Computer Power Supply

Selecting a Power Supply

The power supply is what distributes electrical power, at the correct voltages, to the various components and circuits in the computer. Choosing the right power supply is not that hard to do, but trying to get by with one that is under-powered can cause big problems.

Power supply's are rated in terms of watts. The more devices you have in your computer, the more watts the power supply will need to produce to keep everything running at peak efficiency. If you're building just a basic computer, I'd recommend getting something in the 350 to 400 watt range. If you're planning on using multiple hard drives or a mid to high range video card, I'd recommend using a power supply rated at a minimum of 500 watts. If you're planning on using CrossFire or SLI video cards I'd recommend at least a 650 watt power supply.

If the video card(s) (and some other cards) that you choose are the PCI-E type, then they may need their own power source. This is provided by separate connectors from the power supply. If you're using this type card, make sure the power supply that you select has the appropriate connectors.

While we're on connectors, I need to mention the main motherboard power connectors. Power supply's will come with either a 20 pin connector or a 24 pin connector. The same holds true for motherboards; some have 20 pin connectors and some have 24 pin connectors. For the most part, lower end motherboards will usually come with a 20 pin connector while higher end motherboards will come with a 24 pin connector.

If the motherboard you choose has a 20 pin connector and your power supply has a 24 pin connector, don't worry about it. The power supply will still work just fine. The plug on the power supply is made so that it can be plugged into a 20 pin connector with the four extra pins just going nowhere.

If your motherboard has a 24 pin connector and your power supply has a 20 pin connector, you may or may not be ok, depending on the rest of your computer build. If you're using PCI-E type video cards, you really should get a power supply with the 24 pin connector. The four extra pins on the 24 pin connector are for additional power for the PCI-E cards. Preferably, this extra power comes from a separate rail (circuit) on the power supply. There is an adapter made that will convert a 20 pin power supply connector to a 24 pin. In my opinion, this type of adapter is basically useless. It does provide power to the other four pins, but it's splits the power supply rail. This defeats the purpose of having the other pins. It's highly unlikely that you'll do any damage to anything by using the adapter, or not using the adapter. In either case, you'll probably experience some system instability under peak load.

To make things simple, if the motherboard you choose has a 20 pin connector, either type of power supply connector will work. If the motherboard you choose has a 24 pin connector, buy a power supply with a 24 pin connector.