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How to Choose a Computer Power Supply

What does “ATX” stand for? ATX stands for Advanced Technology eXtended. In summary it defines a set of standards in measurements and forms that helps make things such as computer power supplies interchangeable with one another.

ATXPowerSupplies writes this article on choosing the right power supply for your computer to help you in your decision making process. Whether you are purchasing a power supply for your new computer or just replacing an old one we hope this will help in the selection process.

The first question to ask yourself is, “Is my power supply an ATX form factor?”. If you have this information available then the selection process is much easier. The information is sometimes stamped somewhere on the power supply or may be contained in the manual for your existing computer. If you’re looking for an ATX power supply make sure the power supply is an ATX form factor, not micro ATX or any other.

Perhaps the most method to use in selecting a power supply is comparing the physical dimensions. Make sure your computer case can accommodate the the Height, Width, and Depth of the power supply. If you are replacing an existing power supply then take measurements of it before you discard it. Take a look at the graphic above to gain a better understanding of Height, Width, and Depth. If your power supply is considerable smaller than the typical dimensions of our atx power supplies then it could be possible that you have a micro atx power supplies. If you feel you might have a micro atx power supply then you could compare its dimensions with our 200W micro atx power supply.

After you have chosen your power supply based on physical dimensions you need to take a look at what connectors you need on your power supply. Different power supplies have different connectors so it’s best to choose one with connectors that meet your every need. It’s okay if you buy a power supply and not use some of the connectors. You can just leave them hanging unconnected. Below is pictures of some common connectors found on atx power supplies:
atx connector

20 pin ATX Connector – The 20 pin ATX connector that inserts into an atx motherboard. If your motherboard has a slot for the 20 pin connector shown in the graphic they you can be almost 100% certain that an ATX power supply is required for your motherboard.

Be sure to pay close attention to the number of pins. On some computers we’ve found that this connector contains 24 pins instead of 20.

24 pin ATX Connector – Some computer motherboards require a 24 pin ATX Connector. Given our past experience we advise purchasing a power supply with a 24 pin connector built in rather than a converter that converts the 20 pin to a 24 pin. The converters tend to have poor power distribution while a power supply with the 24 pin connector built in will be powered directly from the power supplies.

P4 Connector – Most motherboards that have Intel Pentium 4 processors will have a slot on the board for this P4 connector. If your motherboard has this slot then make sure you get a power supply with a P4 connector on it. If your motherboard doesn’t have a slot for this connector it is still okay to purchase a power supply with this connector, and leave the P4 connector unconnected.

4 pin IDE Connector – This is the IDE connector that supplies power to your hard drives and cdroms. Most atx power supplies have 4 connectors of this type included. If you need more than 4 connectors it’s best to purchase y-splitters to increase the number of connectors. Purchasing power supplies with more than 4 connectors can often be much more costly than purchasing a y-splitter.

4 pin floppy connector Floppy Connector – The 4 pin floppy connector supplies power to any floppy drives that may be on your computer. Some of the card reader drives use this connection also. Most atx power supplies have two of these connectors included.

6 AUX connector – Look on your motherboard and see if there is a slot that accepts the 6 pin AUX connector. If there is a slot for it then chances are you’re going to need it.

Sata connector – Hard drives and other devices with sata connectors as shown here are becoming more and more popular. We aren’t sure exactly what the advantages are to this technology, but if you have any devices in your computer that use the sata connector you’re going to need a power supply with sata connectors.

You need to know how much power you’re going to need. It’s okay to buy a power supply that is larger than necessary because the power supply will step down to your power requirements. On the other hand, buying a power supply that is too small for your requirements will be annoying. Many times people will complain of their computer rebooting for no reason at all. Nine times out of ten the reason for this is an undersized power supply. Many companies that sell computers will install an undersized power supply to save money and increase profit margins. Buyer beware!