Uh...read your manual for your motherboard. We can't tell you.
New motherboards typically don't have any jumpers for FSB manipulations. However, in either case, manipulating the jumpers may turn on or off key components on your motherboard related to the control of the FSB. On my motherboard, there are no jumpers, but there is a BIOS setting to turn on the mobo's active overclocking chip. If that chip is on, I can't manually overclock anything. Some boards have a jumper for this instead of a BIOS setting...though it's rare.
You'll just have to read your mobo manual and find out. Best suggestion I can make, besides writing an email to the mobo makers themselves.