A motherboard power supply, also known as a PSU, provides power to a computer’s components. The ATX form factor is the most common, but newer motherboards use different connectors and require more wattage. Consider the number of connectors, wattage, and quality when choosing a PSU.
A motherboard power supply is the replaceable unit inside a computer that supplies power to the system. Also known as a power supply unit (PSU), it provides the cabling that runs from the unit to the case’s power button, motherboard, drives, graphics card, and fans. The power supply also incorporates a fan to cool the unit, which can run out the back, bottom or top, depending on the model.
As motherboards have evolved over the years, the power supply has evolved as well. In 1995, the Advanced Technology eXtended (ATX) form factor debuted, replacing previous AT motherboards and power supply standards. ATX remains the most common form factor, comprising various versions that represent evolving standards. While many years ago it was simple to buy an ATX power supply for an ATX motherboard, things have gotten a little more complicated.
Aside from the changing connectors used for newer Serial ATA (SATA) drives versus legacy Parallel ATA (PATA) drives, and the ability to run two graphics cards for more bang for your buck, even the way motherboards use the mains has changed. Newer motherboards use a 24-pin main power cable while older motherboards use a 20-pin cable. Some power supplies come with a 20+4 connector that splits to fit both types of motherboard. An adapter may also be purchased to convert one type of connector to another.
In the past, the main power cord was used to power the computer’s processing unit (CPU), but today virtually all current motherboards use a dedicated 12-volt CPU power cord. Again, there are two standards or versions: the 4-pin (P4) and 8-pin (ESP12V) connector. Just like the main power cable, some motherboard power models come with a 12V 4+4 CPU cable to fit both types of motherboard, or you can use an adapter.
If you are working with an older AMD® dual CPU motherboard, you may need a 6-pin auxiliary connector. Most power supplies do not provide this cable, so if your motherboard needs one, you can purchase a compatible power supply.
Older computers derive their power from the 3.3 and 5 volt rails provided by the motherboard power unit, but with the introduction of the AMD® Athlon 64 and Intel® Pentium 4 a new strategy has emerged that uses the 12 volt rail. As a result, power supplies that follow the ATX12V 2.0 (or newer) standard direct most of their power here. If purchasing a PSU for an older motherboard that relies on the 3.3/5 volt rail, consider a motherboard PSU made to the ATX12V 1.3 (or earlier) standard, which supplies most of its driving power from 3.3/5 volts. Alternatively, some newer power supplies provide enough power on both the 12 volt and 3.3/5 volt rails to be compatible with any motherboard.
The number of connectors or cables on the power supply is an important consideration. Some less expensive models have fewer connectors, which may work for some systems, but not for others. Also, modular power supplies are generally a little more expensive, but allow the user to connect only the cables needed, avoiding the clutter of additional cables inside the case. Some enthusiasts, however, shun modular designs, believing plug-in connections are a potential source of unstable power, unlike wired designs.
Another consideration when looking for a motherboard power supply is wattage. There are several calculators available online to get a general idea of which range to consider. The average system with a single graphics card is usually well served by a power supply in the 550 to 650 watt range, but its mileage can vary. Also be sure to check your motherboard specs or manufacturer’s website for power recommendations, as a particular number of amps may be required as a minimum on any given rail.
Not all motherboard power supplies are created equal. Some provide cleaner power, while others might be made with second-rate components. When checking specifications, compare supported or tested hardware, performance ratings, certifications, and warranties as some quality indicators. Customer reviews can also be helpful.
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