Running the numbers
Our Chroma load-testing procedures can be found at this link.
Efficiency
| Load | 10pc | 25pc | 50pc | 75pc | 100pc |
|---|---|---|---|---|---|
| Efficiency | 87.0pc | 90.9pc | 92.8pc | 91.3pc | 90.2pc |
As you would expect, efficiency is top-notch right across the load spectrum, busting through the 90 per cent barrier at all but 10 per cent. Actually, the most-impressive figure is the low-load test's; it's difficult for a supply to offer super-high efficiencies at miniscule loads.
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 | +0.8pc | +0.6pc | +0.7pc |
| 50 per cent | +0.2pc | +0.3pc | +0.6pc |
| 100 per cent | -0.7pc | -0.1pc | -0.4pc |
We don't see an instance of where the supply is more than one per cent off the mark: impressive stuff.
Regulation - cross-load
How about providing uneven loads that stress particular voltage rails? In the first attempt, we've put 80A 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 | +0.9 | +1.0pc | -0.6pc |
| Cross-load 3.3V/5V focus | -1.8pc | -1.0pc | +0.9pc |
Hammering one part of the PSU power delivery while using just a small portion of the other can throw cheaper supplies of out kilter. There's not a huge amount of variation going on here; you're looking at less than three per cent from a best-to-worst-case scenario.
Ripple
| Line/Load (mv - p-p max) | 3.3V | 5V | 12V |
|---|---|---|---|
| 10 per cent | 15mV | 10mV | 15mV |
| 50 per cent | 15mV | 15mV | 20mV |
| 100 per cent | 28mV | 18mV | 30mV |
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.
Per-line ripple is comfortably less than half of what the ATX specification permits. The 12V ripple at full load is usually the worst figure, with AC suppression being hardest to control under this load, but the figure here is as good as any we've seen from a high-end PSU.
Temps
| Temperatures | Intake | Exhaust |
|---|---|---|
| 10 per cent | 27°C | 38°C |
| 50 per cent | 33°C | 35°C |
| 100 per cent | 35°C | 42°C |
The fan isn't activated until the load hits 40 per cent and this is why the PSU is actually cooler at 50 per cent load than at 10 per cent. The supply was tested with an ambient temperature of 28°C, which is around 5°C higher than most other supplies we have looked at in the preceding four months.
Noise
As advertised, the supply is silent at low loads. However, just like the HX850, the auto-switching mechanism isn't exact. We loaded the supply with 600W for five minutes and then reduced this to 100W, a figure where the fan should be switched off. The unit took approximately 20 seconds to determine it was safe to switch the fan off completely. Unlike the HX850, running from 100W up to 600W makes the fan kick-in faster.
Silent at any load up to 500W and then gradually increasing the RPM until the fan becomes noticeable at around 800W, you really need to push it to know a fan is in the PSU chassis.
