- Power supplies are rated or measured in watts. Watts are the measurement of work. In other words, the more wattage, the more work that can be done, and the more components that can be installed. Add the wattage for each component together to find the total wattage needed. Usually, wattage is listed on the device or the documentation for the component. If not, wattage is essentially found by multiplying the voltage and amperage requirements of the component. If a DVD drive requires 1.5 amps (A) at 12 volts (V), then the wattage requirement for the player is 18 watts. Check all the documentation and stickers. Many PC components require two different levels of wattage; use the higher number in calculating minimum wattage.
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A 20+4 pin P1 power connector.After the total power consumption is calculated, and the correct wattage chosen, careful consideration must be made to ensure the P1, or main power connector, matches the motherboard requirements. Motherboards generally require either a 20- or 24-pin P1 connector. A 24-pin power supply will not fit in a 20-pin motherboard, and a 20-pin power supply will not provide enough power for the 24-pin board. If the P1 requirements are not known, a 20+4 power supply can be used. This configuration uses a 20-pin connector plus a four-pin addition if necessary. -
SATA on the left, PATA on the rightThe motherboard is not the only component that could need a specialty connector. Most drives now use the SATA specification for power. This allows the drive to use less power, leading to power savings and smaller power supplies. This connector is black and thin, very different from the Molex connectors that were used for the old PATA specification. - Many new power supplies offer built-in surge suppression. A surge is an unexpected and sudden increase in the amount of power on a line. Since home power is alternating current, there are fluctuations in the amount of power on the line at any given time. This can lead to surges and spikes, which can damage sensitive equipment. While it should not replace a good surge suppressor, a power supply with built-in suppression can help to keep expensive PC parts safe.
- Using a power supply that is too small can lead to a number of issues. The PC may not be able to boot due to lack of power, or it may become obsolete faster because of lack of expandability due to low power. An overworked power supply also causes extra heat, an enemy of PC components. A system will not be damaged by a larger than necessary power supply, but it will add unnecessary expense.
