it's documented in the Sabayon wiki., but not exactly how-to:http://wiki.sabayonlinux.org/index.php?title=Sabayon_Linux#Boot_parameters_and_workarounds_for_problematic_Hardware
NB! this only works on livecd/dvd's
You can achieve this at boot time, when Grub loads, and present you with a list of options,
e.g. "sabayon forensics, Graphical installation, text installation, etc.
select the entry you want, (mostly the first)
hit F5, followed by ESC.
and on the end of the commandline (Boot Options) that appears,
enter your desired cheat code and hit enter.