Corsair RM750x 2021 – A Familiar Face With MegLev

Introduction

Today we’ll be covering the new RMx 2021 from Corsair, a modified version of the RMx 2018. We’ve been provided a sample to analyze. They’re offering a newer version of the same platform with higher low-load efficiency, a new MegLev fan and an updated housing. How will it hold up and is it worth considering for your upcoming system?

General Specifications

Brand Corsair
Model RM750x (2021)
Wattage 750w
Introduction year 2021
Modularity Full
Warranty 10 years

Power Specifications

3.3v 5v 12v 5vsb -12v
20a 20a 62.5a 3a 0.3a

The usual can be seen once again here. It provides full capacity on the 12v rail and uses a single rail setup.

Cables

Cable type Cable count Connector count Gauge In-cable capacitors
ATX 20+4 pin 1 1 16-20 AWG Yes
EPS12v 4+4 pin 2 1 18 AWG Yes
PCIe 6+2 pin 2 2 16-18 AWG Yes
SATA 1 4 18 AWG No
SATA 2 3 18 AWG No
4-pin peripheral 1 4 18 AWG No

Corsair gives you the cables you expect of a 750w these days. The only change I’d like to see is the same I asked for in the Aresgame AGT850 review, having another PCIe cable included to have 3 individual cables leading to the GPU. Just like the AGT, it includes dual EPS connectors, something overkill for most consumer CPUs, but still a widely requested feature.

The cables also feature in-cable capacitors. Some find these to be annoying because it makes the cables more stiff, but from the other side the capacitors do offer additional ripple filtering, which will show itself in later parts of this review.

External

Here we see the change most people will see between the 2019 and 2021 version. The outer design has been renewed to fit Corsair’s new general theme they’ve also applied to their RAM and other products. I’m personally more a fan of a simple mesh design because of it’s efficiency, but the current style gives it a very premium look.

Protections

OPP Yes (WT7502R/IN1S313i)
OCP Yes (WT7518)
OTP Yes (IN1S313i)
UVP Yes (WT7502R/IN1S313i)
OVP Yes (WT7502R/IN1S313i)
SCP Yes (WT7502R/IN1S313i)
MOV Yes

The only minor thing we lack here is having the option for setting a multirail OCP, but otherwise this is better than usually is expected with even having 12v OCP integrated.

Parts breakdown

OEM CWT
Platform Custom
Input Voltage 100-240v
Primary Converter APFC Half Bride LLC
Rectifier Synchronous Rectification
Regulator DC-DC
Fan Corsair NR140ML (12v, 0.27a)
Bearing Magnetic Levitation
Rated Lifespan 100k Hours (50c)
PCB Type Double Sided
Bulk Capacitors 2x Nippon Chemi-Con (400v, 470+390uF, 105c)
Main Switches 2x ON Semiconductor FCPF190N60E (600v, 13,1a, 100c)
APFC Controller Champion CM6500UNX + CM03X
Resonant Controller Champion CU6901VAC
12v MOSFETs 6x ON Semiconductor NTMFS5C430N (40v, 131a, 100c)
DC-DC Converters 2x UBIQ QM3054M6 (30V, 61A, 100c) + 2x QN3107M6N (30v, 70a, 100c)
DC-DC Controller UPI Semi uP3861P
Filtering Capacitors (Electronic) 14x Nippon Chemi-Con, 1x Rubycon
Filtering Capacitors (Polymer) 33x Nichicon
Supervisor IC Weltrend WT7502R + WT7518 + Infinno IN1S313i
5VSB Rectifier MakoSemi PS1045L + InPower Semiconductor ISD04N65A
Standby PWM Controller On-Bright OB5282

The RMx 2021 is very similar to it’s 2019 counterpart, the only major differences to see here being it’s fan and some minor changes to achieve higher low-load efficiency by using burst mode. As the RMx 2019 already performed very well, Corsair had little reason to make major changes to the platform, which means the dimensions and most of the parts are still the same high quality parts they’ve been providing.

Internal

Electrical Performance

Test Equipment

Electronic Loads 4x Chroma 63601-5, 2x Chroma 63600-2, 20x 63640-80-80, 2x 63610-80-20
AC Sources Chroma 6530, Keysight AC6804B
Power analyzers N4L PPA1530 x2
Sound analyzer Bruel & Kjaer 2270 G4
Microphone Bruel & Kjaer Type 4955-A
Data loggers 2x Picoscope TC-08, 2x Labjack U3-HV
Tachometer 2x UNI-T UT372
Digital multimeters Keysight U1273AX, Fluke 289, Keithley 2015 - THD
UPS CyberPower OLS3000E 3kVA x2
Transformers 3kVA x2

The equipment isn’t ours and testing done isn’t by us, but by a third party called Cybenetics and will be used in this review. You can find their efficiency standard ETA , noise standard LAMBDA , methodology , power supply database and more on their site. The results we’re showing here is based off the RM750x 2021 230v report.

Efficiency

Load DC (Watt) AC (Watt) Efficiency
Low load 1 19.989 25.023 79.883%
Low load 2 39.979 46.652 85.696%
Low load 3 60.008 68.288 87.875%
Low load 4 79.958 91.165 87.707%
Load 1 74.989 85.941 87.256%
Load 2 150.031 164.916 90.974%
Load 3 225.037 242.732 92.710%
Load 4 300.045 323.105 92.863%
Load 5 374.594 404.691 92.563%
Load 6 449.515 487.677 92.175%
Load 7 524.858 572.419 91.691%
Load 8 600.165 658.345 91.163%
Load 9 674.714 744.361 90.643%
Load 10 749.938 832.890 90.040%
Load 11 825.169 922.732 89.427%
Crossload 1 151.044 180.598 83.635%
Crossload 2 760.207 839.955 90.506%

The unit easily reaches it’s promised level of 80+ gold, and with that also meets ETA Gold without any issue, just like the older RMx models did. One of the main differences from the old RMx is also visible here, showing a higher efficiency at low loads.

Efficiency 5vsb

Load DC (Watt) AC (Watt) Efficiency
5VSB 1 0.227 0.348 65.230%
5VSB 2 0.454 0.639 71.049%
5VSB 3 2.770 3.598 76.987%
5VSB 4 5.028 6.442 78.050%
5VSB 5 7.528 9.616 78.286%
5VSB 6 14.965 19.167 78.077%

here too nothing underwhelming to be found. The unit shows efficiency well above 70% at lower loads outside of the first.

Voltage regulation – Amperage

Load 12v amperage (A) 5v amperage (A) 3.3v amperage (A) 5vsb amperage (A)
Low load 1 1.239 0.493 0.499 0.197
Low load 2 2.478 0.990 1.001 0.396
Low load 3 3.720 1.485 1.501 0.595
Low load 4 4.925 1.982 2.001 0.794
Load 1 4.426 1.981 2.003 0.994
Load 2 9.889 2.975 3.004 1.194
Load 3 15.725 3.473 3.508 1.394
Load 4 21.559 3.970 4.011 1.595
Load 5 27.020 4.965 5.017 1.795
Load 6 32.529 5.962 6.021 1.996
Load 7 38.083 6.957 7.028 2.198
Load 8 43.638 7.958 8.035 2.400
Load 9 49.570 8.459 8.525 2.400
Load 10 55.310 8.961 9.046 3.009
Load 11 61.658 8.967 9.053 3.011
Crossload 1 0.116 18.001 17.998 0.000
Crossload 2 62.516 1.000 1.002 1.000

This shows the amperages each respective load test is done at. This isn’t very interesting on it’s own, but will help understanding the table below this.

Voltage regulation – Voltages

Load 12v voltage (V) 5v voltage (V) 3.3v voltage (V) 5vsb voltage (V)
Low load 1 11.975 5.072 3.310 5.070
Low load 2 11.976 5.051 3.300 5.046
Low load 3 11.979 5.048 3.298 5.041
Low load 4 12.054 5.045 3.296 5.036
Load 1 12.056 5.046 3.296 5.032
Load 2 12.047 5.042 3.294 5.027
Load 3 12.018 5.040 3.292 5.023
Load 4 12.006 5.039 3.291 5.018
Load 5 11.994 5.037 3.290 5.015
Load 6 11.998 5.034 3.289 5.011
Load 7 11.967 5.032 3.288 5.006
Load 8 11.956 5.029 3.286 5.002
Load 9 11.947 5.025 3.284 5.000
Load 10 11.937 5.022 3.283 4.986
Load 11 11.928 5.019 3.281 4.983
Crossload 1 12.021 5.026 3.288 5.077
Crossload 2 11.947 5.026 3.283 5.012

And here is where the unit shines, showing a very tight voltage regulation on all rails, very close to nominal. Nothing to complain here.

Ripple measurements

Load 12v (mv) 5v (mv) 3.3v (mv) 5vsb (mv) Pass/Fail (ATX)
Load 1 4.90 3.50 3.30 5.30 Pass
Load 2 4.70 3.40 2.90 5.10 Pass
Load 3 8.10 3.50 3.00 4.90 Pass
Load 4 7.20 3.70 3.20 5.50 Pass
Load 5 6.60 3.70 3.00 5.70 Pass
Load 6 6.40 7.20 9.80 7.90 Pass
Load 7 6.70 3.90 3.70 5.30 Pass
Load 8 6.70 4.40 6.60 5.50 Pass
Load 9 6.20 4.90 7.10 5.50 Pass
Load 10 8.90 5.10 7.10 6.60 Pass
Load 11 9.50 5.30 9.00 6.20 Pass
Crossload 1 5.20 4.10 7.70 5.40 Pass
Crossload 2 5.30 4.50 8.00 6.30 Pass

Here is where the unit really shines. Due to the use of in-cable capacitors the cables do get a bit more stiff, but it helps filter the ripple out together with the capacitors that are already in the unit itself. Showing no higher than 9.5 mv of ripple, this is well within the margin of ATX. ATX goes by the following:

  • 12v = 120mv max
  • 5v/3.3v/5vsb = 50mv max

Fan speed + noise

Load Fan speed (RPM) Noise (dBA)
Low load 1 0 < 6
Low load 2 0 < 6
Low load 3 0 < 6
Low load 4 0 < 6
Load 1 0 < 6
Load 2 0 < 6
Load 3 0 < 6
Load 4 0 < 6
Load 5 362 7.3
Load 6 491 10.9
Load 7 712 21.0
Load 8 942 29.7
Load 9 1218 37.5
Load 10 1515 42.6
Load 11 1913 48.1
Crossload 1 591 15.2
Crossload 2 1912 48.1

This is sadly where a lot of my positive feedback about it’s performance stops for a bit. The unit isn’t extremly loud in any way, but is visibly louder at higher loads compared to it’s 2018 version. It still uses the same fan controller setup, but the fan and housing make the unit visibly louder. This is still within a more than acceptable margin, especially at lower loads. But as you push the unit, it’ll become quite a bit louder than it’s older brother.

Hold-up time

Hold-up time Power-OK time Power OK to DC loss delay
26.60 ms 23.90 ms 2.70 ms

Again, we have nothing to complain here. Corsair is well within ATX specification and the unit is well useable in combination with a UPS.

Conclusion

Overall, Corsair changed little about their RMx units with this new 2021 refresh, but that’s not a bad thing. Some of the changes like the burst mode controller make total sense, but sadly some of them are less beneficial to the unit. The new Meglev fan does improve potential lifespan of the unit, but makes the unit especially at higher loads noticably louder. Corsair is also recently going with a triangle-like pattern that visually might look nice, but makes it a bit more restrictive compared to the old housing design, and we expect this to also have a minor part in the increased noise levels compared to the 2018 version. Still, we’re overall very satisfied about it’s performance, build quality and protection set. The only thing is that Corsair has it’s competitors coming in from all sides, so it’s value over many other units can get debatable at times.

Either way, if you were planning to pick an RMx up, I can highly recommend it.

RM750x 2021

125,68
8.6

Cables

8.0/10

Internal quality

9.0/10

Protections

9.0/10

Electrical performance

10.0/10

Value

7.0/10

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