Enermax Eco80+ 500W PSU

TESTING

For a fuller understanding of ATX power supplies, please read the reference article Power Supply Fundamentals. Those who seek source materials can find Intel's various PSU design guides at Form Factors.

For a complete rundown of testing equipment and procedures, please refer to SPCR's PSU Test Platform V4.1. The testing system is a close simulation of a moderate airflow mid-tower PC optimized for low noise.

Acoustic measurements are now performed in our anechoic chamber with ambient level of 11 dBA or lower, with a PC-based spectrum analyzer comprised of SpectraPLUS software with ACO Pacific microphone and M-Audio digital audio interfaces.

In the test rig, the ambient temperature of the PSU varies proportionately with its output load, which is exactly the way it is in a real PC environment. But there is the added benefit of a high power load tester which allows incremental load testing all the way to full power for any non-industrial PC power supply. Both fan noise and voltage are measured at various standard loads. It is, in general, a very demanding test, as the operating ambient temperature of the PSU often reaches >40°C at full power. This is impossible to achieve with an open test bench setup.

The 120mm fan responsible for "case airflow" is deliberately run at a steady low level (6~7V) when the system is run at "low" loads. When the test loads become greater, the 120mm fan is turned up to a higher speed, but one that doesn't affect the noise level of the overall system. Anyone who is running a system that draws 400W or more would definitely want more than 20CFM of airflow through their case, and at this point, the noise level of the exhaust fan is typically not the greatest concern.

Great effort has been made to devise as realistic an operating environment for the PSU as possible, but the thermal and noise results obtained here still cannot be considered absolute. There are too many variables in PCs and too many possible combinations of components for any single test environment to provide infallible results. And there is always the bugaboo of sample variance. These results are akin to a resume, a few detailed photographs, and some short sound bites of someone you've never met. You'll probably get a pretty good overall representation, but it is not quite the same as an extended meeting in person.

REAL SYSTEM POWER NEEDS: While we test the PSU to full output in order to verify the manufacturer's claims, real desktop PCs simply do not require anywhere near this level of power. The most pertinent range of DC output power is between about 40W and 300W, because it is the power range where most systems will be working most of the time. To illustrate this point, we conducted system tests to measure the power draw of several actual systems under idle and worst-case conditions. Our most power-hungry overclocked 130W TDP processor rig with an ATI Radeon X1950XTX-512 graphics card drew ~256W DC peak from the power supply under full load — well within the capabilities of any modern power supply. Please follow the link provided above to see the details. It is true that very elaborate systems with the most power hungry dual video cards today might draw as much as another 150~200W, but the total should remain under 500W in extrapolations of our real world measurements.

INTERPRETING TEMPERATURE DATA

It important to keep in mind that PSU fan speed varies with temperature, not output load. A power supply generates more heat as output increases, but this is not the only factor that affects fan speed. Ambient temperature and case airflow have almost as much effect. Our test rig represents a challenging thermal situation for a power supply: A large portion of the heat generated inside the case must be exhausted through the power supply, which causes a corresponding increase in fan speed.

When examining thermal data, the most important indicator of cooling efficiency is the difference between intake and exhaust. Because the heat generated in the PSU loader by the output of the PSU is always the same for a given power level, the intake temperature should be roughly the same between different tests. The only external variable is the ambient room temperature. The temperature of the exhaust air from the PSU is affected by several factors:

The thermal rise in the power supply is really the only indicator we have about all of the above. This is why the intake temperature is important: It represents the ambient temperature around the power supply itself. Subtracting the intake temperature from the exhaust temperature gives a reasonable gauge of the effectiveness of the power supply's cooling system. This is the only temperature number that is comparable between different reviews, as it is unaffected by the ambient temperature.

TEST RESULTS

The ambient temperature was 23°, and the ambient noise level was 11 dBA. AC input voltage was 118~121V.

1. EFFICIENCY — This is a measure of AC-to-DC conversion efficiency. The ATX12V Power Supply Design Guide recommends 80% efficiency or better at all output power loads. 80% efficiency means that to deliver 80W DC output, a PSU draws 100W AC input, and 20W is lost as heat within the PSU. Higher efficiency is preferred for reduced energy consumption and cooler operation. It allows reduced cooling airflow, which translates to lower noise. The 80 Plus standard requires a minimum of 80% efficiency at 20%, 50%, and 100% of the rated maximum load.

There was a time when 80% efficiency at 90W output and above would have been top notch performance. No more — with the latest power 80 Plus Gold power supplies breaching 90% regularly, an 84% peak efficiency is a bit of a yawn. It merits basic 80 Plus certification, but does not meet any of the higher standards.

That said, it's helpful to put things in perspective. At 200W output (above the maximum power usage for most normal systems), the AC power consumption difference between the Eco80+ and the record-breaking Seasonic X-650 is 20W. That's not nothing, but it's not a whole lot either. That 20 watts is likely more important in what it means for cooling (and thus noise and reliability) than what it means to the environment.

2. DC VOLTAGE REGULATION refers to how stable the output voltages are under various load conditions. The ATX12V Power Supply Design Guide calls for the +12, +5V and +3.3V lines to be maintained within ±5%.

Unless a unit goes into overload, it's rare that we see significant problems with voltage regulation. The Eco80+ is no exception — it was nearly always within ±2% and it never exceeded ±3% on any line. With the exception of the cross-load test (which is strenuous), the +12V line stayed above the specified +12V at all times.

3. AC RIPPLE refers to unwanted "noise" artifacts in the DC output of a switching power supply. It's usually very high in frequency (in the order of 100s of kHz). The peak-to-peak value is measured. The ATX12V Guide allows up to 120mV (peak-to-peak) of AC ripple on the +12V line and 50mV on the +5V and +3.3V lines. Where voltage regulation is a measure of variance from spec, ripple is more a measure of tolerance: How much the voltage is changing at any given time. Ripple is of interest to over- and under-clockers who push their systems to the limits of what they are actually capable of rather than relying on what the specs say they should be capable of.

Ripple on the Eco80+ was generally around 20 mV on all lines, and it changed very little as load increased. These are good numbers — well within spec — the lack of change as the load was increased is a good sign.

4. POWER FACTOR is ideal when it measures 1.0. In the most practical sense, PF is a measure of how "difficult" it is for the electric utility to deliver the AC power into your power supply. High PF reduces the AC current draw, which reduces stress on the electric wiring in your home (and elsewhere up the line). It also means you can do with a smaller, cheaper UPS backup; they are priced according to their VA (volt-ampere) rating.

As is the case for most units with active power factor correction (which, these days, is most reputable brands), PFC was close to perfect, starting at 0.91 for the minuscule 20W load, and staying at 0.98 and above through most of the common operating range.

5. LOW LOAD TESTING revealed no problems starting at very low loads and it stayed operational with no load applied. The low 6.1W baseline power consumption is reflected in the relatively high efficiency at low loads where the baseline "overhead" makes up a proportionally larger amount of the power lost to heat.

6. TEMPERATURE & COOLING

The thermal design of the Eco80+ is probably its weakest point. While we saw no signs that temperature was a problem for stability, the thermal rise was higher that we would like. This is probably tied to the speed of the fan, since the temperature rise was very sensitive to changes in fan speed, suggesting that the fan controller did a good job of keeping the fan speed right on the edge of the threshold needed to evacuate heat adequately.

This is an engineering tradeoff. Low fan speed means low noise — something we wholeheartedly approve of. And, so long as the internal components are of high quality and heat tolerance, a higher thermal rise at low loads is not a bad thing. Judging by the rest of the performance numbers, component quality should not be an issue. Just don't count on the Eco80+ to remove a lot of heat from your system; this is standard advice for anyone using a quiet PSU.

At higher loads (>400W) it's a different story. Once the thermal rise hits ~15°C or more, there is cause for concern, especially if the power supply is likely to see long term stress at these levels. The situations where this actually happens are few and far between, but we don't recommend using this power supply with multiple graphics cards.