Voltage can be raised to increase stability in the cpu in order to obtain a higher clock speed that you wouldnt normally get using the cpu's standard voltage. Celerons run at 2.0v, k62's at 2.2v and 2.4v so you will have to raise it to a higher voltage to get a stable system. If you have to raise your voltage to high though and your chip still isnt stable then dont push it, your cpu probably cant cope too well with overclocking. In the same light dont push a cyrix chip in this manner unless you have very good cooling, you have been warned. Remember to set it .1v at a time till it runs stable, dont try and set it insanely high the first time or you could fry it. Please remember that when you raise the voltage on your shiny new p3 beast that it will create a lot more heat, so get some thermal paste onto it quick and a couple of extra fans wouldnt hurt either. The main thing to remember with voltage is DONT PUSH TOO FAR, and KEEP IT COOL.

Pushing your cpu past a full 1v is probably to extreme unless you are running a water cooled cpu or have a peltier attached to it. Although a k6-2 i once owned was a 2.2v cpu i could happily run this at 3.1v all day, but on other similar cpu's it would kill it instantly. Also the cooler the cpu is kept the lower the voltage needs to be.