Today my new Apple Quad-Core 2.5GHz G5 has arrived. Benjamin Herrenschmid's patches for multi-core Apple G5 boxes work like a charm. The only big issue is the thermal management. I looked into fan control / thermal management a bit, but unfortunately I don't have any time to work on this now, since I'm leaving for a one week tonight :(
You might ask yourself why a Linux kernel hacker buys a Quad Core G5 box at this time, now that Apple has started to sell Intel based boxes. However, this is exactly the reason. At this time, this might be almost the last possibility to get a four-way PPC64 SMP box that is available off-the-shelf.
If I want an x86 box, I wouldn't buy an Apple. The sole reason for having bought and used a number of Apple machines during the last six years was because they're mainstream PPC based hardware.