Corsair RM850x Shift PSU Review: They Shifted the Modular Panel!

The new Corsair RMx Shift series brings an innovation: a side-positioned DC connector panel. According to the brand’s claims, this provides a tremendous boost to cable management since users have an easier access to the modular panel. Moreover, all Shift models are ATX v3.o and PCIe 5.0 ready.

Corsair decided to exploit the popular RMx series, so in its new series, it uses the RMx naming scheme, but it adds a “Shift” at the end of it. This word was used because the modular panel was shifted from backward to the side. I am not sure if this change on the modular panel’s position will work on all chassis since some have special PSU compartments covering the PSU’s sides, but it is high time for the chassis manufacturers to make some changes, too.

The new Corsair RMx Shift series includes four members with capacities ranging from 750W to 1200W. In this review, I will look at the second member of the line, with 850w max power. I have already posted all their reviews for those interested in discovering more about the other Shift models, so feel free to check them out.

The MSRPs of all Corsair Shift models.

Cybenetics Report


Technical Specifications:

  • Manufacturer (OEM): CWT
  • Max Power: 850W
  • Cybenetics Efficiency: [115V] Gold (87-89%)
  • 80 Plus Efficiency: Gold
  • Noise: Cybenetics A (20-25 dB[A])
  • Compliance: ATX12V v3.0, PCIe 5.0, EPS 2.92
  • Alternative Low Power Mode support: Yes
  • Power 12V: 850W
  • Power 5V + 3.3v: 150W
  • Power 5VSB: 15W
  • Cooling: 140 mm Fluid Dynamic Bearing Fan (NR140P)
  • Semi-Passive Operation: Yes
  • Modular Design: Yes (Fully)
  • High Power Connectors: 2x EPS (2x cables), 6x PCIe 6+2 pin (3x cables), 1x PCIe 12+4 pin (600W)
  • Peripheral Connectors: 12x SATA (3x cables), 8x 4-pin Molex (single cable)
  • ATX/EPS Cable Length: 610/660mm
  • Distance between SATA connectors: 110mm
  • Distance between 4-pin Molex connectors: 100mm
  • In-cable capacitors: No
  • Dimensions (W x H x D): 150 mm x 85 mm x 160 mm
  • Weight: 1.66 kg (3.66 lb)
  • Warranty: 10 years

Box & Bundle

The box has a sticker with ATX 3.0 compatibility at its top right side. It also speaks of a 300W 12VHPWR connector.

For quite some time, Corsair has used the Cybenetics badges on its boxes. Hopefully, they will also put them at the face of the box, where they belong!

Product Photos

A sticker informs you that it is normal if the fan doesn’t spin, and you should not RMA the PSU!

The side-mounted modular panel makes this unit look weird! I have been used to rear-mounted modular panels all these years, so it is hard for me to adapt so quickly.


Modular Cables
Description Cable Count Connector Count (Total) Gauge In Cable Capacitors
ATX connector 20+4 pin (610mm) 1 1 16-18AWG No
4+4 pin EPS12V (660mm) 2 2 18AWG No
12+4 pin PCIe (660mm) 1 1 16AWG No
6+2 pin PCIe (660mm+100mm) 3 6 16-18AWG No
SATA (460mm+110mm+110mm+110mm) 3 12 18AWG No
4-pin Molex (450mm+100mm+100mm+100mm) 2 8 18AWG No
AC Power Cord (1370mm) – C13 coupler 1 1 18AWG

There are no in-cable caps, and the provided cables and connectors are sufficient to deliver the PSU’s full power effortlessly. I would like to see a longer distance between the peripheral connectors.

Protection Features

OCP (Cold @ 28°C)

12V: 87.6A (123.73%), 12V
5V: 29.2A (146%), 5.039V
3.3V: 29.1A (145.5%), 3.297V
5VSB: 4.8A (160%), 4.936V

OCP (Hot @ 41°C)

12V: 88A (124.29%), 12.021V
5V: 29.3A (146.5%), 5.048V
3.3V: 29.1A (145.5%), 3.297V
5VSB: 4.8A (160%), 4.931V

OPP (Cold @ 29°C)

1051.39W (123.75%)

OPP (Hot @ 40°C)

1058.13W (124.54%)


✓ (141°C @ 12V Heat Sink)


12V to Earth: ✓
5V to Earth: ✓
3.3V to Earth: ✓
5VSB to Earth: ✓
-12V to Earth: ✓


Proper operation



Surge: MOV
Inrush: NTC Thermistor & Bypass relay

OCP at 12V and OPP are correctly set. On the other hand, OCP on the minor rails is set a bit high, especially at 3.3V. But there are no load regulation or ripple issues. All other protection features are present too, and working well.

Part Analysis

General Data
Manufacturer (OEM) CWT
PCB Type Double Sided
Primary Side
Transient Filter 6x Y caps, 2x X caps, 2x CM chokes, 1x MOV
Inrush Protection 1x NTC Thermistor SCK207R0 (7 Ohm) & Relay
Bridge Rectifier(s)
2x  GBJ1506 (600V, 15A @ 100°C)
2x Infineon IPA60R125P6 (600V, 19A @ 100°C, Rds(on): 0.125Ohm) &
1x Sync Power SPN5003 FET (for reduced no-load consumption)
APFC Boost Diode
1x On Semiconductor FFSP0865A (650V, 8A @ 155°C)
Bulk Cap(s)
2x Nippon Chemi-Con (400V, 470uF each or 940uF combined, 2,000h @ 105°C, KMW)
Main Switchers
2x STMicroelectronics STF33N60M2 (600V, 16A @ 100°C, Rds(on): 0.125Ohm)
Driver IC(s)
Champion CM6500UNX
Digital Controllers Champion CU6901VAC
Primary side: APFC, Half-bridge & LLC converter
Secondary side: Synchronous Rectification & DC-DC converters
Secondary Side
+12V MOSFETs 6x On Semiconductor NTMFS5C430N (40V, 131A @ 100°C, Rds(on): 1.7mOhm)
5V & 3.3V DC-DC Converters: 4x UBIQ QN3107M6N (30V, 70A @ 100°C, Rds(on): 2.6mOhm)
PWM Controllers: UPI-Semi uP3861P
Filtering Capacitors Electrolytic: 4x Nichicon (2–5,000h @ 105°C, HD), 1x Nichicon (5-6,000h @ 105°C, HV), 1x Nippon Chemi-Con (1-5,000h @ 105°C, KZE), 1x Nippon Chemi-Con (4-10,000h @ 105°C, KYA), 4x Nichicon (4-10,000h @ 105°C, HE)
Polymer: 22x FPCAP, 5x Nippon Chemi-Con
Supervisor IC Weltrend WT7502R
Fan controller Microchip PIC16F1503
Fan Model Corsair NR140P (140mm, 12V, 0.22A, Fluid Dynamic Bearing Fan)
5VSB Circuit
1x PS1045L SBR (45V, 10A)
Standby PWM Controller On-Bright OB2365T

Channel Well Technology (CWT) is the OEM of all RMx Shift models. The same manufacturer builds the RMx units. The RMx Shift models have a completely different layout from the RMx, because of the PCB changes that the side-mounted modular panel required. Aside from that, most of the parts that Corsair used are the same as the RMx, including the PFC and LLC resonant controllers, the 5VSB circuit, the housekeeping IC and the PWM controllers of the DC-DC converters. The 750W and 850W use smaller PCBs than the 1000W and 1200W units, but the layout is the same. The build quality is high, and Corsair used top-notch parts to achieve high performance and increased reliability. The main differences between the 750W and 850W models with the 1000W and 1200W ones are the topology on the primary side. The former use a half-bridge topology, while the latter utilize a full-bridge one, allowing for higher power output while keeping energy losses in control. All models feature an LLC resonant converter for increased efficiency.

The APFC and resonant controllers, the DC-DC converters that generate the minor rails, the 5VSB circuit, the supervisor IC, the fan controller, and the fan are the same in all Shift models. The key differences are in the bridge rectifiers, the FETs, the NTC thermistors, the bulk caps, the filtering caps on the secondary side, and the cooling fan. Corsair decided to ditch the ML fan of the RMx unit in favor of the NR140P FDB fan, which Hong Hua provides.

Load Regulation

Ripple Suppression

Test 12V 5V 3.3V 5VSB Pass/Fail
10% Load 6.4 mV 3.5 mV 4.9 mV 7.1 mV Pass
20% Load 15.9 mV 3.9 mV 5.4 mV 8.3 mV Pass
30% Load 10.5 mV 5.6 mV 6.8 mV 9.8 mV Pass
40% Load 11.1 mV 8.0 mV 10.2 mV 12.0 mV Pass
50% Load 13.0 mV 5.8 mV 8.1 mV 13.0 mV Pass
60% Load 14.1 mV 8.0 mV 10.8 mV 14.8 mV Pass
70% Load 16.5 mV 7.4 mV 10.3 mV 17.4 mV Pass
80% Load 18.4 mV 11.7 mV 18.5 mV 19.1 mV Pass
90% Load 20.1 mV 12.3 mV 19.8 mV 20.1 mV Pass
100% Load 25.3 mV 10.5 mV 17.0 mV 26.3 mV Pass
110% Load 27.1 mV 11.2 mV 18.3 mV 27.7 mV Pass
Crossload 1 19.2 mV 5.5 mV 12.9 mV 13.1 mV Pass
Crossload 2 6.4 mV 4.7 mV 5.3 mV 10.7 mV Pass
Crossload 3 5.7 mV 3.4 mV 11.9 mV 9.6 mV Pass
Crossload 4 25.1 mV 9.9 mV 13.5 mV 24.4 mV Pass

Transient Response

20% Load – 20ms

Voltage Before After Change Pass/Fail
12V 12.080V 11.850V 1.90% Pass
5V 5.033V 4.930V 2.04% Pass
3.3V 3.300V 3.203V 2.93% Pass
5VSB 5.019V 4.976V 0.86% Pass

50% Load -20ms

Voltage Before After Change Pass/Fail
12V 12.048V 11.942V 0.87% Pass
5V 5.021V 4.931V 1.79% Pass
3.3V 3.294V 3.191V 3.11% Pass
5VSB 4.981V 4.939V 0.84% Pass

I want to see close to 1% deviations at 12V, but this is not the case here.

Transient Response ATX v3.0 & 12VHPWR Connector Tests

The PSU passed all ATX v3.0 transient response tests with success.

Hold Up Time

The hold-up time is longer than required.


The PSU supports Alternative Low Power Modes.

Inrush Current

Efficiency Normal, Light & Super-Light Loads

The platform is highly efficient at light loads.

Average Efficiency 5VSB

The 5VSB circuit needs improvement to become more efficient.

Vampire Power

Average Efficiency

The average efficiency is high enough but doesn’t destroy the competition.

Average PF

Average Noise

The average noise output is low. Only a be quiet! and an Asus unit outperform the Shift model in this section.

Fan Noise & Speed Maps @ 28-32 °C

The 30 dBA mark is passed with higher than 700W loads. The PSU’s operation is dead silent with minimal and up to 600W loads.

Overall Performance

Overall performance is satisfactory, but it needs more boosting if Corsair wants to get it closer to the rest competitors in this category.


The RM850 Shift, similar to its 750W sibling, loses some performance compared to the RM850x (2021), but it is notably quieter, thanks to the FDB fan that Corsair used instead of the ML fan of the unit above. It might not meet RM850x eye-to-eye, but its overall performance is still competitive and close to the top of this category.

Load regulation is within 1% on all significant rails, ripple suppression is good, although not top-notch as in the RM850x, and the hold-up time is longer than 20ms. I still want a better transient response at 12V and 5V in non-ATX v3.0 scenarios. Efficiency could also take a slight boost to meet the rest of Gold competitors at normal and high loads. The platform is highly efficient at light and super-light loads but doesn’t perform similarly at higher loads. Lastly, lower inrush currents with 230V input would be highly welcome, too.

The major selling points of all RMx Shift units are the side-mounted modular panels, the ATX v3.0 and PCIe 5.0 compatibility, and low noise output. These units also feature a high build quality, ensuring they will outlive the extended, ten-year warranty. Kudos to Corsair for thinking outside of the box and offering a PSU with a unique design. Hopefully, chassis manufacturers will welcome this new PSU design and make their products compatible.




  • Full power at 47°C
  • ATX v3.0 and PCie 5.0 ready
  • Unique design (side-mounted modular panel)
  • Cybenetics ratings besides 80 PLUS (means extra super-tough testing)
  • Top build quality
  • High performance
  • Properly set OCP at 12V and OPP
  • Silent operation
  • Good enough ripple suppression
  • Highly efficient at light loads
  • Long hold-up time
  • Low inrush current with 115V
  • ALPM support
  • Lots of connectors, including a 600W 12VHPWR
  • Fully modular
  • Low vampire power
  • Quality, FDB fan
  • 10-year warranty


  • The transient response should be better at 12V
  • The 5VSB rail could be more efficient
  • The short distance between all peripheral connectors

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3 thoughts on “Corsair RM850x Shift PSU Review: They Shifted the Modular Panel!

  1. my unit’s PCIe 12+4 pin cable is only 12+2 pin and the box says <=300w pcie 5.0 the same as your box your cable's picture is too blur

    can this cable do 600w?for example 4090 oc? In the future I may change my computer to a 600w gpu and a 50w cpu
    currently I am not using this cable. I don't have a new gpu .currently running a 350w 3080ti

    I am Chinese.We may get different versions.
    I get this psu from RMA my rm850i.So very happy

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