Review: Corsair HX1200i

Running the numbers

Our testing procedures can be found at this link.

Efficiency

Platinum-rated supplies should all exhibit excellent efficiencies across a wide load range. It makes sense therefore to see how the newer HXi stacks up against the Flextronics-built, all-digital AXi that's been widely available for almost three years now.

Efficiency is a tad better once we run from 25 per cent to full load. There's very little in it, however, and having 90 per cent-plus across a reasonable load is indicative of a top-quality PSU.

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.

Most supplies overvolt with little load and undervolt when stressed. The HXi isn't quite as excellent as the AXi, most likely due to the latter using digital control, but the minor variances in regulation remain very, very good.

Regulation - cross-load

How about providing uneven loads that stress particular voltage rails? In the first attempt, we've put 90A 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!

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 little variation going on here; you're looking at just under two per cent from a best-to-worst-case scenario. Again, the AXi tends to be that tiny bit better.

Ripple

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 - the raison d'etre of this supply.

Both are well inside the ATX spec, massively so in most cases, and it's only through a 'scope that you can differentiate the electrical performance of the premium Corsair duo.

Temps

Platinum-rated efficiency has the ancillary benefit of producing very little heat. Being close to 95 per cent efficient at 50 per cent means the fan doesn't have much work to do in order to keep the unit working at sensible temperatures. Both supplies are silent at 400W.

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.

Silent at low loads and remaining quiet when pushed right up to 1,200W in both cases, we believe that you will hear other parts of the system before the noise emitted by the PSU fan.