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PSU Roundup: Performance, Price, Efficiency
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1. Mainstream PSUs Up To 700W

It’s been a while since our last large power supply test. Nowadays, almost all manufacturers label their power supplies with the 80 PLUS logo (for more information on 80 PLUS and what the branding actually means, check out the organization’s site. Energy efficiency has become essential to both vendors and users.

But other characteristics also play a more critical role now. Today’s power supplies include more flexibility than ever before. In addition to the familiar fan control, power consumption display, and cable management system, you’ll sometimes find USB ports and chic accessory bags. But what features—and what fundamental specifications—do you really need ?

Our German lab recently tested 10 current mainstream power supplies with power delivery of up to 700 watts. In part one (this one) we introduce the first five products. Look for part two shortly, when we’ll discuss the next five.

ManufacturerPower Supply
Cooler Master Silent Pro M500
Thermaltake Toughpower QFan 650W
Silverstone SST-ST70F Strider
Antec Signature
Dragon Force DF-530GT

In part two, we test the following products :

Manufacturer Power Supply
PC Power & Cooling Silencer 610 W
Hiper Type R MK2 680 W
Enermax Modu 82+
Fortron FSP Everest 600 W
Tagen TG680 U33II
Corsair HX 520W
2. First Up: Cooler Master Silent Pro 500 Watt

The Silent Pro series from Cooler Master consists of three models ranging from 500 watts to 700 watts. For our test, Cooler Master sent its 500 watt offering.

Unlike competing PSUs, the Silent Pro power supplies includes its own form of cable management—you’ll immediately notice the flat black cables, which are much easier to tuck out of the way than the thinner, rounded bundles typical of high-end PSUs.

At first glance, the cables appear unexciting, but they offer tremendous advantages: to begin, the cords are extremely flexible and allow you to connect devices without putting tension on the cords, which would then also put pressure on the ports. This innovation eliminates the common concern about SATA power connectors when attaching hard drives using power supplies with stiff cords.

3. Cooler Master Silent Pro 500 Watt (Continued)

The cable management connector sockets are labeled, and they’re shaped so they can’t be plugged in incorrectly. The five-pin sockets are designed so that you can attach modular 4-pin Molex and SATA cables as needed. The 6-pin sockets are for auxiliary PCI Express graphics cables.

The power supply is cooled by a 140 mm fan on the underside. The warm air is exhausted through a breadboard on the back. The fan is controlled automatically by the power supply according to operating temperature—no need for manual adjustment.

The maximum power is, as advertised, 500 watts. The maximum combined load on the 5 V and 3.3 V rails is 145 watts.

This one seems to be more widely available in Europe—none of our favorite online vendors seem to be stocking it yet .

4. Voltage

Voltage at 100% Load
Nominal ValueMeasurementsAllowed Deviation
3.3 Volt3.23 Volt3.14 Volt to 3.47 Volt
5 Volt4.86 Volt4.75 Volt to 5.25 Volt
12 Volt12.20 Volt11.40 Volt to 12.60 Volt
12 Volt (CPU)12.17 Volt11.40 Volt to 12.60 Volt
5 Volt (Standby)4.94 Volt4.75 Volt to 5.25 Volt
-12 Volt-11.93 Volt-10.80 Volt to 13.20 Volt

Voltage at 50% Load
Nominal ValueMeasurementsAllowed Deviation
3.3 Volt3.29 Volt3.14 Volt to 3.47 Volt
5 Volt4.94 Volt4.75 Volt to 5.25 Volt
12 Volt12.24 Volt11.40 Volt to 12.60 Volt
12 Volt (CPU)12.23 Volt11.40 Volt to 12.60 Volt
5 Volt (Standby)4.99 Volt4.75 Volt to 5.25 Volt
-12 Volt-11.72 Volt-10.80 Volt to -13.20 Volt

Voltage at 20% Load
Nominal ValueMeasurementsAllowed Deviation
3.3 Volt3.33 Volt3.14 Volt to 3.47 Volt
5 Volt5.01 Volt4.75 Volt to 5.25 Volt
12 Volt12.23 Volt11.40 Volt to 12.60 Volt
12 Volt (CPU)12.22 Volt11.40 Volt to 12.60 Volt
5 Volt (Standby)5.01 Volt4.75 Volt to 5.25 Volt
-12 Volt-11.53 Volt-10.80 Volt to -13.20 Volt

5. Efficiency

The power supplies we’ve seen from Cooler Master have relatively high efficiency. However, the Silent Pro is a bit disappointing. Instead of remaining at the top, the Cooler Master unit ends up somewhere in the middle of our pack; it gets close to 87 percent efficiency but doesn’t quite make it. Therefore, the efficiency at low loads of 85.3 percent doesn’t drop as much as it might if our 50% load numbers were higher. Under maximum load, the PSU reaches almost 84 percent.

Very surprising, however, is the standby power consumption: a mere 0.35 watts—the best among the products we tested. This is the draw taken from the connection socket when there is no load. When the load increases to 2.5 watts, the power consumption remains good, at 4.12 watts.

Cooler Master Silent Pro 500
The power supply offers acceptable performance for the price. The flexible cables make wiring a much simpler proposition, which we like.

  • Positives
  • Negatives
    • Flat, flexible wires
    • Lots of connectivity
    • Low standby energy consumption
    • Relatively low efficiency
    • Cords aren’t color coded

6. Thermaltake Toughpower QFan 650W

Thermaltake promises robust power, hence the name “Toughpower.” We tested the 650 watt version of the QFan series.

The white fan keeping the power supply cool is fairly large at 140 mm, and it spins somewhat slowly due to its size. This is good news—lower RPMs translate to less noise output. The fan intake in the housing is designed to improve air supply even as acoustics remain manageable.

The power supply provides its own form of cable management. The SATA and 4-pin Molex connectors, as well as the PCIe cords, can be plugged into the power supply’s available 6-pin receptacles. They’re pinned differently, making it impossible to connect them incorrectly.

7. Thermaltake Toughpower QFan 650W (Continued)

At the three load levels (low, medium and high), the voltages are within the allowed deviations.

However, the situation changes dramatically at low loads. If the current on the 12-volt lines drops below 1 amp, the voltage on the 5 volt line decreases drastically. At a load of 0.42 amps, we measure only 4.03 volts (minimum value according to specification is 4.75 volts). At even lower loads the voltage drops to 3.8 volts. This is clearly a malfunction. The manufacturer has not yet responded to this concern.

Due to these issues, the Low-Power PC Test could not be performed.

The power supply can be purchased online for right around $150.

8. Voltage

Voltage at 100% Load
Nominal ValueMeasurementsAllowed Deviation
3.3 Volt3.21 Volt3.14 Volt to 3.47 Volt
5 Volt4.98 Volt4.75 Volt to 5.25 Volt
12 Volt11.94 Volt11.40 Volt to 12.60 Volt
12 Volt (CPU)11.72 Volt11.40 Volt to 12.60 Volt
5 Volt (Standby)5.04 Volt4.75 Volt to 5.25 Volt
-12 Volt-12.37 Volt-10.80 Volt to -13.20 Volt

Voltage at 50% Load
Nominal ValueMeasurementsAllowed Deviation
3.3 Volt3.28 Volt3.14 Volt to 3.47 Volt
5 Volt5.03 Volt4.75 Volt to 5.25 Volt
12 Volt12.01 Volt11.40 Volt to 12.60 Volt
12 Volt (CPU)11.90 Volt11.40 Volt to 12.60 Volt
5 Volt (Standby)5.09 Volt4.75 Volt to 5.25 Volt
-12 Volt-12.10 Volt-10.80 Volt to -13.20 Volt

Voltage at 20% Load
Nominal ValueMeasurementsAllowed Deviation
3.3 Volt3.32 Volt3.14 Volt to 3.47 Volt
5 Volt5.06 Volt4.75 Volt to 5.25 Volt
12 Volt12.05 Volt11.40 Volt to 12.60 Volt
12 Volt (CPU)12.03 Volt11.40 Volt to 12.60 Volt
5 Volt (Standby)5.12 Volt4.75 Volt to 5.25 Volt
-12 Volt-11.97 Volt-10.80 Volt to -13.20 Volt

9. Efficiency

Efficiency-wise, Thermaltakes’ power supply falls into the middle of the pack. Its most promising value is at medium load—a respectable 86 percent. At full and low loads, it’s about 84 percent.

In standby mode the device consumes 1.4 watts. At a load of 2.5 watts it uses 4.90 watts. We think that these results could be better.

Thermaltake Toughpower QFan 650
In normal operation, the power supply shows good results. However, at low load the device is outside the specifications and therefore doesn’t pass.
  • Positives
  • Negatives
    • Good Ventilation Concept
    • 5 volt line at low load is outside the specifications

10. Silverstone SST-ST70F Strider 700W

Silverstone sent its 700-watt SST-ST70F Strider to our test course. Although the power supply arrived in fairly unassuming packaging, the unit itself features good cable management system and plenty of cables for attaching peripherals.

The power supply comes with all its lines plugged in by default. The SST-ST70F is the only modular power supply in the test field where you can literally remove the lines—including the processor power supply and the ATX cable.

The removable nature of the ATX cable doesn’t make sense because you can’t run a power supply without its ATX line, but it lets you get the stiff ATX cable out of the way when you want to remove other components from the small device.

11. Silverstone SST-ST70F Strider (Continued)

The design of the cables themselves warrants our recognition. A plastic mesh coats the long part of the cable up to the first plug. The rest of the cable is held together with a plastic wire strip. This simplifies installation and eliminates concern about breaking a connector on the hard drive during installation.

In addition to six SATA and six Molex plugs, you’ll find two floppy connectors on the included cables. The power supply also comes with four PCIe plugs as well as 4- and 8-pin processor connectors—all on separate lines. The ATX plug is seperate.

This power supply is available online for right around $139.

12. Voltage

Voltage at 100% Load
Nominal ValueMeasurementsAllowed Deviation
3.3 Volt3.17 Volt3.14 Volt to 3.47 Volt
5 Volt4.78 Volt4.75 Volt to 5.25 Volt
12 Volt12.14 Volt11.40 Volt to 12.60 Volt
12 Volt (CPU)11.88 Volt11.40 Volt to 12.60 Volt
5 Volt (Standby)4.83 Volt4.75 Volt to 5.25 Volt
-12 Volt-12.47 Volt-10.80 Volt to -13.20 Volt

Voltage at 50% Load
Nominal ValueMeasurementsAllowed Deviation
3.3 Volt3.27 Volt3.14 Volt to 3.47 Volt
5 Volt4.97 Volt4.75 Volt to 5.25 Volt
12 Volt12.18 Volt11.40 Volt to 12.60 Volt
12 Volt (CPU)12.06 Volt11.40 Volt to 12.60 Volt
5 Volt (Standby)4.94 Volt4.75 Volt to 5.25 Volt
-12 Volt-12.04 Volt-10.80 Volt to -13.20 Volt

Voltage at 20% Load
Nominal ValueMeasurementsAllowed Deviation
3.3 Volt3.33 Volt3.14 Volt to 3.47 Volt
5 Volt5.11 Volt4.75 Volt to 5.25 Volt
12 Volt12.13 Volt11.40 Volt to 12.60 Volt
12 Volt (CPU)12.11 Volt11.40 Volt to 12.60 Volt
5 Volt (Standby)5.00 Volt4.75 Volt to 5.25 Volt
-12 Volt-11.68 Volt-10.80 Volt to -13.20 Volt

13. Efficiency

Silverstone, the winner in many of our previous efficiency tests, seems to be resting on its laurels. This time around, it lands in last place. Let’s look at the numbers:

Under full load, the Strider’s efficiency is 82.2 percent. At half-load it’s a bit better—Silverstone ends up in the midfield with 86.5 percent. The SST-ST70F truly looks good only at low load, where the power supply outperforms its competitors with 86.7 percent.

This trend continues as the load falls. In our low-power comparison at 35 watts, the Silverstone power supply performs best in the test field with more than 78 percent. But if you’re a low-power user, you’re probably not in the market for a 700 watt power supply, so it’s a bit of a catch 22.

The result for standby is average. At zero load the Strider consumes 1.17 watts; at a load of 2.5 watts it needs 4.57 watts.

Silverstone SST-ST70F
The power supply from Silverstone combines high performance with good cable management, long cables, and many plugs.
  • Positives
  • Negatives
    • Many peripheral plugs
    • Long cables
    • Good efficiency at low load
    • Low efficiency at full load

14. Antec Signature 650W

The chic packaging for Antec’s Signature power supply is certainly eye-catching. The power supply and its accessories are elegantly organized. This is one of the few power supplies that ia still cooled via conventional means (with the fan on the back)—that allows for use on flat server or HTPC housings.

An included test report from Antec gives us some additional detail about the ATX specification.

15. Antec Signature (Continued)

The power supply is partially modular. The ATX, processor, SATA, and Molex plugs are connected directly to the body of the supply. Extension cables are available for the SATA and Molex plugs.

Antec is the only manufacturer to provide more cables than can be plugged in simultaneously. As a result, the user can choose whether to use more SATA or more Molex cables. The additional cables are labeled with the letter O (Optional) in the cable list.

The voltages are always within the allowed specifications. However, under full load, the voltages on the 3.3 volt and 5 volt lines drop slightly.

Naturally, all of Antec’s niceties come at a price. You can expect to pay just over $200 for this 650 W power supply online.

16. Voltages

Voltage at 100% Load
Nominal ValueMeasurementsAllowed Deviation
3.3 Volt3.17 Volt3.14 Volt to 3.47 Volt
5 Volt4.89 Volt4.75 Volt to 5.25 Volt
12 Volt11.89 Volt11.40 Volt to 12.60 Volt
12 Volt (CPU)11.81 Volt11.40 Volt to 12.60 Volt
5 Volt (Standby)4.88 Volt4.75 Volt to 5.25 Volt
-12 Volt-12.03 Volt-10.80 Volt to -13.20 Volt

Voltage at 50% Load
Nominal ValueMeasurementsAllowed Deviation
3.3 Volt3.27 Volt3.14 Volt to 3.47 Volt
5 Volt4.97 Volt4.75 Volt to 5.25 Volt
12 Volt12.05 Volt11.40 Volt to 12.60 Volt
12 Volt (CPU)12.02 Volt11.40 Volt to 12.60 Volt
5 Volt (Standby)4.94 Volt4.75 Volt to 5.25 Volt
-12 Volt-11.97 Volt-10.80 Volt to -13.20 Volt

Voltage at 20% Load
Nominal ValueMeasurementsAllowed Deviation
3.3 Volt3.32 Volt3.14 Volt to 3.47 Volt
5 Volt5.01 Volt4.75 Volt to 5.25 Volt
12 Volt12.08 Volt11.40 Volt to 12.60 Volt
12 Volt (CPU)12.07 Volt11.40 Volt to 12.60 Volt
5 Volt (Standby)4.97 Volt4.75 Volt to 5.25 Volt
-12 Volt-11.93 Volt-10.80 Volt to -13.20 Volt

17. Efficiency

Antec’s power supply shows remarkable efficiency under full load as well as half load. It’s able to demonstrate 87.2 percent and 88 percent, respectively. Under low load, efficiency drops slightly to 83.3 percent. Just bear in mind that under full load, this is the best device in our test field.

The power supply is frugal in standby, too. It uses 690 milliwatts at zero load. At a load of 2.5 watts on the standby cable it consumes 4 watts, an efficiency of 62 percent. Antec’s voltage converter does relatively well with this result, too.

Antec Signature 650 Watt
The Antec power supply is the classic size and is thus well-suited to use in 19-inch and HTPC housings.
  • Positives
  • Negatives
    • Fan design is ideal for HTPCs.
    • Low energy need in standby
    • Higher efficiency
    • Choice options with Molex and SATA
    • Higher price
18. Dragon Force DF-530GT

The DF-530GT is the least expensive power supply we tested (roughly 40 euro), though again, this is one of those units readily available in Europe and Asia, but not so much in North America. Clearly, you won’t get any special features for such a low price—this power supply has a straightforward design with no cable management.

The connection options are merely sufficient for today’s systems. For graphics cards, there is a 6- and an 8-pin plug PCI Express auxiliary power plug, which can be broken off into a second 6-pin connector. For the processor power cord, there’s only a 4-pin plug—you’ll have to use an adapter for boards that require an 8-pin connector. The ATX plug has 24 pins and is not separable.

19. Dragon Force DF-530GT (Continued)

The Dragon Force includes only three SATA plugs, three Molex plugs and one floppy connector. Needless to say, it’s a little light in the connectivity department.

The 120 mm fan has three settings: low-speed is silent, high-speed is high-performance, and standard adjusts speed automatically depending on the temperature.

The power supply delivers the needed power without a problem. The voltages are always within the allowed deviation and very stable—even under full load they hardly differ from the nominal values.

20. Voltages

Voltage at 100% Load
Nominal ValueMeasurementsAllowed Deviation
3.3 Volt3.21 Volt3.14 Volt to 3.47 Volt
5 Volt4.92 Volt4.75 Volt to 5.25 Volt
12 Volt11.92 Volt11.40 Volt to 12.60 Volt
12 Volt (CPU)11.93 Volt11.40 Volt to 12.60 Volt
5 Volt (Standby)5.06 Volt4.75 Volt to 5.25 Volt
-12 Volt-12.22 Volt-10.80 Volt to -13.20 Volt

Voltage at 50% Load
Nominal ValueMeasurementsAllowed Deviation
3.3 Volt3.25 Volt3.14 Volt to 3.47 Volt
5 Volt4.97 Volt4.75 Volt to 5.25 Volt
12 Volt12.10 Volt11.40 Volt to 12.60 Volt
12 Volt (CPU)12.09 Volt11.40 Volt to 12.60 Volt
5 Volt (Standby)5.10 Volt4.75 Volt to 5.25 Volt
-12 Volt-11.99 Volt-10.80 Volt to -13.20 Volt

Voltage at 20% Load
Nominal ValueMeasurementsAllowed Deviation
3.3 Volt3.32 Volt3.14 Volt to 3.47 Volt
5 Volt5.03 Volt4.75 Volt to 5.25 Volt
12 Volt12.14 Volt11.40 Volt to 12.60 Volt
12 Volt (CPU)12.14 Volt11.40 Volt to 12.60 Volt
5 Volt (Standby)5.13 Volt4.75 Volt to 5.25 Volt
-12 Volt-11.82 Volt-10.80 Volt to -13.20 Volt

21. Efficiency

The Dragon Force’s efficiency is very high relative to its price. At mid-load, the power supply has an excellent efficiency of almost 88 percent. This drops to 84 percent at maximum load, but even under low load the DF-530GT gets a good result of 85.5 percent.

The Dragon Force also does well in the Low-Power PC Test. Its efficiency drops to 76 percent at a 35-watt load, but that’s still extremely high compared with competitors.

In standby mode without load, we measured 1.14 watts out of the socket. Here, some competitors consume significantly less. At standby load it consumes about 4.86 watts, an efficiency of 51 percent. At this level, the power supply is in the middle of the pack.

Dragon Force DF-530GT
Straightforward power supply without special features for an inexpensive price.
  • Positives
  • Negatives
    • Very low price
    • No cable management
    • Short cables with few sockets

22. Charts: Efficiency Specifications

23. Charts: Efficiency @ 250 Watts, 35 Watts, And Standby

24. Conclusion: Dragon Force and Silverstone Win

The clear “performance for your money” winner in our power supply test is the Dragon Force. The DF-530GT is a solid device that delivers its performance without any issues, running on stable voltages that never deviate much from the nominal values. But you don’t get everything for this low price, of course. There’s no cable management, no accessories, and few cables are included. More problematic for North American customers is availability. Unfortunately, this unit will likely only be an option for our overseas readers.

Thus, our overall recommendation for this round (and Best of Tom’s award) goes to Silverstone’s Strider SST-ST70F. Priced at about $139, this power supply is unbeatable given its performance. It also comes with many long connection cables, which simplify configuration in component-laden PCs and eliminate the need for add-on adapters. Although the Silverstone’s efficiency drops under full load, it remains very high under half-load and low-load conditions.