I found a solution for myself, thanks to someone on my forum on
mintppc.org. I can now use nouveau normally, to do this there are two
ways, of which the second one is permanent of course:
1. via a kernel command line . In my case, as I use yaboot, I can add
the following kernel command at the second yaboot prompt:
boot: nouveau.noaccel=1
or
2. Edit (nano) /etc/modprobe.d/nouveau.conf to include:
options nouveau noaccel=1