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Review: Corsair AX1200i Digital ATX Power Supply

by Tarinder Sandhu on 6 August 2012, 09:30 4.5

Tags: Corsair

Quick Link: HEXUS.net/qabkjf

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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.