Power supplies / Compare

CORSAIR RM850x (2024) vs Montech Century II 1200W

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Product A: CORSAIR

RM850x (2024)

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B

Product B: Montech

Century II 1200W

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Only differences

ACORSAIR RM850x (2024)

BMontech Century II 1200W

General

5 of 12 differ

Series

RMx1Maker product pagecorsair.com/us/en/p/psu/cp-9020270-na/rmx-series-rm850x-fully-modular-power-supply-cp-9020270-naRead 14 October 2026

Century II1Maker product pagemontechpc.com/century-ii-1200wRead 14 October 2026Page title: CENTURY II 1200W in the CENTURY line of 80 PLUS Gold units.

Model numbersiMaker identifiers for this exact model and its listed variants. Excludes sibling models and other generations.

CP-9020270-NA, CP-9020270-EU, CP-9020270-UK1Maker product pagecorsair.com/us/en/p/psu/cp-9020270-na/rmx-series-rm850x-fully-modular-power-supply-cp-9020270-naRead 14 October 2026SKU CP-9020270-NA. The EU and UK units are CP-9020270-EU and CP-9020270-UK, listed on Corsair's German page and by UK retailers with the same Tech Specs. The Japan unit is CP-9020270-JP and is not stored.10Retailer pagescan.co.uk/products/850w-corsair-rmx-series-rm850x-black-fully-modular-cybenetics-gold-pcie-51-single-rail-140mm-fan-atxRead 14 October 2026Scan lists CP-9020270-UK.

Century II 1200W1Maker product pagemontechpc.com/century-ii-1200wRead 14 October 2026Specifications tab: Model Name Century II 1200W. The maker prints no part number.

GTIN / EAN

840006667506, 840006667445, 8400066675448Spec databasecomparateur-gamer.fr/prix/corsair-rm850x-2024-840006667445Read 14 October 2026EAN 840006667445 with reference CP-9020270-EU.9Retailer pageebay.com/p/22074154707Read 14 October 2026eBay product page for CP-9020270-NA shows UPC 0840006667506. This is the only source for the NA code. The check digit is valid.10Retailer pagescan.co.uk/products/850w-corsair-rmx-series-rm850x-black-fully-modular-cybenetics-gold-pcie-51-single-rail-140mm-fan-atxRead 14 October 2026Scan lists manufacturer code CP-9020270-UK with GTIN 840006667544.

47105627463651Maker product pagemontechpc.com/century-ii-1200wRead 14 October 2026Specifications tab: EAN 4710562746365.

AnnouncediThe maker's first announcement of this model. This is separate from first retail availability.

10 September 20244Press releasecorsair.com/newsroom/press-release/corsair-updates-popular-rmx-series-low-noise-power-supplies-with-atx-3-1-compliance-and-native-atx-12v-2x6-connectorRead 14 October 2026Press release dated September 10, 2024.

15 April 20252Press articlefunkykit.com/news/montech-introduces-century-ii-power-supplyRead 14 October 2026Article dated 2025-04-15. It says the line is available on April 15, 2025 at 9 AM Eastern Time.

Status

Available1Maker product pagecorsair.com/us/en/p/psu/cp-9020270-na/rmx-series-rm850x-fully-modular-power-supply-cp-9020270-naRead 14 October 2026Page shows the product in stock.

Available6Retailer pagemaxmybuild.com/power-supplies/montech-century-ii-1200wRead 14 October 2026Listing shows $159.90 at Amazon and Newegg, both in stock, updated 14 Oct 2026. This is a current selling price, not the launch price.

PredecessoriThe model this one directly replaced, in the same line, tier and size, as the maker or a trusted review names it.

Not available

Not available

SuccessoriThe model that directly replaced this one, in the same line, tier and size. A revision such as a Slim or OLED model does not count when a next generation exists.

Not available

Not available

Launch price (US)iThe maker's US launch MSRP for the stated configuration, excluding tax. Current store prices and later discounts do not qualify.

$149.993Maker product pageweb.archive.org/web/20240913090852/https://www.corsair.com/us/en/p/psu/cp-9020270-na/rmx-series-rm850x-fully-modular-power-supply-cp-9020270-naRead 14 October 2026Archived copy of the Corsair US page from 2024-09-13, three days after launch. It shows a regular price of 149.99 USD with no discount, excluding sales tax. Hardware Busters gives an MSRP of 150 USD excluding VAT. TweakTown prints 169.99 USD, which is the later list price on Corsair's page today.6Reviewhwbusters.com/psus/corsair-rm850x-atx-v3-1-psu-reviewRead 14 October 2026Technical specifications: MSRP (excluding VAT) 150 USD. Review published September 14, 2024.

$129.92Press articlefunkykit.com/news/montech-introduces-century-ii-power-supplyRead 14 October 2026CENTURY II 1200 W: US$ 129.9. US price, no sales tax. KitGuru's launch article prints $129.99 and Hardware Busters prints an MSRP of $130 excluding VAT.5Reviewhwbusters.com/psus/montech-century-ii-1200w-atx-v3-1-psu-reviewRead 14 October 2026Technical specifications: MSRP (excluding VAT) $130. The stored value is the maker's launch price from the Funkykit report.

Launch price (EU)iThe maker's euro launch price for the stated configuration, including VAT as published. Current store prices and later discounts do not qualify.

Not available

Not available

MarketsiISO country or region codes where this exact model or variant is sold. A source page's language does not establish availability.

Not available

Not available

ColoursiThe maker's own colour names

Not available

Metallic Silver1Maker product pagemontechpc.com/century-ii-1200wRead 14 October 2026Overview text: a sleek metallic silver finish. The maker names no other colour.

Form factoriThe physical size standard that decides what fits in the case. An ATX unit is 150 × 86 mm at the back. An SFX unit is 125 × 63.5 mm.

ATX1Maker product pagecorsair.com/us/en/p/psu/cp-9020270-na/rmx-series-rm850x-fully-modular-power-supply-cp-9020270-naRead 14 October 2026Tech Specs: Dimensions 160x150x86. The back face is 150 x 86 mm, the standard ATX size.

ATX1Maker product pagemontechpc.com/century-ii-1200wRead 14 October 2026Specifications tab: Form Factor ATX (140).3Measurementcybenetics.com/evaluations/psus/2808Read 14 October 2026DUT Information: Type ATX12V. The maker lists form factor ATX (140).

ATX versioniThe ATX12V design guide revision the maker claims compliance with. A 16-pin GPU cable alone does not establish ATX 3.x. A Cybenetics report that withholds its ATX badge does not change the maker's claim. It goes in the source note.

ATX 3.11Maker product pagecorsair.com/us/en/p/psu/cp-9020270-na/rmx-series-rm850x-fully-modular-power-supply-cp-9020270-naRead 14 October 2026Tech Specs: ATX12V Version 3.1.

ATX 3.11Maker product pagemontechpc.com/century-ii-1200wRead 14 October 2026Overview: built to ATX 3.1 and PCIe 5.1 platforms. The 80 PLUS certificate type line reads ATX 3.0, ATX 3.1.

PCIe CEM versioniThe PCI Express card power revision the maker claims, as printed next to the ATX version. It sets the GPU power connector rules. It is not a slot speed. A reviewer's statement is not enough.

PCIe 5.11Maker product pagecorsair.com/us/en/p/psu/cp-9020270-na/rmx-series-rm850x-fully-modular-power-supply-cp-9020270-naRead 14 October 2026Feature list: ATX 3.1 compliant, supporting PCIe 5.1.

PCIe 5.11Maker product pagemontechpc.com/century-ii-1200wRead 14 October 2026Overview: built to ATX 3.1 and PCIe 5.1 platforms, with a standard 12V-2x6 cable.

Modular cablesiFull means every cable detaches. Semi means some cables are fixed, usually the 24-pin and CPU cables.

Fully modular1Maker product pagecorsair.com/us/en/p/psu/cp-9020270-na/rmx-series-rm850x-fully-modular-power-supply-cp-9020270-naRead 14 October 2026

Fully modular1Maker product pagemontechpc.com/century-ii-1200wRead 14 October 2026Overview: a fully modular design with included flat cables.3Measurementcybenetics.com/evaluations/psus/2808Read 14 October 2026DUT Information: Cable Design Fully Modular.

Built by (OEM)iThe company that designed and built the unit for the brand, such as CWT or FSP. As named by the maker, a teardown review or a Cybenetics report.

Channel Well Technology (CWT)5Measurementcybenetics.com/evaluations/psus/2399Read 14 October 2026DUT Information: OEM/ODM Channel Well Technology. Parts description: Manufacturer (OEM) CWT.6Reviewhwbusters.com/psus/corsair-rm850x-atx-v3-1-psu-reviewRead 14 October 2026Technical specifications: OEM Channel Well Technology (CWT).

Shenzhen Xinweiye Technology (XWY)3Measurementcybenetics.com/evaluations/psus/2808Read 14 October 2026DUT Information: OEM/ODM Shenzhen Xinweiye Technology Co., Ltd. Hardware Busters names the same company.5Reviewhwbusters.com/psus/montech-century-ii-1200w-atx-v3-1-psu-reviewRead 14 October 2026Technical specifications: Manufacturer (OEM) Shenzhen Xinweiye Technology.

Power

5 of 9 differ

Rated continuous poweriThe continuous DC output the maker rates the unit for, such as 850. Peak or power excursion figures are not stored here.

850W1Maker product pagecorsair.com/us/en/p/psu/cp-9020270-na/rmx-series-rm850x-fully-modular-power-supply-cp-9020270-naRead 14 October 2026Tech Specs: Continuous Power W 850 Watts.

1,200W1Maker product pagemontechpc.com/century-ii-1200wRead 14 October 2026Specifications tab: Wattage 1200, Total Power 1200W.3Measurementcybenetics.com/evaluations/psus/2808Read 14 October 2026Manufacturer-provided information: Rated Power 1200 W.

Full power rated up toiThe ambient temperature up to which the maker rates full continuous power, such as 50 °C. A review table that prints 0-50 °C with no maker source is not enough. An operating temperature range that does not say full power is not enough. A maker table with load steps gives the full-load row, such as 40 °C at full load next to 50 °C at 80 percent load. A temperature that a Cybenetics report marks as manufacturer-provided counts as a maker statement.

50°C1Maker product pagecorsair.com/us/en/p/psu/cp-9020270-na/rmx-series-rm850x-fully-modular-power-supply-cp-9020270-naRead 14 October 2026Overview: 50 C continuous operating temperature. The press release rates the power output at a 50 C ambient temperature.4Press releasecorsair.com/newsroom/press-release/corsair-updates-popular-rmx-series-low-noise-power-supplies-with-atx-3-1-compliance-and-native-atx-12v-2x6-connectorRead 14 October 2026Rated power output at a 50 C ambient temperature.

Not available

12V rail designiHow the maker splits +12V over-current protection. Switchable means the user picks single or multi rail with a switch or in software.

Single rail6Reviewhwbusters.com/psus/corsair-rm850x-atx-v3-1-psu-reviewRead 14 October 2026Technical specifications: 12V combined 850W on 1 12V rail.

Single rail3Measurementcybenetics.com/evaluations/psus/2808Read 14 October 2026Power Specifications: one +12V column with 100A and 1200W.5Reviewhwbusters.com/psus/montech-century-ii-1200w-atx-v3-1-psu-reviewRead 14 October 2026Technical specifications: Number of 12V rails 1.

+12V max currentiHighest combined current on +12V from the maker's power table. For a multi-rail unit this is the combined total, not one rail.

70.8A1Maker product pagecorsair.com/us/en/p/psu/cp-9020270-na/rmx-series-rm850x-fully-modular-power-supply-cp-9020270-naRead 14 October 2026Power table: +12V 70.8A, 849.6W, model RPS0197, part no. 75-005876.2Owner's manualcorsair.com/us/en/explorer/diy-builder/power-supply-units/corsair-rmx-seriesRead 14 October 2026RM850x power table: +12V 70.8A, 849.6W, model RPS0197.

100A1Maker product pagemontechpc.com/century-ii-1200wRead 14 October 2026DC Output table: +12V 100A, 1200W.3Measurementcybenetics.com/evaluations/psus/2808Read 14 October 2026Power Specifications: +12V 100A, 1200W.

+12V max poweriHighest combined power on +12V from the maker's power table.

849.6W1Maker product pagecorsair.com/us/en/p/psu/cp-9020270-na/rmx-series-rm850x-fully-modular-power-supply-cp-9020270-naRead 14 October 2026Power table: +12V 70.8A, 849.6W.2Owner's manualcorsair.com/us/en/explorer/diy-builder/power-supply-units/corsair-rmx-seriesRead 14 October 2026RM850x power table: +12V 70.8A, 849.6W.

1,200W1Maker product pagemontechpc.com/century-ii-1200wRead 14 October 2026DC Output table: +12V 100A, 1200W.3Measurementcybenetics.com/evaluations/psus/2808Read 14 October 2026Power Specifications: +12V 1200W.

+3.3V and +5V combined poweriThe combined limit for the +3.3V and +5V rails from the maker's power table. A table that prints the same figure under both rails, as be quiet! does, shows one shared limit, so the figure is stored once and not added.

150W1Maker product pagecorsair.com/us/en/p/psu/cp-9020270-na/rmx-series-rm850x-fully-modular-power-supply-cp-9020270-naRead 14 October 2026Power table: +3.3V 20A and +5V 20A with one 150W cell.2Owner's manualcorsair.com/us/en/explorer/diy-builder/power-supply-units/corsair-rmx-seriesRead 14 October 2026RM850x power table: +3.3V 20A and +5V 20A, 150W.

100W1Maker product pagemontechpc.com/century-ii-1200wRead 14 October 2026DC Output table prints +3.3V 20A and +5V 20A with one 100W cell. The Cybenetics power table has one merged 100W cell for 3.3V and 5V, so 100W is the combined limit.3Measurementcybenetics.com/evaluations/psus/2808Read 14 October 2026Power Specifications: one merged 100W cell for 3.3V and 5V, 20A each.

+5V standby currentiHighest current on the +5VSB standby rail. It powers USB charging and wake functions while the PC is off.

3A1Maker product pagecorsair.com/us/en/p/psu/cp-9020270-na/rmx-series-rm850x-fully-modular-power-supply-cp-9020270-naRead 14 October 2026Power table: +5VSB 3A, 15W.2Owner's manualcorsair.com/us/en/explorer/diy-builder/power-supply-units/corsair-rmx-seriesRead 14 October 2026RM850x power table: +5Vsb 3A, 15W.

3A1Maker product pagemontechpc.com/century-ii-1200wRead 14 October 2026DC Output table: +5VSB 3A, 15W.3Measurementcybenetics.com/evaluations/psus/2808Read 14 October 2026Power Specifications: 5VSB 3A, 15W.

AC input voltageiThe rated AC input range, such as 100 to 240 V.

Lowest100Highest240V1Maker product pagecorsair.com/us/en/p/psu/cp-9020270-na/rmx-series-rm850x-fully-modular-power-supply-cp-9020270-naRead 14 October 2026Power table: AC input 100-240V, input current 10A-5A, 47-63Hz.2Owner's manualcorsair.com/us/en/explorer/diy-builder/power-supply-units/corsair-rmx-seriesRead 14 October 2026Power table: AC input rating 100V-240V, input current 10A-5A, 47Hz-63Hz.

Lowest100Highest240V1Maker product pagemontechpc.com/century-ii-1200wRead 14 October 2026AC Input 100-240Vac 50-60Hz 15A-10A.3Measurementcybenetics.com/evaluations/psus/2808Read 14 October 2026Manufacturer-provided information: 100-240 Vrms, 15 A, 50-60 Hz.

Alternative low power mode (ALPM)iThe maker or a Cybenetics report states support for the ATX alternative low power mode used by Modern Standby.

Yes1Maker product pagecorsair.com/us/en/p/psu/cp-9020270-na/rmx-series-rm850x-fully-modular-power-supply-cp-9020270-naRead 14 October 2026Tech Specs: Modern Standby Yes. The Cybenetics report ticks ALPM compatible.5Measurementcybenetics.com/evaluations/psus/2399Read 14 October 2026Temperature and Compliance Info: ALPM (Alternative Low Power Mode) compatible, checked.

Yes3Measurementcybenetics.com/evaluations/psus/2808Read 14 October 2026Temperature and Compliance Info: ALPM compatible, checked.

Certifications

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80 PLUS ratingiThe 80 PLUS level. When the 80 PLUS listing or certificate and the maker claim differ, store the listing level and put the claim and test voltage in the source note. When a model has several 80 PLUS entries, such as a newer test at a higher level, use the newest entry that matches the current maker documents.

Not available

80 PLUS Gold4Certification listclearesult.com/80plus/sites/80plus/files/manufacturer-certificate/MONTECH_CENTURY%20II%201200W_1200W_SOCE%207852_Report.pdfRead 14 October 202680 PLUS ID 7852, model CENTURY II 1200W, type ATX 3.0, ATX 3.1, 1200 W, 115V Internal, Gold, test date 2025-06-04. The certificate lists no sample serial. The maker's own page says Platinum, which is the Cybenetics level.

Cybenetics efficiency at 115ViThe Cybenetics ETA level from the 115V test. The Cybenetics report wins over the maker's claim.

Cybenetics Gold5Measurementcybenetics.com/evaluations/psus/2399Read 14 October 2026Report 24PS2399A, certification ID 252399, issued Apr 1, 2024. The ETA badge shows Gold at 115V. The model name is RM850x (ATX v3.1). Corsair also says Cybenetics Gold without a voltage.

Cybenetics Platinum3Measurementcybenetics.com/evaluations/psus/2808Read 14 October 2026Report 25PS2808A, certification ID 252808, issued May 13, 2025. The database name is Montech Century II Gold 1200 ATX3. The badge is ETA Platinum at 115V, as Hardware Busters also prints. The 80 PLUS certificate says Gold.

Cybenetics efficiency at 230ViThe Cybenetics ETA level from the 230V test. The 230V thresholds are higher, so the level can differ from the 115V level. The Cybenetics report wins over the maker's claim.

Cybenetics Gold5Measurementcybenetics.com/evaluations/psus/2399Read 14 October 2026The ETA badge shows Gold at 230V.

Cybenetics Platinum3Measurementcybenetics.com/evaluations/psus/2808Read 14 October 2026ETA Platinum at 230V (badge image, and Hardware Busters prints Platinum).

Cybenetics noise at 115ViThe Cybenetics LAMBDA level from the 115V test. A++ is the quietest. The Cybenetics report wins over the maker's claim.

A1Maker product pagecorsair.com/us/en/p/psu/cp-9020270-na/rmx-series-rm850x-fully-modular-power-supply-cp-9020270-naRead 14 October 2026Tech Specs: Cybenetics Noise A, with no input voltage. The Cybenetics report shows A at both voltages. The launch press release says A+, which the report does not show.5Measurementcybenetics.com/evaluations/psus/2399Read 14 October 2026The LAMBDA badge shows A at 115V.

Standard++3Measurementcybenetics.com/evaluations/psus/2808Read 14 October 2026LAMBDA Standard++ at 115V (badge image). The 115V average of 30.37 dBA is above the A- band of 25-30 dBA. Hardware Busters prints A- (25-30 dB(A)), which matches the 230V result.

Cybenetics noise at 230ViThe Cybenetics LAMBDA level from the 230V test. The Cybenetics report wins over the maker's claim.

A1Maker product pagecorsair.com/us/en/p/psu/cp-9020270-na/rmx-series-rm850x-fully-modular-power-supply-cp-9020270-naRead 14 October 2026Tech Specs: Cybenetics Noise A, with no input voltage. The Cybenetics report shows A at both voltages.5Measurementcybenetics.com/evaluations/psus/2399Read 14 October 2026The LAMBDA badge shows A at 230V.

A-3Measurementcybenetics.com/evaluations/psus/2808Read 14 October 2026LAMBDA A- at 230V (badge image), average 29.44 dBA.

Measured

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Average efficiency at 115V (measured)iAverage efficiency over the whole load range at 115V input, from more than 1450 load combinations in the Cybenetics method. It is not the peak efficiency or the efficiency at 50% load.

88.815%5Measurementcybenetics.com/evaluations/psus/2399Read 14 October 2026Average over more than 1450 load combinations at 115V. Tested Mar 29, 2024 on sample serial A6GGA404K007EE, received Mar 14, 2024. Ambient 28-32 C. DUT note: CP-9020270 (Semi-Passive Off).

89.94%3Measurementcybenetics.com/evaluations/psus/2808Read 14 October 2026Average over more than 1450 load combinations at 115V. Sample received Apr 29, 2025, tested May 8, 2025, ambient 28-32 C. The report lists no sample serial.

Average efficiency at 230V (measured)iThe same average efficiency at 230V input.

90.944%5Measurementcybenetics.com/evaluations/psus/2399Read 14 October 2026Average over more than 1450 load combinations at 230V.

92.169%3Measurementcybenetics.com/evaluations/psus/2808Read 14 October 2026Average over more than 1450 load combinations at 230V.

Light-load efficiency at 115V (measured)iEfficiency at a 10 W load for units up to 500 W, or at a 2% load for larger units, at 115V input. This is the ATX light-load test.

75.825%5Measurementcybenetics.com/evaluations/psus/2399Read 14 October 2026Efficiency at 2% load (more than 500 W unit) at 115V.

65.28%3Measurementcybenetics.com/evaluations/psus/2808Read 14 October 2026Efficiency at 2% load (more than 500 W unit) at 115V. At 230V it is 74.640%.

Average power factor at 115V (measured)iAverage power factor over the whole load range at 115V input. 1 is the best possible value.

0.995Measurementcybenetics.com/evaluations/psus/2399Read 14 October 2026Average over more than 1450 load combinations at 115V.

0.9843Measurementcybenetics.com/evaluations/psus/2808Read 14 October 2026Average over more than 1450 load combinations at 115V. At 230V it is 0.957.

Average noise at 115V (measured)iAverage noise over the whole load range at 115V input in the Cybenetics method, at about 30 °C ambient. It is not the noise at full load.

21.34dB(A)5Measurementcybenetics.com/evaluations/psus/2399Read 14 October 2026Average over more than 1450 load combinations at 115V. Ambient 28-32 C. Bruel and Kjaer 2270 G4 sound analyzer. The DUT note says semi-passive off, but the typical load table shows the fan at 0 rpm from 10% to 50% load, so the report does not make clear whether the fan ran in every part of the average. The 230V average is 21.37 dBA.

30.37dB(A)3Measurementcybenetics.com/evaluations/psus/2808Read 14 October 2026Average over more than 1450 load combinations at 115V, ambient 28-32 C, Bruel and Kjaer 2270 G4 sound analyzer. The 230V average is 29.44 dBA. The fan ran at 1030 rpm at 10% load in the typical load tests, so the semi-passive mode was not active during them. The report marks semi-passive operation as selectable.

Noise at full load at 115V (measured)iNoise at 100% load at 115V input in the Cybenetics typical load tests. That row often runs at about 45 °C intake. The intake temperature and the fan speed go in the source note. Lower is better.

30.8dB(A)5Measurementcybenetics.com/evaluations/psus/2399Read 14 October 2026Typical load tests at 115V, 100% load row: 30.8 dB(A) at 986 rpm fan speed, ambient about 30 C. At 230V it is also 30.8 dB(A) at 986 rpm.

45.1dB(A)3Measurementcybenetics.com/evaluations/psus/2808Read 14 October 2026Typical load tests at 115V, 100% load row: 45.1 dB(A) at 1912 rpm fan speed, ambient about 30 C. At 230V it is 41.5 dB(A) at 1864 rpm.

Standby power with no load at 115V (measured)iPower the unit draws from the wall with the PC off and nothing drawn from +5VSB, at 115V input.

0.0179W5Measurementcybenetics.com/evaluations/psus/2399Read 14 October 2026Standby power consumption at 115V with no load on +5VSB.

0.0521W3Measurementcybenetics.com/evaluations/psus/2808Read 14 October 2026Standby power consumption at 115V with no load on +5VSB: 0.0521 W. At 230V it is 0.0959 W.

Hold-up time (measured)iHow long the outputs stay in regulation after AC power is lost, at maximum continuous load, as printed in the Cybenetics report. The report names no input voltage. The AC loss to PWR_OK time goes in the source note. Higher is better.

25ms5Measurementcybenetics.com/evaluations/psus/2399Read 14 October 2026Hold-Up Time and PWR_OK Signal: hold-up time 25.00 ms, AC loss to PWR_OK 21.30 ms, PWR_OK inactive to DC loss 3.70 ms, at maximum continuous load. The report names no input voltage.

24ms3Measurementcybenetics.com/evaluations/psus/2808Read 14 October 2026Hold-Up Time and PWR_OK Signal: hold-up time 24.0 ms, AC loss to PWR_OK 19.7 ms, PWR_OK inactive to DC loss 4.3 ms, at maximum continuous load. The report names no input voltage.

12V ripple at full load (measured)iPeak-to-peak ripple on the +12V rail at full load and 115V input. Lower is better.

24.2mV5Measurementcybenetics.com/evaluations/psus/2399Read 14 October 2026Non-accredited measurement. 12V ripple at full load at 115V. At 230V it is 25.82 mV.

19.68mV3Measurementcybenetics.com/evaluations/psus/2808Read 14 October 2026Non-accredited. 12V ripple at full load at 115V. At 230V it is 19.46 mV.

12V load regulation (measured)iHow far the +12V voltage moves between light and full load at 115V input. Lower is better.

0.63%5Measurementcybenetics.com/evaluations/psus/2399Read 14 October 2026Non-accredited measurement. 12V load regulation at 115V. At 230V it is 0.64%.

0.46%3Measurementcybenetics.com/evaluations/psus/2808Read 14 October 2026Non-accredited. 12V load regulation at 115V. At 230V it is 0.47%.

Cables and connectors

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CablesiOne row per kind of cable that runs from the PSU to a device. Connector is the plug at the device end. Count is the number of those plugs over all cables in the row. Length runs from the PSU end to the first plug. Adapters that plug into other cables are left out. Use 16-pin PCIe when the maker names a 16-pin GPU cable without saying 12V-2x6 or 12VHPWR. A cable from a 12V-2x6 socket on the PSU to 8-pin plugs is a cable, not an adapter, and counts as PCIe 8-pin. When the maker's documents name one GPU cable both 12VHPWR and 12V-2x6, use 16-pin PCIe and name both in the source note. Cables of one connector kind with different lengths or wire gauges get one row each.

ACORSAIR RM850x (2024)

Connector	Connectors	Cables	Length to first plug (mm)	Wire gauge	Rated power (W)
ATX 24-pin (20+4)	1	1	610	16-20AWG	Not available
CPU 8-pin (EPS, 4+4)	2	2	750	18AWG	Not available
PCIe 8-pin (6+2)	3	3	650	16-18AWG	Not available
12V-2x6	1	1	650	Not available	600
SATA power	8	2	505	18AWG	Not available
4-pin Molex	3	1	550	18AWG	Not available

Source1Maker product pagecorsair.com/us/en/p/psu/cp-9020270-na/rmx-series-rm850x-fully-modular-power-supply-cp-9020270-naRead 14 October 2026Cable listing: 1 ATX 24-pin 610 mm, 2 EPS 8-pin (4+4) 750 mm, 1 PCIe 12V-2x6 (12+4) 650 mm, 3 PCIe 8-pin (6+2) 650 mm, 2 SATA cables with 4 plugs each (505 mm to the first plug, 115 mm spacing, 850 mm total), 1 PATA cable with 3 plugs (550 mm to the first plug, 100 mm spacing, 750 mm total). All lengths have a tolerance of 10 mm, the PATA cable 25 mm. PATA plugs are the 4-pin Molex plugs. The page does not rate the 12V-2x6 cable. The Cybenetics report and Hardware Busters list it at 600 W. Gauges come from the Cybenetics report. The 16-24AWG range for the 12V-2x6 cable includes the thin sideband wires, so no gauge is stored for it. Cybenetics lists the SATA cable at 500 mm, which is not stored.2Owner's manualcorsair.com/us/en/explorer/diy-builder/power-supply-units/corsair-rmx-seriesRead 14 October 2026Included cables: 1x ATX 24-pin 610 mm, 2x EPS 8-pin (4+4) 750 mm, 1x PCIe 12V-2x6 (12+4) 650 mm, 3x PCIe 8-pin (6+2) 650 mm, 2x SATA with 4 plugs 850 mm, 1x PATA with 3 plugs 750 mm.5Measurementcybenetics.com/evaluations/psus/2399Read 14 October 2026Cables and Connectors table: ATX 16-20AWG, EPS 18AWG, 6+2 pin PCIe 16-18AWG, 12+2 pin PCIe (600W) 16-24AWG, SATA 18AWG and Molex 18AWG, no in-cable capacitors. The 12V-2x6 cable is listed at 650 mm.

BMontech Century II 1200W

Connector	Connectors	Cables	Length to first plug (mm)	Wire gauge	Rated power (W)
ATX 24-pin (20+4)	1	1	600	18AWG	Not available
CPU 8-pin (EPS, 4+4)	2	2	700	18AWG	Not available
PCIe 8-pin (6+2)	6	3	600	18AWG	Not available
12V-2x6	1	1	600	Not available	600
SATA power	12	3	500	18AWG	Not available
4-pin Molex	4	1	500	18AWG	Not available

Source1Maker product pagemontechpc.com/century-ii-1200wRead 14 October 2026Cables table: 1 motherboard cable with a 20+4 pin plug (600 mm), 2 CPU cables with one 4+4 pin plug each (700 mm), 3 PCIe cables with two 6+2 pin plugs each (600 mm), 1 12V-2x6 cable (600 mm), 3 SATA cables with 4 plugs each (950 mm to the last plug) and 1 Molex cable with 4 plugs (950 mm to the last plug). The first-plug lengths of the SATA and Molex cables (500 mm) and the gauge come from the Cybenetics report. The report measures the ATX cable at 595 mm, the maker table says 600 mm.3Measurementcybenetics.com/evaluations/psus/2808Read 14 October 2026Cables and Connectors table: ATX 20+4 pin 595 mm 18AWG, 2 x 4+4 pin EPS12V 700 mm 18AWG, 3 PCIe cables with 6+2 pin plugs (600 mm then 150 mm), 6 plugs in total, 18AWG, 12+4 pin PCIe 600 mm (600W) 16-26AWG, 3 SATA cables (500 mm plus 3 x 150 mm spacing) with 12 plugs in total 18AWG, 1 Molex cable (500 mm plus 3 x 150 mm) with 4 plugs 18AWG. The 16-26AWG range of the 12V-2x6 cable includes the thin sideband wires, so no gauge is stored for it.

CPU (EPS) connectorsi8-pin or 4+4-pin CPU power plugs.

2=CalculatedFrom Cables

2=CalculatedFrom Cables

PCIe 8-pin connectorsi8-pin or 6+2-pin GPU power plugs. Counts the plugs in the box. Some cables share one PSU socket, which the source note says.

3=CalculatedFrom Cables

6=CalculatedFrom Cables

16-pin GPU connectorsiNative 16-pin GPU power plugs: 12V-2x6, 12VHPWR and 16-pin cables of unstated revision. Adapters are not counted. Counts the plugs in the box. Some cables share one PSU socket, which the source note says.

1=CalculatedFrom Cables

1=CalculatedFrom Cables

SATA power connectors

8=CalculatedFrom Cables

12=CalculatedFrom Cables

4-pin Molex connectors

3=CalculatedFrom Cables

4=CalculatedFrom Cables

Cable styleiHow the modular cables are made. Mixed means some cables are sleeved and others flat, such as a sleeved 24-pin cable with flat other cables. From the maker page or a review photo page.

Embossed or debossed flat1Maker product pagecorsair.com/us/en/p/psu/cp-9020270-na/rmx-series-rm850x-fully-modular-power-supply-cp-9020270-naRead 14 October 2026Cable listing: Cable Type Embossed for every cable. The Tech Specs row says Type 4.4Press releasecorsair.com/newsroom/press-release/corsair-updates-popular-rmx-series-low-noise-power-supplies-with-atx-3-1-compliance-and-native-atx-12v-2x6-connectorRead 14 October 2026Fully modular, embossed, ultra-flexible cables.6Reviewhwbusters.com/psus/corsair-rm850x-atx-v3-1-psu-reviewRead 14 October 2026Cables page: all cables are embossed.

Flat1Maker product pagemontechpc.com/century-ii-1200wRead 14 October 2026Overview: flat cables and a fully modular design.5Reviewhwbusters.com/psus/montech-century-ii-1200w-atx-v3-1-psu-reviewRead 14 October 2026Cables page: all cables are flat and consist of black gauges. Review published May 30, 2025.

Fan

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Fan sizeiFrame size of the cooling fan, such as 120, 135 or 140.

140mm1Maker product pagecorsair.com/us/en/p/psu/cp-9020270-na/rmx-series-rm850x-fully-modular-power-supply-cp-9020270-naRead 14 October 2026Overview: 140mm low-noise fan.4Press releasecorsair.com/newsroom/press-release/corsair-updates-popular-rmx-series-low-noise-power-supplies-with-atx-3-1-compliance-and-native-atx-12v-2x6-connectorRead 14 October 2026140mm fan.5Measurementcybenetics.com/evaluations/psus/2399Read 14 October 2026Cooling: 140mm Fluid Dynamic Bearing Fan (NR140HP), 12V, 0.33A.

135mm1Maker product pagemontechpc.com/century-ii-1200wRead 14 October 2026Specifications tab: Fan Size 135mm.3Measurementcybenetics.com/evaluations/psus/2808Read 14 October 2026DUT Information: 135mm Fluid Dynamic Bearing Fan.

Fan bearingiUse the maker's bearing name. FDB and S-FDB are fluid dynamic. HDB is hydrodynamic. Noctua SSO and SSO2 are SSO. Corsair Magnetic Dome is magnetic dome. A brand bearing name that fits no option is Other.

Fluid dynamic (FDB)1Maker product pagecorsair.com/us/en/p/psu/cp-9020270-na/rmx-series-rm850x-fully-modular-power-supply-cp-9020270-naRead 14 October 2026Overview: a fluid dynamic bearing fan with magnetic dome structure. The Cybenetics report lists a Fluid Dynamic Bearing fan. The bearing is stored as fluid dynamic, since the maker names the dome as a structure of the fan and not as the bearing.4Press releasecorsair.com/newsroom/press-release/corsair-updates-popular-rmx-series-low-noise-power-supplies-with-atx-3-1-compliance-and-native-atx-12v-2x6-connectorRead 14 October 2026140mm fluid-dynamic bearing (FDB) fan.5Measurementcybenetics.com/evaluations/psus/2399Read 14 October 2026Cooling: Fluid Dynamic Bearing fan.

Fluid dynamic (FDB)1Maker product pagemontechpc.com/century-ii-1200wRead 14 October 2026Specifications tab: Bearing FDB.3Measurementcybenetics.com/evaluations/psus/2808Read 14 October 2026DUT Information: 135mm Fluid Dynamic Bearing Fan (HA13525H12F-Z).

Fan modeiSemi-passive means the fan stops at low load, often sold as zero RPM, hybrid or 0 dB mode. Fanless means the unit has no fan.

Semi-passive1Maker product pagecorsair.com/us/en/p/psu/cp-9020270-na/rmx-series-rm850x-fully-modular-power-supply-cp-9020270-naRead 14 October 2026Tech Specs: Zero RPM Mode Yes. The fan is off at low to medium loads.5Measurementcybenetics.com/evaluations/psus/2399Read 14 October 2026Semi-Passive Operation checked and selectable.

Semi-passive1Maker product pagemontechpc.com/century-ii-1200wRead 14 October 2026Overview: 135mm fan with Smart Zero Fan mode.3Measurementcybenetics.com/evaluations/psus/2808Read 14 October 2026DUT Information: Semi-Passive Operation checked (selectable).

Fan mode switchiA button, switch or software setting lets the user turn the semi-passive mode off so the fan always spins. A unit without a semi-passive mode, whose fan the maker says always spins, has no switch, so it is false.

Not available

Yes3Measurementcybenetics.com/evaluations/psus/2808Read 14 October 2026DUT Information: Semi-Passive Operation marked selectable.5Reviewhwbusters.com/psus/montech-century-ii-1200w-atx-v3-1-psu-reviewRead 14 October 2026Product photos page: on the front side, besides the power switch, a smaller switch turns the fan's semi-passive operation on and off.

Protection and parts

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ProtectionsiProtections the maker lists, or a retailer spec table copies from the maker, plus protections the Cybenetics protection tests show working (UVP, NLO, SIP). The Cybenetics manufacturer list has no OVP or UVP row, so do not build the list from it alone. A protection that is not listed may still exist. No-load covers no-load operation and no-load protection. Fan failure is a maker's fan failure protection or fan safeguard, also when the Cybenetics manufacturer block lists it.

Over-current (OCP), Over-voltage (OVP), Under-voltage (UVP), Over-power (OPP), Over-temperature (OTP), Short-circuit (SCP), No-load (NLO), Surge and inrush (SIP)2Owner's manualcorsair.com/us/en/explorer/diy-builder/power-supply-units/corsair-rmx-seriesRead 14 October 2026Protections section: OVP and UVP on 12V, 5V and 3.3V, OCP on 3.3V, 5V and 12V, OTP, SCP and OPP. The six maker protections are stored together with NLO and SIP from the Cybenetics tests.6Reviewhwbusters.com/psus/corsair-rm850x-atx-v3-1-psu-reviewRead 14 October 2026Protection Features page, which presents the Cybenetics protection tests: OCP, OPP, OTP, SCP, NLO, fan failure protection and SIP (surge MOV, inrush NTC thermistor and bypass relay) all shown. The page has no OVP or UVP row.

Over-current (OCP), Over-voltage (OVP), Under-voltage (UVP), Over-power (OPP), Over-temperature (OTP), Short-circuit (SCP), No-load (NLO), Surge and inrush (SIP)1Maker product pagemontechpc.com/century-ii-1200wRead 14 October 2026Specifications tab: OPP / OVP / UVP / SCP / OCP / OTP. NLO and SIP come from the Cybenetics protection tests.3Measurementcybenetics.com/evaluations/psus/2808Read 14 October 2026Protection Features (Manufacturer) lists OPP, +12V OCP, OTP, SCP, surge and inrush current protection. Protection tests tick UVP at 90 V and 80 V and NLO, and SIP shows an MOV for surge and an NTC with bypass relay for inrush. The maker lists OVP, which the report does not test.

All-Japanese capacitorsiThe maker states that every electrolytic capacitor is from a Japanese maker. A Japanese bulk capacitor alone is not enough. A spec row such as "Japanese capacitors" that names no exception counts.

Yes1Maker product pagecorsair.com/us/en/p/psu/cp-9020270-na/rmx-series-rm850x-fully-modular-power-supply-cp-9020270-naRead 14 October 2026Overview: 100% industrial-grade, 105 C rated Japanese electrolytic capacitors.4Press releasecorsair.com/newsroom/press-release/corsair-updates-popular-rmx-series-low-noise-power-supplies-with-atx-3-1-compliance-and-native-atx-12v-2x6-connectorRead 14 October 2026100% Japanese electrolytic capacitors.

Yes1Maker product pagemontechpc.com/century-ii-1200wRead 14 October 2026Overview: 100% Japanese capacitors in the power architecture. The Cybenetics parts list also names 6 CapXon and 33 Chemi-Con polymer capacitors. CapXon is not a Japanese maker, so the claim may cover the electrolytic capacitors only.

MTBF (claimed)iThe maker's mean time between failures, such as 100000. An MTTF figure for the whole unit counts too. An MTTF for the fan alone does not. The test temperature goes in the source note.

100,000h1Maker product pagecorsair.com/us/en/p/psu/cp-9020270-na/rmx-series-rm850x-fully-modular-power-supply-cp-9020270-naRead 14 October 2026Tech Specs: MTBF Hours 100,000 hours. The test temperature is not stated.

Not available

Monitoring and lighting

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Software monitoringiThe unit reports power, temperature or fan data to PC software over a USB or internal connection.

Not available

Not available

SoftwareiThe maker's software for monitoring or control.

Not available

Not available

Built-in power displayiA screen on the unit that shows live power draw or other readings.

Not available

Not available

RGB lighting

Not available

No6Retailer pagemaxmybuild.com/power-supplies/montech-century-ii-1200wRead 14 October 2026Listing specs: RGB No. The maker page and Hardware Busters describe no lighting.

Dimensions and weight

2 of 2 differ

DimensionsiBody without cables. Width and height are the back face with the AC inlet. Depth is the length into the case, which decides case fit.

Width150Height86Depth160mm(5.9 × 3.4 × 6.3 in)1Maker product pagecorsair.com/us/en/p/psu/cp-9020270-na/rmx-series-rm850x-fully-modular-power-supply-cp-9020270-naRead 14 October 2026Tech Specs: 160x150x86 with no unit. The manual gives length 160 mm, width 150 mm and height 86 mm. Depth is 160 mm.2Owner's manualcorsair.com/us/en/explorer/diy-builder/power-supply-units/corsair-rmx-seriesRead 14 October 2026RM850x specifications: length 160 mm, width 150 mm, height 86 mm.

Width150Height86Depth140mm(5.9 × 3.4 × 5.5 in)1Maker product pagemontechpc.com/century-ii-1200wRead 14 October 2026Specifications tab: Dimensions (L*W*H) 140*150*86mm, so depth 140, width 150, height 86. The page also prints Operating Temperature 0-40 C, which is not stored. Hardware Busters prints 0-50 C for continuous full load.

WeightiWeight of the unit alone. Use the Hardware Busters figure on hwbusters.com when the maker states none, not a copy on another site. Maker weights that include cables or the box, such as Corsair's, and retailer packed weights are not stored. A net weight counts unless the maker says it includes the cables.

1.79kg(3.9 lb)6Reviewhwbusters.com/psus/corsair-rm850x-atx-v3-1-psu-reviewRead 14 October 2026Technical specifications: 1.79 kg (3.95 lb). Corsair's 3 kg figure is not stored, since it is most likely a packed weight.7Reviewigorslab.de/en/corsair-rm850x-atx-v3-1-power-supply-2024-testRead 14 October 2026Igor's Lab copy of the Hardware Busters review, published November 6, 2024. It lists 1.79 kg and 150 x 85 x 160 mm. The maker's 86 mm height is stored.

1.53kg(3.4 lb)5Reviewhwbusters.com/psus/montech-century-ii-1200w-atx-v3-1-psu-reviewRead 14 October 2026Technical specifications: 1.53 kg (3.37 lb). The review does not say whether cables are included. Montech does not publish a weight.

In the box

None of 1 known

In the boxiItems supplied with this exact model, verbatim. The AC power cord differs per region.

Not available

Not available

Links

Not compared

Product page

www.corsair.com/us/en/p/psu/cp-9020270-na/rmx-series-rm850x-fully-modular-power-supply-cp-9020270-na1Maker product pagecorsair.com/us/en/p/psu/cp-9020270-na/rmx-series-rm850x-fully-modular-power-supply-cp-9020270-naRead 14 October 2026

www.montechpc.com/century-ii-1200w1Maker product pagemontechpc.com/century-ii-1200wRead 14 October 2026

Spec sheet

Not available

Not available

Manual

www.corsair.com/us/en/explorer/diy-builder/power-supply-units/corsair-rmx-series2Owner's manualcorsair.com/us/en/explorer/diy-builder/power-supply-units/corsair-rmx-seriesRead 14 October 2026

Not available

EPREL registration numberiId in the EU energy label database. Each size or model of a series has its own id, so it is per variant.

Not available

Not available

Warranty

0 of 1 differ

Manufacturer warranty (source market)iThe maker's warranty period for the exact SKU or configuration and market named in the source note. It applies only to that stated market, not every regional variant. Statutory consumer rights are excluded. The base term is stored. An extension that needs registration goes in the source note.

10years1Maker product pagecorsair.com/us/en/p/psu/cp-9020270-na/rmx-series-rm850x-fully-modular-power-supply-cp-9020270-naRead 14 October 2026Tech Specs: Warranty 10 Year. The page is corsair.com US, so the market is US.

10years1Maker product pagemontechpc.com/century-ii-1200wRead 14 October 2026Specifications tab: Warranty 10 Years. The page is the global maker page and names no market.

Both are also in the API. Back to all power supplies.