The Mac Pro from 2008 (MacPro3,1) is still a fairly relevant machine in the modern OS X as not only does it run the latest releases of OSX, but also the 8 CPU cores that it came with provide enough power to do all but the most demanding tasks. Yes, they've made faster machines, but this old one still holds its own well enough.
That being said, there was a kernel extension released by ZDNet back in 2008 that allowed you to overclock this specific machine. Though the pages still exist on the web, it seems that after "ZDNet Clock 1.0" was released it was never touched again. Of course, if it worked fine the first time why bother updating it? The only problem is that it is a 32-bit kernel extension and the last version of OS X to support this KExt was 10.7 Lion.
Does anyone know if this tool was ever updated? I'm surprised I really don't see any information on how it is working, but I would hope that someone would have updated it for the modern 64-bit kernel versions? At least if the source was released, someone who has some spare time could pick this one up.
Alternatively, has anyone ever seen a way to overclock a 2008 Mac Pro that works in 10.9 or 10.10? I know I could replace my processors or upgrade, but I think I've got a few years left in this rig.
UPDATED 2015-09-21: still no love on this question, so changed it to at least asking if source code is available.
UPDATED 2017-09-14: two years later, why not try and see if anyone has an answer? Was it ever clear how this worked and why could(n't) it work today on 10.11+?