There is a thread on this somewhere.. You use clockgen, a simple utility that runs up your fsb (along with cpu and everything else). There is no danger, if you go too high, you either freeze and need to reboot or if you go slow like most seasoned overclockers, you will find when your too high way before a freeze happens. What your looking for is dropping out of intensive games, or sound intensive stuff. Onboard sound and memory things usually give long before the cpu does without a way to lock the pci/pcixpress bus. I find that I can run a long time at 4.1ghz, but every once in a while it seems during EQ2 I end up dropping to windows here and there, and sometimes never. So I lower it a bit to 4.02ghz and it never drops. Benchmarks run forever at 4.1ghz, so I suspect the onboard sound is caving it at the increased bus speed. That or some of my 2gig is giving out. EQ2 takes a pile of mem, but benches don't. So no biggie, I'm happily running along at just over 4ghz with no increase in temps.
clockgen for ICS954119 is what the 9860 uses.
Seems most ppl get anywhere from 211-215fsb stable. So don't go over 215 as a general rule. You may get 215, but run a good harsh game to see if it sticks. If it does not, just lower till you get it. One notch at a time. Once settled on something that works for all games and apps, set it to load on bootup and voila' nice cheap boost in speed.