Corsair RMx Series 650 & 850 Power Supply Reviews

Manufacturer: Corsair Corsair RMx Series 650 & 850 Power Supply Reviews

Corsair is updating their RMx Power Supply line and we take a look at two of their mid to upper level ATX sized models here, the 650 watt and 850 watt variants. These units are designed to deliver efficient system power, have modular cabling and an overall 80 PLUS Gold efficiency rating. Additionally, these newer RMx units feature a quiet magnetic levitation fan specifically tuned for quiet airflow within a PSU. This new RMx series also uses only 100% Japanese capacitors rated for up to 105°C, which is recognized to deliver improved electrical performance.

Corsair has configured the cooling to be near silent at low electrical loads and has built in support for Microsofts Modern Standby sleep mode, which allows for very fast wake-from-sleep. In practice, I have to say this actually seemed to make a slight difference in that wake up time was PDQ (that’s Pretty Darn Quick).

While I am not at the level of our retired former PSU evaluator, Lee Garbutt, I am certainly up for checking them out and pushing them hard with some overclocking.

Product Specifications

Corsair RMx Series 650 & 850 Power Supply Reviews - Cases and Cooling 25

Cable Configurations Included per wattage level:
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Protection Mechanisms
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All Prices are Corsair MSRP

  • 550W: $119.99
  • 650W: $129.99
  • 750W: $139.99
  • 850W: $149.99
  • 1000W: $189.99
Manufacturer Description
“CORSAIR RMx Series fully modular power supplies deliver clean, reliable 80 PLUS Gold efficient power to your system. Since RMx Series power supplies are synonymous with quality and performance, the inclusion of an award-winning CORSAIR ML fan is a natural choice. This particular ML fan, however, has undergone rigorous and extensive testing to tune it specifically for PSUs.”

Key Corsair Features

  • Magnetic Levitation Fan: Utilizes magnetic levitation bearings and custom engineered rotors for high performance and low noise.
    • According to Corsair, this particular ML has undergone rigorous and extensive testing to tune it specifically for PSUs
    • In my actual use, the fan seemed virtually noiseless, and I certainly could not pick it out amongst all the other fan and system noises.
  • 100% All Japanese 105°C Capacitors: Premium internal components ensure unwavering power delivery and long-term reliability.
  • Modern Standby Compatible: Extremely fast wake-from-sleep times and better low-load efficiency.
  • Zero RPM Fan Mode: At low and medium loads the cooling fan switches off entirely for near-silent operation.
  • Fully Modular: Only connect the cables your system needs, making clean and tidy builds easier.
  • Compact Size: A 160mm-long casing ensures an easy fit in almost all modern enthusiast PC cases. (The RMx 1000 is 180mm long)
  • 80 PLUS Gold Certified: High efficiency operation for lower power consumption, less noise, and cooler temperatures.
  • Ten-Year Warranty: Your guarantee of reliable operation that will last across several system builds.

Packaging and Parts

You can’t miss them on the shelf, the Corsair packaging is bright freaking yellow – but that’s probably the point. On the inside, the units are nicely suspended in stiff foam surrounds, I suppose to more easily survive world-wide delivery agents. One nice helpful detail seen from the outside of the packaging is the pictured list and visual guide for the included cabling, detailing where that cable goes and how many are included. See those pics below. The included cabling is grouped together in a heavy clear plastic bag, which if you’re careful while opening them up can be reused. It’s serviceable but not quite as nice as the cloth-like cable bags packaged with many PSUs. Use and warning manual and a decent supply of small zip ties round out the included parts.

Your PSU would also be equipped with a proper regional wall power plug, as these units are suitable to run on AC input from 100v – 240v. Also note that all these new Corsair RMx units are the same size, except for the 1000w which is 20mm longer.

What’s Inside?

See that final tag reminder in the picture below? Let me rephrase: Your PSU is not broken, the ML fan just does not spin until it gets hot or current draw gets high enough. Do not call for an RMA, thank you.

The other, much smaller anti-tamper sticker over a screw was a big help to me because it let me know which screws to remove to get the case open. Obligatory warning: do not do this yourself. My father was an IBM field engineer and I own a digital multimeter and know how to use it – mostly.

Corsair RMx Series 650 & 850 Power Supply Reviews - Cases and Cooling 39
Corsair RMx Series 650 & 850 Power Supply Reviews - Cases and Cooling 40
Corsair RMx Series 650 & 850 Power Supply Reviews - Cases and Cooling 41

The most readily apparent thing to me after taking a look inside was that the basic layout for this new RMx line was the same. Meaning that the units up to 1000w all seemed to use the same board, with varying component count or capacity. This seems to speak well towards the robustness of the design, that is suitable for various power levels. The differences between the RM650x and RM850x are visually apparent in the size of the bulk stage capacitors, the size of the driver and main transformers, and how many output capacitors exist (which is partially determined by how many wiring harness ports exist, the RM850x just has more of them).

RM650x, then RM850x in the image pairs below.

One more parting shot of the magnetic levitation bearing fan. I have to say, this was an extremely quiet fan, and did not even spin at low loads. Final note on the internals, the clear plastic side guards are a nice touch to keep metal side panels away from conductive surfaces, as well as prying fingers.

RMx ML Fan

Testing Setup

Our test bench today was provided by Thermaltake, with the Core P3 open-air chassis – making these kinds of component reviews much easier – so a big thank you to them first of all.

The test system is a solid mid-upper range configuration, to give the Corsair RMx units a bit of a challenge.

  • Intel Core i7-10700k
  • Gigabyte Z490 Aorus Master motherboard
  • 32GB of 3200 RAM from Corsair
  • be quiet! 280mm AIO CPU cooler with Corsair 140mm RGB fans
  • Samsung 960 1TB SSD and Micron 1TB SSD
  • Pair of new Thermaltake 120mm TOUGHFANS to simulate additional chassis fans (they’re the dapper looking grey fans on the desk, will be taking a closer look at these soon)
  • 10Gbe PCIe Aquantia networking card
  • A Passmark PSU inline testing device

A secondary laptop was configured to collect data over USB from the Passmark device, and to give expanded and near instantaneous feedback for power throughput, current, voltages and timings. The previous generation RM1000x was left physically attached to the Thermaltake Core P3, but electrically disconnected.

A simple software scheme was configured to push the system to consume a significant amount of power by simultaneously running AIDA64 stress testing and the DX11 GPU stress Unigine Heaven at 1080p Ultra, windowed.

Notice I did not mention a GPU? More on that below.

Corsair RMx Series 650 & 850 Power Supply Reviews - Cases and Cooling 42
Corsair RMx Series 650 & 850 Power Supply Reviews - Cases and Cooling 43
Corsair RMx Series 650 & 850 Power Supply Reviews - Cases and Cooling 44

In the above left side picture, you can see the Corsair “no-fan-spin” in action, where the draw from the system is around 175 watts total, and the RM650x has not yet turned on the fan. According to the specifications, the fan should start to run at about 400RPMs with around 195w loading at 4.7dBa of noise. The picture on the right is a visual rendition of computer mad scientist day in action.

Swapping GPUs to test loading

Beyond just running the CPU with and without an overclock, my plan was to swap around different GPUs to create different power requirements. I started with the iGPU, then moved to an EVGA GTX1070, then a EVGA 2080 triple slot, and finally to an AMD Vega Frontier with 16GB of HBM vram to power.

Corsair RMx Series 650 & 850 Power Supply Reviews - Cases and Cooling 45

What did I Learn?

We are not going to be running a set of graphs here, because I was unable to consistently capture a repeatable power loading and sequence of events scenario for comparison purposes. I will try and get that process down in the future. I did warn you that I was no Lee Garbutt.

I did note that actual total system usage was a lot lower then I imagined, even with heavy processing.


Without a GPU, the system was only drawing about 200 watts. Adding our 1070 to the mix, brought the peak up to about 340 watts under load. Again, this is a full press AIDA64 and DX11 Unigine Heaven 1080p Ultra at the same time.


Swapping in the triple slot RTX 2080 brought peak wattage of the test system to around 435. No OC applied yet, and this is still being handled nicely by the RM650x. I might have suggested a higher wattage PSU for such a configuration. However, with overclocking applied, the power requirements should shoot up dramatically and fast.

RX Vega Frontier

Using the Radeon RX Vega Frontier did not disappoint however. Peak power usage shot up to into the 550 watt range, and this eventually proved too much for the RM650x to handle. Because when your trying to generate a situation having high power draw, bring a fully volt’d Vega GPU to the fight.

Corsair RMx Series 650 & 850 Power Supply Reviews - Cases and Cooling 46
Corsair RMx Series 650 & 850 Power Supply Reviews - Cases and Cooling 47

In the real world

The situation I created tells us a couple things, right here in the real world. After OC’ing the 10700k to all core 4.9Ghz, and forcing the Frontier to utilize AMD’s game drivers then applying “quick” memory and GPU overclocking, the total system power of around 550 watts still seemed like something you might think the RM650x might have handled. But it could not. The motherboard reset, sending out that classic symptom that with just a little more voltage, or a bit more aggressive current flow to the CPU, this OC could be stabilized (I had already done both). I know I could have also undervolted the GPU, and that probably would have solved the reset under load problem, but I was trying to see how hard I could really push the PSUs here.

Swap to the RM850x

So instead, I just left all the settings as they were, with the system failing under heavy load and just swapped over to the RM850x. That worked like a charm, with the system now running benchmarks without crashing out. It might be obvious, but it’s nice to verify that even if your total system draw “fits” within your PSU rating, it still might be beneficial to stabilize your overclock to go up a level or two for your power supply. I have to hand to the Corsair RM650x though, as it was operating near the upper end of range and definitely outside its sweet spot efficiency area.

Be Most Efficient

Power supplies operate within their efficiency curve, where they can most easily supply at around 50% of their rated capacity. Plus not all voltage rails are treated equally, and while I did track individual rails, the one number of say 550 watts, does not indicate if a single 12v rail was over rating while others remained within capacity.

Corsair RMx Series 650 & 850 Power Supply Reviews - Cases and Cooling 48


For those that want to jump to the end of the story, here you are.

Corsair has a reputation in usually making quality power supplies, and nothing in my experience so far with the RM650x and RM850x leads me to believe that these are anything but. It’s rather difficult to fully measure the capabilities of PSUs without a lab full of expensive test equipment, so I can only relay my experience and inline load readings with them so far.

In all my testing, indicated voltages stayed within acceptable values, current supply was within spec and initial timings were correct and the only “faults” I could reliable generate were when pushing them outside their efficiency zone with “reckless” overclocking. Even then, my perception is they performed well, even outside their expected rating (especially given that a common rule of thumb for an approximate 50% efficient delivery rate, is to have almost twice the power capacity on tap).

As an OC enthusiast you already know you will likely need a higher end PSU for your rig, and I want to affirm your choice that getting an 850 or 1000w will not be overkill.

If your building a mid level gaming PC, I would steer you towards a 650-750w range with the expectation that you should keep your OC mild for best stability.

Corsair’s refreshed RMx line has a PSU suitable for pretty much all PC build levels. Their 80 Plus GOLD rating, silent operation at lower loads, coupled with an outstanding 10 year warranty makes it easy to suggest that you should check them out. Pricing might seems a bit high, as there are budget conscience alternatives available, but perhaps not at this level of quality or expected longevity.

In reviewing the RM650x and RM850x, I could find no build quality issues or real operational faults – unless you count my unreasonable attempt to get a 650 watt unit to deliver 800+ watts? No, that one is on me.

pcper gold award

Review Disclosures

This is what we consider the responsible disclosure of our review policies and procedures.

How Product Was Obtained

The product is on loan from Corsair for the purpose of this review.

What Happens To Product After Review

The product remains the property of Corsair but is on extended loan for future testing and product comparisons.

Company Involvement

Corsair had no control over the exact content of this review but was consulted prior to publication on best practices regarding certain testing procedures.

PC Perspective Compensation

Neither PC Perspective nor any of its staff were paid or compensated in any way by Corsair for this review.

Advertising Disclosure

Corsair has purchased advertising at PC Perspective during the past twelve months.

Affiliate Links

This article could contain affiliate links to online retailers. PC Perspective may receive compensation for purchases through those links.

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About The Author

Brett VanSprewenburg

Years of geek-ism in programming, digital image processing, capture, compression and other online application work has landed Brett here - amongst his many endeavors - webmaster and contributor @ PC Perspective. Whether its wrenching on race cars, dune buggies or web sites, only the size and shape of the tools are different. The solution always starts in your head.

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