Head2Head: Power Supplies

Does absolute power corrupt? We find out with the help of Big Willy...

Your PC is growing.

There was a time when 500 watt power supplies were considered excessive and awesome. They were bought mostly by people with dual socket processors and plans for blitzkrieg-like expansion and were revered by all.

You’d be hard pressed to find anything less than 500W on the shelves now. My how times have changed and other such clichés. Welcome to the relentless pace of technology, gentle reader.

Your computer’s second graphics card, fridge (see here) and old IDE hard drives that you can’t quite bring yourself to image and throw away aren’t going to power themselves. And what about that Crossfire or SLI rig you’ve been considering? Surely that will need all the power in the world.

Or will it?

Thermaltake demonstrated a 2000W power supply at CES a while back, and 1500W PSUs are now being pushed onto us geeks. Should you worried that you’ll need to run extension leads from different parts of your house into your PC just so you don’t trip a circuit while playing Crysis?

What should we make of the silly end of the power supply game? How much do you need? Which ones are any good? Are there any PSUs that are lying to you about their capacity? And at what point exactly can you expect the various high power PSUs to crap out on you?

Glad you asked. We thought so too. And we’re going to find out. We’re going to find out the proper way.

A rationale for testing
We thought about our setup long and hard. Sure, we could have done it like some other magazines and sites out there, and strung together a bank of resistors and switches. But then we'd have a static load that resembled a bunch of cinderblocks embedded in chickenwire. It wouldn't just be a synthetic test, it would be a static one too.

We’re testing computer power supplies here. Computers are not static loads and don't draw power like an array of resistors. They draw varying amounts of power depending on how hard they're working at any given moment.
When a computer starts, so do the DC motors in fans and hard drives. Starting a DC motor takes more power than keeping it running. The capacitors and inductors that litter motherboards have to be charged on startup, which creates an inrush of current. In practice, it means the 12 volt line sags on crappier PSUs. Best believe we’ll be pointing this out if and when it happens.

And that’s just during startup. When you’re playing a game and your GPU silicon needs to render unpredictable frames, it asks for epic amounts of current. More than your motherboard can supply in fact – which is why so many additional 12 volt lines get hooked into it directly from the power supply.
Nope. A static load wasn't going to cut it.

So we built something that would.