Hi and welcome to HWF. Hope you have a fruitful stay. Jumpers are used to set certain system behaviours by closing (or opening) specialised circuitry. The jumpers themselves are merely pieces of metal designed to close the circuit just like a switch. However, once you position them, the only way to undo the setting is by removing them, in other words jumpers settings are not the sort of setting that you change very often as they require opening your PC case and stuffing your hands in... Jumpers can be used to set a HDD to slave or master (order of access and/or priority) or even speed in which the system retrieves and writes from and to the drive. On the motherboard they can also be used to determine whether your front USB or audio ports work or are disabled. The speed of your CPU and more. One of the most common use of jumpers on a motherboard is to clear and/or protect the motherboard primary bank of settings - the BIOS Each motherboard (or families of boards) may have their own use of jumpers so it is really worth reading the manual in order to understand what system settings can be manipulated by using the jumpers. More here - http://en.wikipedia.org/wiki/Jumper_(computing)
I had them on a 533 fsb P4 asus board. It was only an sd ram one. That was the most recent board. I wonder why they aren't used anymore. lol, Maybe cost?
possibly as auto config or BIOS settings are definitely cheaper to produce, however, i prefered DIP switches to jumpers cos 9 times out of 10 you had a flat blade screwdriver in your hand or mouth or even a philips
