Corsair SF850 Platinum SFX (CP-9020256)

The Corsair SF850 Platinum is an 850 W power supply in the compact SFX form factor, part of Corsair's SF Platinum Series and sold under the part number CP-9020256. Corsair's pitch is Platinum power for small-form-factor builds: an SFX unit rated for 80 PLUS Platinum efficiency that is meant for the most power-dense small PCs. The manufacturer page shows a price, but it sits next to a selector that offers 750, 850 and 1000 W versions, so we cannot be certain it applies to this capacity and we leave the price empty. This entry summarises the published electrical table, cable list and features, adds arithmetic checks, and points out the places where the page uses two names for the same thing. The unit has not been measured by us.

Ratings and rails

The power table lists the model code RPS0175 and the part number 75-005385. The AC input is 100 to 240 V at 10 to 5 A and 47 to 63 Hz. On the output side, the +12 V rail is rated for 70.8 A and 850 W, the +3.3 V and +5 V rails for 20 A each with a combined limit of 130 W, and the +5VSB standby output for 3 A and 15 W; total power is 850 W. A quick check: 70.8 A multiplied by 12 V is 849.6 W, so essentially the whole rating is on the +12 V rail (arithmetic from the table, and the same 70.8 A figure appears for the 850 W unit in our RM850x entry). Corsair also states a continuous output rating at 50 degrees Celsius, which matters in small cases where the air around the power supply is warm. If you are working out how much power your build needs, our PSU wattage guide is a good starting point, but note that 850 W in an SFX case is a generous allowance for most single-GPU systems.

Standards and efficiency

The unit carries 80 PLUS Platinum certification, and the tech spec lists Cybenetics efficiency Platinum and Cybenetics noise A-. The ATX12V version is 3.1 and Corsair says the SF Series is formally certified for ATX 3.1 compliance, with a PCIe 5.1 12V-2x6 graphics cable included for modern cards. The EPS12V version is listed as 2.92. One naming note: the feature text calls the graphics cable a 12V-2x6 cable, while the cable table names the connector 12VHPWR (12+4 pin); both refer to the high-power graphics connector family explained in our page on the 12VHPWR power connector. Corsair lists 105 degree rated, industrial-grade Japanese electrolytic capacitors and a mean time between failures of 100,000 hours.

Cooling and noise

The fan is a 92 mm PWM model with a fluid dynamic bearing, and the unit has a Zero RPM mode, which Corsair says removes fan noise completely at low to medium loads. A smaller fan has to work harder than a 120 or 140 mm fan at high load, which is the general trade-off of the SFX format, so the Cybenetics noise grade of A- is worth noting: it is the grade the page lists, and it is a measured-noise classification, not a decibel number. The page does not give decibel figures or a fan curve, so we do not either.

Cables and connectors

Corsair publishes a precise cable list, and every cable is individually sleeved. The 24-pin ATX cable is 300 mm. There are two EPS/ATX12V 8-pin (4+4) cables at 400 mm, three separate PCIe 8-pin (6+2) cables at 400 mm, one 12VHPWR cable at 400 mm, one SATA cable with four straight connectors and one with four right-angle connectors, both 445 mm, and one PATA cable with three connectors at 330 mm. The tech spec totals eight SATA connectors and three PATA connectors. The cables use Type 5 Micro-Fit connectors on the power-supply side, which is the SFX-style modular standard and differs from the Type 4 cables used on Corsair's larger units, so cables are not interchangeable between the two families. The short lengths suit small cases, but check them against your layout: three separate PCIe cables at 400 mm reach a bottom-mounted power supply in a compact tower, but a case with a rear or side-mounted power supply may need more length. Our guide to SFX versus ATX power supplies discusses these form-factor questions.

Where it sits in our database

The closest relatives are two other SFX units. The Corsair SF600 Platinum is the same family at 600 W, with a 92 mm rifle-bearing fan, ATX12V v2.4 and a seven-year warranty. The Cooler Master V850 SFX Gold also offers 850 W in SFX with a 92 mm fluid dynamic bearing fan, but at 80 PLUS Gold and with a ten-year warranty. Between the two 850 W SFX units, the SF850 Platinum gives higher rated efficiency and a newer standard (ATX 3.1 against SFX 12V v3.42 on the other), and the V850 gives three extra years of warranty. You can see every field in our side-by-side comparison of the SF850 Platinum and the V850 SFX Gold, and the full power supply category holds the larger ATX models too.

Practical selection notes

An 850 W SFX unit is a decision for a small case with capable hardware. First confirm whether your case takes an SFX power supply directly or needs a bracket, because this page does not mention an adapter. Then count the connectors: three separate PCIe cables, one 12VHPWR cable and two EPS cables cover most single-graphics-card builds, while a system with two cards or many drives will hit limits sooner. The individual sleeving keeps the build tidy but asks for patience when routing, because the short cables leave little slack in a tight case.

What the page does not say

The page does not list dimensions for this unit, hold-up time, the individual protection circuits or any decibel figure, and its price field is tied to a selector with several capacities, so no price is given here. The weight is listed as 2 kg, which is a rounded figure. SFX power supplies usually ship with an SFX-to-ATX bracket, but this page does not mention one, so we make no claim about it; confirm the package contents with Corsair if you plan to use the unit in an ATX case. As always, check the physical fit and the cable lengths against your case before you order.