So now that we know how a power supply works and how manufacturers try to deceive us, it is time to look at what qualities are desirable when selecting a power supply for your new gaming systems.

Standards: There have always been "standards" in the power supply industry. Early power supplies were on the AT standard. Then came the ATX v1.0-2.0 standards, followed by the current ATX 12V v2.01. The standard versions are usually regulated by Intel and other contributors. Standards are either really important or not that important at all depending on how you look at them. They lay out some basic defaults like fluctuation allowances and amperage on certain rails, as well as interference isolation and minimum efficiency ratings under maximum load. More importantly, they adjust power connector sizes to allow for technologies and support for motherboards. Technically any ATX power supply is backwards and forwards compatible with any other ATX power supply, but it is highly advisable to stick with the latest standard, as it is the best suited for current systems and you will not have to use any adapters.

The most important development in power supplies as far as future technology is concerned is the division of the 12V rail. ATX 12V v2.0 saw that introduction of dual 12V rails, which was a development meant to benefit the new SLi technology from nVidia. Any and every SLi certified power supply that you see will be on the v2.0 or later standard, not that you need an SLi certified power supply to run an SLi system. Power supplies compliant with the ATX 12V v2.0 standard have two 12V taps on the main transformer, which means two 12V rails. The main advantage of the dual 12V rail as I see it is to isolate mechanical interference in the rail. This means that you have one rail dedicated for the most part to mechanical devices such as hard drives, case fans, lights, optical drives, compressors, pumps, and other things that "make noise" when they are operating or starting up. This leaves the other rail for purely electronic devices such as a video card, motherboard, and CPU, which are much more susceptible to damage by fluctuations and interference than are other components.

You don't "need" to have dual 12V rails. In fact, if you are running a system with just one video card, and no huge RAID arrays or a lot case fans and fancy lights, chances are you will see no benefit at all from having dual rails. However, in very noise ridden systems it has proven invaluable. For more on these standards, read up.

The 12V Rail: I mentioned earlier that manufacturers are now relying, almost exclusively, on the 12V rail to provide the high current components of a PC with power. In modern systems, the 12V rail powers all of the most important components. It does not power everything however, 3.3V and 5V rails are not just factors to be disregarded when considering a power supply, they are just of much less importance than the 12V rail. Many of the high-end power supplies featuring just one 12V rail boast tremendous currents, as much as 36A. This is more than enough for any configuration you can throw at it, provided the other rails are also up to scratch. Numbers you should look for on the 12V rail when purchasing a power supply are: >24A on one rail, >16A on each rail in a dual rail setup. These numbers are not necessarily required, but they will likely be adequate for your system now, and allow for at least a little bit of upgradability in the future.

Voltage Stability: There are loads of programs and utilities on the internet that allow you to monitor the voltages of each rail in your power supply. The problem with these utilities is that they are woefully inaccurate. Even the BIOS reports faulty readings most of the time. The only way to truly know the stability of the rails of your power supply is to use a multimeter and test each rail at startup, idle, and load. You should be looking to stay within the tolerance of plus or minus %5 on each rail. You should not test these voltages by yourself without knowing exactly what you are doing. The specifics of this test will be covered in a later article.

In the meantime, you are probably reading this article because you want to buy a power supply, not have one that you want to test. The best way to determine whether or not you will have stable voltages before you buy is by buying from a good manufacturer. It really is as simple as that.

Maximum Power Output: I know I thoroughly trashed this specification earlier, but the fact remains that it is still important. The best way to approach this number is by using a wattage calculator, such as this one. You choose all of your components and at the bottom there will be a nice figure for what the minimum wattage is for your system. This should only be used as a rough guideline for the selection of your power supply. A good thing to do with this number is multiply it by 1.25. This will adjust for any errors that you might have made in configuring the calculator. Then, realize that the produced number is a minimum. Getting an 800W power supply when your system only "needs" 250W is not going to hurt your components. Further, it is not going to make your computer use any more power. It is definately in your best interests to invest in a power supply that is significantly well over the figure produced by that calculator. This will allow you to overclock your current system if you choose to, as well as upgrade it in the future without having to update your power supply.

Value: I will recommend power supplies that are the absolute best. Doing this would mean you are paying a premium for the ultra-high quality. However, once you are at a certain level of quality, it is very difficult to improve upon it, and a lot of different manufacturers fall into this category. This allows for competition across the board, and lowers prices. Looking for the best quality power supply for the lowest price will provide you with the best value, which for most budget-conscience gamers is the way to go.

Noise: Power supplies can be the noisiest component of your system. They are getting better these days with lower speed fans in better configurations and so on and so forth. There are also completely "silent" PSUs out there that are either fanless or fanless up until a certain temperature. This is purely preference, and if sound is not an issue for you then there is no need in even considering how loud your power supply is. Although if it is loud all the time, chances are the components are running at low effeciency producing a lot of heat and keeping the fan at full speed, one sign of a low quality supply.