Testing results
Our testing procedures can be found at this link.
Efficiency
| Load | 10pc | 25pc | 50pc | 75pc | 100pc |
|---|---|---|---|---|---|
| Efficiency | 83.3pc | 90.4pc | 93.2pc | 88.1pc | 87.5pc |
Keeping fan noise at a minimum requires that the supply have a high efficiency figure. The sample CS550M manages to hit 90 per cent-plus across the kind of load that a modern system would push out. As a point of reference, a Core i7-4770K and GTX 780 Ti system pulls, at the wall, around 300W, thus hitting the efficiency sweetspot for this model.
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 | +1.2pc | +1.7pc | +2.4pc |
| 50 per cent | +0.5pc | +0.8pc | +1.6pc |
| 100 per cent | -2.2pc | -0.3pc | +1.0pc |
Most supplies overvolt with little load and undervolt when stressed. There's nothing out of the ordinary here; Platinum-rated supplies, costing rather more, tend to have better regulation, but we're happy with the results from the Corsair.
Regulation - cross-load
How about providing uneven loads that stress particular voltage rails? In the first attempt, we've put 40A 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 | -1.5pc | +0.8pc | +1.7pc |
| Cross-load 3.3V/5V focus | -1.7pc | +1.2pc | +2.0pc |
Hammering one part of the PSU power delivery while using just a small portion of the other can throw cheaper supplies of out kilter. The hallmark of a solid supply is little variation at the extremes of load - the 550W model's performance is well within parameters.
Ripple
| Line/Load (mv - p-p max) | 3.3V | 5V | 12V |
|---|---|---|---|
| 10 per cent | 10mV | 15mV | 15mV |
| 50 per cent | 25mV | 20mV | 20mV |
| 100 per cent | 30mV | 30mV | 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.
Do bear in mind that we've yet to see a PSU fall outside the specification demanded by the ATX standard.
Temps
| Temperatures | Intake | Exhaust |
|---|---|---|
| 10 per cent | 29°C | 35°C |
| 50 per cent | 34°C | 43°C |
| 100 per cent | 40°C | 47°C |
With no silent-fan mode at low loads, temperatures are good. The unit does become warmer as the heatsinks and fan are stressed, but, again, the supply works just fine at 100 per cent load.
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-20cfm | Very quiet |
| 50 per cent | 700rpm | circa-25cfm | Very quiet |
| 100 per cent | 900rpm | circa-50cfm | Quiet |
Though obviously not silent at low loads unlike its RM brethren, you would struggle to hear the fan when housed inside a chassis - the CPU, graphics and case fans would, we believe, drown out the sound produced by the 120mm spinner in the PSU.
