anyone tried phase change with a power mac? can the g4 or g5 be overclocked that much?

The G5s cannot be overclocked as of yet.  It has not been done.  The G4s dont get hot enough to use phase change systems.  We will have to wait and see how the oc'ing of the mactels goes, but again, they just dont get that hot.

You know, speaking of overclocking... Is there a way to determine a maximum OC for any given processor? Let's say you have a Processor Type A and you get it clocked at 1.0GHz. How are you supposed to determine its maximum possible clock speed (without constant failure/problems)?

This is something I'm very curious about. Perhaps it's best just to let people with money to throw around try it out first and report their findings.

I better get out my money glove if someone has money to throw around.  In all seriousness though, here is how clocking works.  The fab joint makes a fab disk with a ton of cpus on it.  They test each cpus max speed and the "speed bin" them.  What that means is that all Core Duos available are made on the same disks and are the same cpu.  Some of the chips run better than others though, so they are separated into groups of speeds.  Now that I got that out, there is no way to tell how high any given cpu will go.  A Core Duo 2.0ghz may OC to 3.0ghz, but another may only go to 2.2ghz.

Hope that makes sense.

Not only does that make sense, maestro, but it builds off of my previous knowledge (which is that part about how they're all made at the same speed).