Thanks for the replies. Debian wheezy powerpc installed without any problems at all. I can't really control the writer's speed. I used a CDRW which listed only one speed (10x) but everything worked out alright in the end.
Unfortunately, I got a bit greedy and selected the LXDE desktop which boots properly all the way to the graphic environment and then into a black screen.
I tried to cycle through different graphic modes but I may be doing something wrong here, is it still Ctrl-Command- (plus or minus) to cycle through valid modes?
If i double click "enter" I can see the monitor flicking.
Worst case scenario would be to re-install, which I would like to avoid if possible.