I had the following difficulties starting up 5.1.1:

- black screen -right after the first two lines of code flashed to indicate some activity everything would freeze
- dead mouse - I have a ps/2 optical mouse (the very generic type these days) and it wouldn't move no matter what parameters I've put in the boot code
- the only mode that did produce X window interface was the failsafe but without the mouse working it was challenging to work in (to say the least)

So, after trying out quite a few combination of knoppix cheatcodes here is what solved everything for me (thats HP Core 1.86HZ 2x80HDDs ATI1800):

boot: knoppix acpi=off pnpbios=off noapic noapm xmodule=vesa