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Corsair RM750x PSU Review

Corsair released its RMx PSU line, which the company claims will offer good performance along with silent operation. Unlike the RMi models, the RMx units lack a digital interface, a fan test button, and uses a Rifle bearing fan instead of an FDB version.

Load Regulation, Hold-Up Time And Inrush Current

To learn more about our PSU tests and methodology, please check out How We Test Power Supply Units. 

Primary Rails And 5VSB Load Regulation

Load Regulation testing is detailed here.

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Hold-Up Time

Our hold-up time tests are described in detail here.

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The registered hold-up time was very high. A small difference gave the Corsair RM750i the lead here, however.

Inrush Current

For details on our inrush current testing, please click here.

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Our power analyzer showed a quite high inrush current reading of 230V. This shouldn't trouble you, however, since inrush current stayed below 50A in any case.

Load Regulation And Efficiency Measurements

The first set of tests reveals the stability of the voltage rails and the PSU's efficiency. The applied load equals (approximately) 10 to 110 percent of the maximum load the supply can handle, in increments of 10 percentage points.

We conducted two additional tests. During the first, we stressed the two minor rails (5V and 3.3V) with a high load, while the load at +12V was only 0.10A. This test reveals whether a PSU is Haswell-ready or not. In the second test, we determined the maximum load the +12V rail could handle with minimal load on the minor rails. 
 

Test12V5V3.3V5VSBPower(DC/AC)EfficiencyFan SpeedFan NoiseTemp(In/Out)PF/AC Volts
104.403A1.985A1.988A0.995A74.74W85.47%0 RPM0 dBA49.36°C0.967
12.070V5.042V3.318V5.018V87.45W42.08°C115.1V
209.863A2.970A2.984A1.195A149.70W89.33%0 RPM0 dBA51.19°C0.988
12.049V5.042V3.315V5.015V167.59W43.03°C115.1V
3015.690A3.475A3.499A1.395A224.85W90.45%0 RPM0 dBA51.94°C0.993
12.030V5.042V3.313V5.009V248.58W43.17°C115.1V
4021.530A3.963A3.984A1.595A299.70W90.63%0 RPM0 dBA54.64°C0.995
12.009V5.040V3.311V5.004V330.70W43.80°C115.1V
5027.043A4.963A4.983A1.797A374.71W90.36%0 RPM0 dBA58.11°C0.997
11.989V5.041V3.308V5.002V414.71W45.61°C115.1V
6032.575A5.951A5.990A2.000A449.63W89.83%615 RPM25.2 dBA45.38°C0.997
11.968V5.039V3.305V4.996V500.53W64.21°C115.1V
7038.130A6.947A6.997A2.199A524.57W89.24%680 RPM27.1 dBA45.93°C0.997
11.946V5.038V3.300V4.993V587.83W66.01°C115.1V
8043.712A7.940A8.005A2.404A599.59W88.57%820 RPM30.9 dBA47.67°C0.997
11.924V5.036V3.297V4.988V676.95W68.02°C115.1V
9049.751A8.445A8.524A2.402A674.63W87.86%915 RPM34.9 dBA47.90°C0.998
11.900V5.035V3.296V4.988V767.82W68.70°C115.1V
1055.549A8.941A9.012A3.015A749.39W87.03%1075 RPM38.0 dBA48.71°C0.998
11.876V5.034V3.295V4.970V861.09W70.78°C115.1V
1161.992A8.946A9.017A3.015A824.36W86.11%1190 RPM40.5 dBA49.48°C0.998
11.851V5.031V3.294V4.969V957.30W72.38°C115.1V
CL10.098A18.024A18.003A0.004A152.42W82.11%765 RPM29.4 dBA46.16°C0.990
12.039V5.074V3.320V5.116V185.62W60.06°C115.1V
CL262.453A1.002A1.003A1.002A754.98W87.59%1090 RPM38.2 dBA47.43°C0.998
11.875V5.022V3.301V4.999V861.99W67.99°C115.1V

At +12V load regulation was decent; however, it didn't manage to meet the competition. We probably pushed the PSU too hard, since at full load the ambient inside the hot box reached 49 C, while we usually stay below 46 C. We wanted to see how loud the unit's fan could be under extremely tough conditions, however, and also verify Corsair's claim about the 50 C rating of this unit. Judging from our overload test, which was conducted at a temperature close to 50 C, the RM750x proved that it has no problem at all operating under extremely tough conditions, delivering its full load for prolonged periods. In addition, thanks to the silent fan and the optimized fan profile, the noise output of this PSU is at very low levels. On top of that, the PSU didn't engage its fan with up to 50 percent load and with an ambient of almost 46 C.

The minor rails, especially the 5V one, managed to keep their deviations low by utilizing the extra voltage sense wires of the Type 4 cables that equip the PSU. And it seems that the increased operating temperatures didn't affect the performance of the DC-DC converters. Finally, the PSU cleared all requirements of the 80 Plus Gold certification. With 100 percent load, it was a close shot, however. As we have mentioned so many times in past reviews, the 80 Plus organization conducts all testing at only 23 C, while we conduct our tests at much higher temperatures, seeking to push the PSUs to their limits. If you want to check performance at lower ambient temperatures (around 28 C), you can take a look at our Cross-load tests on page six, during which we dial (automatically) thousands of possible load combinations.

Aris Mpitziopoulos is a Contributing Editor at Tom's Hardware US, covering PSUs.