A jumper is a small metal connector with a plastic cover used to connect two metal pins together. A jumper is normally located in a jumper block. Pins protrude upward from the jumper block. A jumper IS enabled when it is placed over tow pins. When the jumper is removed, the connection between the pins is disabled. jumper blocks are normally labeled JP1, jP2, JP3, etc. on the motherboard. A motherboard manufacturer determines rhe motherboard configuration, the number of jumpers on the motherboard, the jumper labels and use for each jumper. Each jumper can: have more than one setting. For example, consider a motherboard with a jumper block and three pins labeled 1, 2, and 3. The jumper can be placed over pins 1 and 2 for one setting or pins 2 and 3 for a different setting. For example, jumper pins 1 and 2 may need to be jumpered together to configure the motherboard for a 166 MH: microprocessor. In that case, the jumper is placed over pins 1 and 2; pin 3 is left uncovered. When a jumper is not in use, instead of putting it in some isolated place like a desk drawer, place the jumper over a single pin in the jumper block Although connecting to the jumper over a single pm does not enable anything, it keeps the jumper safe and convenient for future use.

Here is a list of the settings that you are most likely to find in a manual:
• Processor/CPU Voltage
• Processor Speed / Bus Speed / Multiplier
• Processor Type
• Cache Size and Type
• Memory SizelType
• Flash BIOS Enable
• CMOS Clear
• Battery Source
• Disable Jumpers

Processor/CPU Voltage: Almost all newer boards have one or more jumpers to set the voltage for the processor. Obviously, this needs to be set correctly or you risk destroying the chip. In addition, newer processors use two voltages: an "external" I/O voltage and an "internal" core voltage. For your motherboard to support these newer processors, it 1, must have jumpers to set both of these voltage types. metimes there can be a mismatch between the e \Olta~e that the processor requires and the voltage rs that the motherboard supplies. This often happens or kcause the motherboard is designed to support a new processor based on the spec, but the voltage is a (hanged for design reasons later on. You should )ntact the motherboard manufacturer in this case. sually you can still use. the processor if the Motherboard can supply a voltage close to the number required-say, within 0.1 V-because processors have Hange of voltages they can use, not just a single number. See here for more on processor voltages.

Processor Speed / Bus Speed / Multiplier: Every therboard has a way to specify the speed of the processor. There are two main methods for selecting [Ioce or speed, and your manual will show you which n reed does your motherboard use. Some mtherboards provide a list of the various speeds ported, and a diagram of how to set the jumpers match that speed. Others require you to set two rate jumpers: one controls the memory bus speed, and the other sets the processor "multiplier". A multiplier is a Dumber that, when multiplied by the bus speed, gives the CPU speed. For example, a 90 MHz Pentium is determined by the 60 MHz bus speed multiplied by 1.5 (the multiplier) yielding 90 MHz. Cnmmon multipliers used are 1.5, 2, 2.5" 3, 3.5, 4, 4.5,5,5.5,6,6.5,7,7.5,8,8.5,9,9.5, and 10. The available multiplier and the bus speed are determined by the motherboard manufacturer. Common motherboard bus speeds include 60, 66, 68, 75, 83, 100, and 133 MHz.

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Processor Type: You may find this instead of, or in addition to, the two settings listed above. In an effort to save the user the hassle of figuring out voltages and speeds, some motherboards combine the jumpers into one jumper set or group. Then, they provide a long list with each processor type and speed that the boq.rd supports, and tell you how to set each of a group of jumpers so that it works appropriately. If you are setting up a PentiL1m 133, you'll find it on the list and be told how to set jumpers 1,3, 7, 12, and 18, for example. The only problem with this arrangement is that unless they also tell you what each of the individual jumpers is actually controlling, it can be difficult to set up a newer processor that may be supported just fine by the board but not be listed in their documentation. You have less information about how the board actually works. You can sometimes find help in this case on the manufacturer's website.

Cache Size and Type: Some boards can have different amounts of cache, and some can have cache either built-in or on a COASt module. There is often a jumper or two to set which is used and how much is on the board. Other boards only come with one arrangement of cache or Can auto-detect when you insert a COASt module, so they will lack these jumpers. Memory Size/Type: Almost all newer PCs auto detect the amount and type of RAM in the system, but many older 486 models require jumpers to be changed when changing the amount of memory .

Flash BIOS Enable: Many boards require you to set a jumper to a special position in order to enable the flash BIOS update feature. This jumper is usually set to the "normal" position except when doing a BIOS update.

CMOS Clear: One of the most famous PC problems is the "lost BIOS setup password" a problem that locks the user out of the BIOS setup program. Some newer PCs have built into the motherboard the ability to clear the BIOS by temporarily setting a jumper and then replacing it (in essence this disconnects the CMOS memory from the battery so it discharges and resets). This jumper is also usually set to the "normal" position.

Disable Jumpers: Some motherboards use special jumpers to enable you to disable parts of the circuitry. This is entirely board-dependent.