PSU Terminology

The term “rails” refers to the cluster of wires coming from the PSU that ends in a connector. The rail carries a portion of the PSU’s available power to a component. While a single rail can rarely overload a PSU’s power capacity, a unit can inevitably run out of available rails for a particular system. If you’re using a high end graphics card, as well as a NIC, modem, and dual hard drives, then you may notice you need more connectors than your PSU supplies. To rectify this problem, a higher power rated PSU may be necessary.

What is a Watt?

When deciding on a new PSU, you first need to have an idea of your system’s power threshold. How many 4 pin peripheral connectors do you need? Does your computer require more than a 300W unit will provide? If you need a 500W unit, will it provide enough connectors for your current installations? If you have 300W worth of components, then it would not be a good idea to buy a 300W power supply, as it would reach capacity rather quickly. When buying a PSU be sure to purchase a unit with some room to grow. An inadequate power supply can be the key factor to a PC with a seemingly impossible to diagnose general case of intermittent instability.

A watt is a measurement of power, equal to volts multiplied by amperes. The number of volts used to power a component times the amount of current running through the rail. A typical power supply is only about 75% efficient. A GPU that requires 75W of power might actually call in 100W of AC power before losing 25W to dissipation. Newer PSU models have decreased the dissipation significantly. Many newer models receive as well as 93% efficiency ratings.

To determine the power rating necessary for your custom built computer, it would be good to know just how much juice a specific component requires. The people at PCTechBytes.com analyzed typical components of a computer system and how much watts they require while in use.

Modern processors like the AMD Opteron quad core have lowered the watt usage by close to twenty percent. The decrease in power consumption will likely not affect power supplies, but certain elements built into each PSU makes them greener. For years, PSUs have had hibernate and sleep functions built into them. The ability to lessen the computer’s carbon footprint may make for more advances in the way we interact with the PSU, but the biggest difference will come from the computer’s components, having hard drives that require less and less, GPUs that operate at the same level without using quite as much wattage, and other advances in the components’ power use framework.