In most cases, you adjust the FSB in small increments. FSB + Multiplier = Clock Speed. So a FSB of 200 Mhz and a Multiplier of 11 will yield a 2.2 Ghz CPU speed. If you were to up the FSB to 220 Mhz and keep the 11 Multiplier, your CPU would run at 2.42 Ghz. If you upped the FSB to 220 and dropped (if you're able to) the multiplier to 10, it would remain 2.2 Ghz.
Some BIOSes...BIOSi...BIOS'seseses
will let you adjust the multiplier within a certain Min/Max range - sort of like what EIST does, but it stays that way until you change the settings back.