Running the numbers
Our Chroma load-testing procedures can be found at this link.
Efficiency
| Load | 10% | 25% | 50% | 75% | 100% |
|---|---|---|---|---|---|
| Efficiency | 82.6% | 90.1% | 92% | 90.8% | 90.2% |
There's very little to separate the best 80 PLUS Gold-rated supplies from vastly more expensive 80 PLUS Platinum models. EVGA's performance is at the upper end of 80 PLUS Gold.
Regulation
In terms of regulation, we're looking at just how well the supply is able to hold to the various lines. The ATX spec. has a +/- 5 per cent leeway on all but the -12V line.
| Line/Load | 3.3V | 5V | 12V |
|---|---|---|---|
| 10 per cent | +0.3% | +0.9% | +1.2% |
| 50 per cent | -0.1% | +0.5% | +0.8% |
| 100 per cent | -0.8% | -0.2% | 0% |
Having looked at PSUs in detail for a number of years, manufacturing quality has improved such that very few supplies do poorly here. Near-server-grade performance is now readily available for a reasonable outlay.
Regulation - cross-load
How about providing uneven loads that stress particular voltage rails? In the first attempt, we've put 60A on the 12V rails, and 1A on the 3.3V and 5V rails. This can actually be somewhat typical for a system heavy on graphics and CPU power. In the second, we've turned the tables and gone for 12A on both the 3.3V and 5V rails - highly unlikely in a real-world environment - and just 2A on the 12V - even more unlikely!
| Line/Load | 3.3V | 5V | 12V |
|---|---|---|---|
| Cross-load 12V focus | +0.8% | +1.1% | -0.6% |
| Cross-load 3.3V/5V focus | -1.3% | -0.6% | +1.7% |
Hammering one part of the PSU power delivery while using just a small portion of the other can throw cheaper supplies out of kilter. Numbers stack up nicely against the non-cross-load tests, which is a hallmark of a premium, top-quality supply.
What does this really mean? You'll never see large voltage drops, which can lead to instability, when the PC is loaded up.
Ripple
| Line/Load (mv - p-p max) | 3.3V | 5V | 12V |
|---|---|---|---|
| 10 per cent | 10mV | 10mV | 15mV |
| 50 per cent | 15mV | 15mV | 30mV |
| 100 per cent | 20mV | 25mV | 35mV |
The ATX v2.2 spec states that the maximum permissible ripple is 120mV for the 12V line and 50mV for others.
PSUs convert AC power into DC, but doing so requires the AC waveform to be suppressed. What we're really testing here is the quality of the supply's rectifier and any smoothing capacitors in getting rid of this unwanted up-and-down ripple. Performance is comfortably within the limits of the specification.
Temps
| Temperatures | Intake | Exhaust |
|---|---|---|
| 10 per cent | 27°C | 34°C |
| 50 per cent | 36°C | 42°C |
| 100 per cent | 38°C | 45°C |
We've tested the temperature with the ECO switch disabled. The figures are just above average for a supply of this ilk. Activating ECO, however, results in the fan being off until about 330W.
Fan performance
Temps are good but they mean little in isolation. Obtaining accurate noise readings is near-on impossible when the supply is connected to the Chroma test harness and dual-unit load-tester. We can test the manufacturer's quietness claims in a different way, by using an AMPROBE TMA10A anemometer placed directly over the centre of the PSU. The anemometer records the airflow being pushed/pulled from the PSU's fan. We can use a Voltcraft DT-10L RPM meter to measure the rotational speed of the fan, too.
| Load | Fan RPM | Airflow | Noise |
|---|---|---|---|
| 10 per cent | 500rpm | circa-15cfm | Very quiet |
| 50 per cent | 700rpm | circa-25cfm | Very quiet |
| 100 per cent | 1,500rpm | circa-50cfm | Noticeable, not annoying |
The fan can't be heard at a mid-load 375W. Putting this into context, our GTX 780 Ti-based gaming system draws less than this when playing games.
