First of all. I don't bother under or over clocking a system through the BIOS. This is possible and can yield desired results, however, it is much more unstable.
I use Linux, therefor, I have a nice tool already available to me. It's call cpufreq-selector. It is a command-line tool for choosing CPU frequency settings.
In order to find out if your system supports using this tool is to execute this command.
"cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_available_frequencies"
If you see a list of numbers, your systems supports setting the frequency at any of these speeds.