It does irritate me a bit that PPC mobo makers don't take a few leaves from x86 books, particularly with respect to heatsinks.
For example, making it possible for a Socket 7 heatsink/fan to be used on a PPC CPU doesn't necessarily mean having the same socket, it just means having clips in the right places. Then the issue of cooling in PPC machines becomes much easier to address, and solutions far more widely, and cheaply available.
While PPC CPUs don't pump out as much heat, they can't take the heat as well as x86 CPUs can. I wonder if the 970 has had any modifications in this respect.