yoyo@home runs awesome on the G5 series as long as you compile boinc from source and tell it that you are compiling for a ps3. Also since you mention sparc I actually have an ultra 80 loaded with 4 cpu's and 4gb ram but I prefer FBSD on sparc , I have considered it along with my sun blade 100 getting debian installs but I have been to sick to get out to my boinc cluster and work on it.