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Eleven enthusiast power supplies compared

A bevy of PSUs encounter The Beast

Today's PCs are filled with mind-bendingly complex bits of engineering. Processors with multiple cores pack millions of transistors onto excruciatingly sterile shreds of silicon smaller than the average postage stamp. As if that weren't impressive enough, those millions of transistors can flip bits billions of times per second—seemingly an entire world's worth of activity in just the blink of an eye. Chips get even more complex when we dive into the world of graphics, where transistor counts multiply and the number of effective cores working in tandem grows exponentially. Here, the cutting edge really does look and feel the part, and the results can be spectacular.

Not so much for power supplies. At least in terms of the components inside a modern PC, the power supply is relatively simple fare—mere electrical engineering in a world that bears an increasing resemblance to computer science fiction. Yet power supplies are so often done poorly. PSUs with sagging voltages or otherwise dirty power are commonly the root of system stability issues. What's more, they can effectively spread disease, taking other components with them as they spiral into an untimely demise.

Getting a power supply right shouldn't be hard; a good PSU needs only to be quiet, efficient, reliable, and deliver enough pristine voltage to satisfy a given wattage requirement. So which power supplies are the quietest and the most efficient? More importantly, whose power is the cleanest? To find out, we've pushed 11 enthusiast-oriented PSUs to their limits through a brutal gauntlet of tests. Read on for the results.

Lining up the competition
Power supplies are relatively straightforward products, making them easy to compare. Here are some of the vitals of the 11 units we'll be looking at today.

Wattage Cooling Modular? 80 Plus? Warranty Price
Antec EarthWatts 500W 500W 80mm rear No Yes 3 years
Antec Neo HE 550W 550W 80mm rear Yes No 5 years
Antec TruePower Trio 650W 650W 120mm bottom No No 5 years
Cooler Master Real Power Pro 550W 550W 120mm bottom No Yes 5 years
Cooler Master Real Power Pro 650W 650W 120mm bottom No Yes 5 years
Corsair HX 620W 620W 120mm bottom Yes No 5 years
Enermax Infiniti 720W 720W 140mm bottom Yes Yes 3 years
OCZ GameXStream 700W 700W 120mm bottom No No 3 years
PC Power & Cooling Silencer 750W 750W 80mm rear No Yes 5 years
Seasonic S12II 500W 500W 120mm bottom No Yes 3 years $109.99
ThermalTake Toughpower 700W 700W 140mm bottom Yes No 5 years

As you can see, we've limited this batch to models with output ratings between 500 and 750 watts. Sure you can now get PSUs rated for a kilowatt or more, but that much power is only necessary for the most extreme high-end systems. Or perhaps a wildly overclocked Prescott. Most enthusiast systems should be more than comfortable with between 500 and 750W at their disposal.

Incidentally, we tried to get a generic 500W model to throw into the mix, but were thwarted by a general lack of availability. It seems generics don't typically aspire to output capacities of 500W or greater, and those that do don't cost much less than brand names with similar wattage ratings. This is a good thing for consumers, of course.

Among the units we'll be looking at today, PC Power & Cooling's Silencer packs the most grunt at 750W. 500W models from Antec and Seasonic round out the low end of the wattage spectrum, with everyone else falling into place between those extremes. A higher wattage rating doesn't necessarily guarantee quality, though. We've designed our test suite to ensure lower-wattage models aren't penalized for bringing fewer watts to the table.

Wattage ratings determine how much power a system can squeeze from a PSU, but a power supply's actual socket draw is often much higher. This discrepancy is caused by inefficiencies in the power supply's conversion of AC to DC power. Some do a better job than others, and the industry has come up with an "80 Plus" moniker to denote PSUs that are at least 80% efficient. Only about half of the power supplies in this group have an 80 Plus rating. Interestingly, some of the PSUs that lack the 80 Plus logo still come with claimed efficiency ratings of over 80%. We'll be testing efficiency ourselves, so we can see whether the 80 Plus-certified units really are more efficient.

Reliability is more difficult to quantify than efficiency, but certainly no less important. Unfortunately, it's impossible to test long-term reliability for a round-up like this. We can make some assumptions based on the warranty coverage offered by each manufacturer, though. Three years seems to be the standard for enthusiast-oriented PSUs, and you get at least that much coverage with each of the units we're looking at today. However, Corsair, PC Power & Cooling, and ThermalTake extend their warranty coverage to five years, giving them an edge on that front. Antec also offers fives years of coverage on its Neo HE and TruePower Trio models, but not with the EarthWatts. A longer warranty term doesn't necessarily guarantee a more reliable power supply, of course, but you'll at least be guaranteed a replacement for longer should things go south.

Cooling is important for power supplies on two fronts. Not only do PSUs have to cool their own internal components, but they can also suck a lot of hot air out of the rest of the system. These days, most employ 120mm fans mounted at the bottom of the unit to help draw warm air up from inside the case. ThermalTake and Enermax go even further by tapping massive 140mm fans that should be able to move more air at lower—and, more importantly, quieter—fan speeds. At the other end of the spectrum, we have models from Antec and PC Power & Cooling that rely on a single 80mm exhaust fan at the back of the unit. This old-school approach has been around for ages, and we'll be interested to see how those units' cooling performance and noise levels compare with the others.

Getting a grip on cabling
Modular power supplies have more recently become popular, and four of the models in our group allow the removal of unused power leads to prevent cable clutter. In fact, each of the units we've gathered offers a unique mix of cabling options.

Main power Aux 12V PCIe 4-pin peripheral SATA 4-pin floppy
Antec EarthWatts 500W 20/24-pin 4-pin, 8-pin 2 x 6-pin 6 4 1
Antec Neo HE 550W 20/24-pin 4-pin, 8-pin 2 x 6-pin 6 41 22
Antec TruePower Trio 650W 20/24-pin 4-pin, 8-pin 2 x 6-pin 83 4 1
Cooler Master Real Power Pro 550W 24-pin 4-pin, 8-pin 2 x 6-pin 5 6 1
Cooler Master Real Power Pro 650W 24-pin 4-pin, 8-pin 2 x 6-pin 5 6 1
Corsair HX 620W 20/24-pin 4-pin, 8-pin 2 x 6/8-pin,
2 x 6-pin
10 84 22
Enermax Infiniti 720W 24-pin 4/8-pin 6/8-pin,
2 x 6-pin
9 9 22
OCZ GameXStream 700W 20/24-pin 4/8-pin 2 x 6-pin 6 6 2
PC Power & Cooling Silencer 750W 24-pin 4-pin, 8-pin 2 x 6/8-pin,
2 x 6-pin
8 6 1
Seasonic S12II 500W 20/24-pin 4-pin, 8-pin 6/8-pin,
9 6 22
ThermalTake Toughpower 700W 20/24-pin 4/8-pin 6/8-pin,
2 x 6-pin
7 6 2
1. Two of the Neo HE's four SATA plugs are on an extra lead that can only be used at the expense of leads for one of the PCIe connectors or three peripheral connectors.
2. Floppy connectors come on an adapter that consumes one peripheral connector.
3. Two of the TruePower's eight peripheral connectors can only be used with system fans.
4. Five of the HX's eight SATA plugs are on a pair of extra leads that will cost you two peripheral connectors each.

Each power supply in this round-up is equipped with a 24-pin primary power connector, but only six of those connectors can also be used with older 20-pin motherboards. We also see some variation when it comes to auxiliary 12V power connectors. All the power supplies are equipped to provide 4- or 8-pin auxiliary 12V power, but some do so with a hybrid connector, while others opt for individual 4- and 8-pin plugs.

A hybrid 8/6-pin PCIe connector next to a standard 6-pin plug
Be careful not to confuse 12V connectors with the new 8-pin PCIe connectors. The power requirements of high-end graphics cards have eclipsed the capacity of traditional 6-pin PCIe connectors, and just about half of the PSUs we've assembled feature at least one 8-pin PCIe connector. In each case, that 8-pin connector is a hybrid design that can also be converted for use with graphics cards that have 6-pin connectors.

Interestingly, only two units in this litter are properly equipped for high-end CrossFire configurations: the Corsair HX 620W and the "CrossFire Edition" of PC Power & Cooling's Silencer 750W. The rest all have at least two 6-pin PCIe connectors, which is enough for most high-end graphics cards.

Update 10/05/2007 — Cooler Master has bumped the warranty coverage of its Real Power Pro power supplies to five years.