vacancies advertise contact news tip The Vault
facebook rss twitter

Review: Corsair RM750

by Tarinder Sandhu on 23 September 2013, 13:00

Tags: Corsair

Quick Link: HEXUS.net/qab3bb

Add to My Vault: x

Testing results

Our testing procedures can be found at this link.

Efficiency

Load 10pc 25pc 50pc 75pc 100pc
Efficiency 84.3pc 91.7pc 92.8pc 89pc 88.4pc

Hitting 90 per cent-plus for mid-load scenarios is important for a high-quality PSU, as it enables the supply to keep temperatures in check with minimal fan airflow. As we alluded to earlier, this is why Corsair positions this as a passively-cooled supply at up to 40 per cent load, based on 25C ambient temperature.

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 +0.9pc +1.4pc +2.9pc
50 per cent +0.3pc +0.6pc +1.5pc
100 per cent -1.9pc -0.5pc +0.7pc

Most supplies overvolt with little load and undervolt when stressed. The only standout figure, which is still well within the ATX spec, is the 12V line's when it's tickled by a 10 per cent load.

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 -1.1pc +1.2pc +2.1pc
Cross-load 3.3V/5V focus -1.5pc +1.6pc +1.7pc

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, and we see lots of evidence to suggest the RM750 does a good job in those instances.

Ripple

Line/Load (mv - p-p max) 3.3V 5V 12V
10 per cent 10mV 15mV 15mV
50 per cent 25mV 15mV 25mV
100 per cent 25mV 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.

Per-line ripple is more than acceptable in all cases.

Temps

Temperatures Intake Exhaust
10 per cent 31°C 34°C
50 per cent 36°C 40°C
100 per cent 38°C 45°C

The temperatures represent a direct link to the fan speed. We determined the fan's trigger-point at around 280W of DC load, or just below the 40 per cent figure quoted by Corsair. Let's put this kind of figure into context for a moment. 280W DC can comfortably power a fully-built PC equipped with an Intel Core i7-4770K processor, 16GB memory, SSDs, and a GeForce GTX Titan graphics card.

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 0rpm None Silent
50 per cent 600rpm circa-20cfm Very quiet
100 per cent 900rpm circa-60cfm Very quiet

Corsair's built the RM750 for near-silent operation whilst also providing decent performance. Our numbers verify that it does achieve those aims.