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Corsair RM750i Power Supply Review

Corsair is revamping its RM line, adding the letter "i" to highlight a more advanced digital interface — today we check out the RM750i.

Our Verdict

The Corsair RM750i is a great PSU offering high performance, along with silent operation under all conditions. Currently, the RM750i is among the best PSUs money can buy in this category, bringing Corsair up to speed with the tough competition.

For

  • Full power at 47.5 °C • Efficient • Load regulation • Ripple suppression • Silent operation • Hold-up time • FDB fan • Quality caps • Fully modular • Digital interface • Fan-test button • Multi or single +12V rail • Warranty

Against

  • Single EPS connector • Distance between four-pin Molex connectors

Introduction

Corsair has revamped its RM line, adding the letter "i" to it, which highlights the use of a more advanced digital interface compared with the previous generation. Today we will test how the RM750i 750 Watt power supply fares against the competition.

Corsair's RM line includes the most silent PSUs money can buy today and features a digital interface, which gathers limited information regarding the PSU's status and operation. Since digital circuits are better than analog ones, Corsair decided that it was time to introduce its new RMi line, which includes four models with 650 W, 750 W, 850 W and 1 kW capacities. The major differences between the RM and the new RMi series are:

  • Seven-year warranty instead of five.
  • Exclusive use of Japanese capacitors.
  • Fluid Dynamic Bearing (FDB) fan instead of the Riffle-bearing fan that the RM units have.
  • A more advanced digital circuit that allows the monitoring of power in/out, efficiency, output voltages and temperature, as well as DC load and fan speed.
  • The new digital circuit provides the ability to create a custom fan profile and convert the PSU's +12V rail from a single one to multiple +12V rails.

All of the above new features look very interesting, and we have high expectations for the new RMi units, especially since they are built by Channel Well Technology, an OEM that Corsair has enjoyed a long and satisfying relationship with. The PSU undergoing tests today will be the RM750i unit, which, thanks to its mid-level capacity, addresses a significant portion of users. With four PCIe connectors, the RM750i can support up to two VGAs with double PCIe sockets each, and Corsair promises a very silent operation under all conditions, which will make users happy, especially those who dislike noisy system components. What we don't want to see is a very high temperature threshold for the fan's activation, which was the case in previous RM units. However, the new RMi PSUs allow users to create custom fan profiles that better suit their needs and systems.

Specifications

Corsair deliberately kept the same efficiency rating as the previous RM line. Increasing it from Gold to Platinum would have made the new RMi units compete directly with the HXi line, Corsair's higher-end PSUs. This is something that PSU companies try to avoid, especially ones with large product portfolios like Corsair. A crucial update to the new units was the 10 degree Celsius increase in the maximum operating temperature at which full power can be delivered continuously. This means that the platform has been upgraded to withstand increased heat and that it is more reliable compared with the older one. This is also reflected in the addition of two years to the warranty period, to seven years.

The RM750i PSU comes with all available protection features, is fully modular and uses the same FDB fan as the other high-end Corsair units. Thanks to its quality bearing, the NR135P fan will last for a long time; on top of that, it is very silent, even at higher speeds. Moreover, it is supported by a highly relaxed fan profile and a semi-passive mode operation.

Power Specifications

Rail3.3V5V12V112V212V312V412V55VSB-12V
Max. PowerAmps2525404040404030.8
Watts150750159.6
Total Max. Power (W)750

The RM750i PSU comes with multiple +12V rails with the OCP set at 40 A for each one of them, in order to avoid problems with energy-hungry VGAs. The minor rails are very powerful for a contemporary PSU, while the 5VSB rail is a little stronger than the average.

Rail3.3V5V12V5VSB-12V
Max. PowerAmps252562.530.8
Watts150750159.6
Total Max. Power (W)750

Up to 62.5 A can be delivered in the single +12V rail mode, thus the PSU's total capacity can be handled by the +12V rail alone. This is a feature typically seen in modern PSUs that use DC-DC converters for the generation of the minor rails.

Cables And Connectors

Modular Cables
DescriptionCable CountConnector Count (Total)
ATX connector 20+4 pin (610mm)11
4+4 pin EPS12V (660mm)11
6+2 pin PCIe (610mm)24
SATA (400mm+100mm+100mm+100mm)14
SATA (550mm+100mm+100mm+100mm)14
Four-pin Molex (450mm+100mm+100mm)13
Four-pin Molex (450mm+100mm+100mm+100mm)14
FDD Adapter (+100mm)22
C-Link USB Cable (800mm)11
C-Link I2C Cable (800mm)11

For a 750 W PSU, the number of cables provided is sufficient for the majority of users; however, we would have liked to have seen an extra EPS cable. Normally, a PSU of this category comes with two EPS cables, or at least a single EPS and one ATX12V (4-pin) cable, in order to support high-end mainboards. The number of SATA and peripheral Molex connectors is adequate. The cable bundle also includes two Corsair Link cables, with one of them hosting a mini USB connector. Finally, the PCIe cables consist of thicker 16AWG wires, while the rest of the connectors use the standard 18AWG gauges.

Power Distribution

According to Corsair, when the PSU operates in multi +12V mode -- which is selected by default -- the Over Current Protection (OCP) is set to 40 A on each of the 8-pin modular connectors (for PCIe and EPS cables). The same OCP trigger point also applies to the 24-pin ATX connectors, and all 6-pin modular connectors are fed by a virtual +12V rail with 40 A OCP as well. What this means is that power distribution is optimal since all PCIe and EPS cables are fed by dedicated +12V rails and the same applies to the 24-pin ATX connector.

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Power Supplies in the Forums

  • JQB45
    Nice to see quality improving some.
    Reply
  • Luay
    Aris

    Thanks for the thorough review.

    The RM750i does beat the G2 750 at $10 more, which is a good trade for a mpore quite operation, and is $20 cheaper than the Snow Silent 750, but how does it compare to the $10 more expensive P2 750?
    Reply
  • Aris_Mp
    I am sorry but I haven't reviewed the P2 750 model yet. However since it is Platinum it should be compared with the HX750i.
    Reply
  • jonnyguru
    Unless efficiency isn't that important to you.
    Reply
  • Luay
    No I'm comparing it based on price.

    Since the gold rated RM750i and the platinum P2 750 are $10 apart, excluding the rebate, and as Jonny (The Jonny??) said, a few %s of efficiency isn't as important to me as something as tangible as emitting noise.
    Reply
  • Dan414
    This seems like the droids/PSU I've been looking for. That or maybe the 850i. Also, I like the white lettering - that way it will match my case no matter what lighting I have inside.
    Reply
  • synphul
    I'm confused, there's no other product that compares to the corsair rm750i except the evga g2 750 and the seasonic snow silent 750 which is a higher category and price. Yet isn't that the ss-750km3 sitting at $10 cheaper?

    Cwt may be improving but it's not ss quality. Hard to face the two off when they're so close in price or the seasonic is cheaper. I fail to see how it's a better option than the competition. A better option than their own lineup maybe, but that's not saying a ton.

    I suppose it's true it comes with corsair link, though with psu's already this quiet not sure the need is there to control the fan beyond active variable control built in and silent mode at low draw. I've never needed to monitor my psu temp or control the fan speed even on a plain old active fan design. Comes off as a bit gimmicky to try and create added value. Don't get me wrong, this would be nice on an otherwise loud psu with no fan control and no silent operation mode at all but in the face of being quiet and having variable/silent fan operation it's a little redundant.

    Idk, like I said it's nice to see they're trying to improve quality in some areas but they don't even come in under the competition. As of right now they're more expensive than the competition. Personally I'll stick with seasonic.
    Reply
  • trifler
    If any PSU companies read this, I want to see molex discontinued, at least on the non-modular power supplies. At least offer some power supplies that don't have molex.
    Reply
  • fil1p
    It's good to see that all the caps a Japanese on this one. I like Corsair PSUs, but the last gen RM series had some lower quality caps in there, which quite frankly shouldn't have been in an enthusiast PSU at that price point in the first place.
    Reply
  • jonnyguru
    16336613 said:
    Cwt may be improving but it's not ss quality.

    How do you know? ;-)

    16336613 said:
    I suppose it's true it comes with corsair link, though with psu's already this quiet not sure the need is there to control the fan beyond active variable control built in and silent mode at low draw. I've never needed to monitor my psu temp or control the fan speed even on a plain old active fan design.

    You can also monitor voltages and load and calculate efficiency. So it does a lot more than what you're stating.
    Reply