5)/boot/knx810/linux64 screen=1920x1200 fromhd=/dev/sda1 noimage knoppix_dir=KNOPPIX810_0 nosound keyboard=no ramdisk_size=100000 lang=no apm=power-off initrd=minirt.gz nomce hpsa.hpsa_allow_any=1 loglevel=1 tz=localtime
initrd (hd0,5)/boot/knx810/minirt.gz
title Knoppix 8.1.0 64 bits sda1 cloop fixed screen
kernel (hd0,5)/boot/knx810/linux64 screen=1920x1200 fromhd=/dev/sda1 knoppix_dir=KNOPPIX810_0 nosound keyboard=no ramdisk_size=100000 lang=no apm=power-off initrd=minirt.gz nomce hpsa.hpsa_allow_any=1 loglevel=1 tz=localtime
initrd (hd0,5)/boot/knx810/minirt.gz
title Knoppix 8.1.0 64 bits sda1 cloop fbdev
kernel (hd0,5)/boot/knx810/linux64 fromhd=/dev/sda1 knoppix_dir=KNOPPIX810_0 vga=794 video=1280x1024 xmodule=fbdev nosound keyboard=no ramdisk_size=100000 lang=no apm=power-off initrd=minirt.gz nomce hpsa.hpsa_allow_any=1 loglevel=1 tz=localtime
initrd (hd0,5)/boot/knx810/minirt.gz
By specifying knoppix_dir, and eventually fromhd, I can multi-boot as many Knoppixes I want. I place the kernel and initrd files in separate directories under boot on the partition where grub is installed.
One important reason for having noimage ie. no persistence, boot alternatives, is that I can then backup or copy the persistence file "from within".
Right now, I have 5 live OS alternatives for booting on this old PC: Knoppix 7.05, 7.4.2, 6.7.1 and 8.1.0, and Debian 8.3.0. The old stuff is for running program versions or hardware drivers that can no longer be installed under newer OS versions.