The Supply Of Power

Everything you need to know about your PSU, and some things you probably didn’t

YOUR RIG DRAWS every watt and volt it uses from one power supply unit (probably). All being well, it will sit quietly in a corner of your case and keep the magic happening. There are only three reasons to buy a new one: your existing one has gone bang or started to smell funny; you are about to embark on serious upgrading; or you’re building a new rig from scratch.

Its job may be vital, but the PSU is often left until last on a component list, using the remaining budget after you’ve picked out the good stuff. A power supply is a power supply—as long as it’s big enough, you just plug it in, and it works, right?

There’s a bit more to it than that. A good one lasts a long time, stays cool, and enables future expansion and stable overclocking. Get it wrong, and you’ll be back ordering another, and possibly other components, too, because when a PSU goes bang, it can take other parts along with it.

The current standard for PSUs is ATX, which surfaced in 1996, replacing the ancient AT. The latest iteration is ATX 2.31, dating from 2008, which shows how leisurely the development of PSU standards is. That’s not to say PSUs aren’t evolving; the huge appetite for power of the graphics sub-system, and the world of overclocking, has put great demands on the PSU. The latest ones are adding digital control circuits; you can even get ones with Bluetooth, so you can run them from a phone app. So, how many watts do you really need? And why do prices vary so much?