Corsair HX850W is a power supply with modular cabling system and high-end components promising up to 90% efficiency, launched to compete with Antec Signature series and Seasonic M12D series.
It is very important to notice that Corsair HX750W, HX850W and HX1000W have nothing to do with other models from this same series. They use a complete different (and better, by the way) design using a DC-DC converter to generate their +5 V and +3.3 V outputs, like Antec Signature series and Seasonic M12D series. These HX models are manufactured by CWT, while other models from HX series are manufactured by Seasonic. Why Corsair kept the same name is a mystery. In our opinion they should have used a different name so consumers would know they are facing a different product class, targeted to users looking a power supply with high-end parts and very high efficiency.
Corsair HX1000W uses two transformers inside, while HX850W and HX750W use only one.
HX850W is somewhat long, being 7 3/32” (18 cm) deep, using a 140-mm fan on its bottom and featuring active PFC, of course. It also features a single-rail design.
It comes with a modular cabling system, but the main motherboard cable (20/24-pin), the ATX12V/EPS12V cable (two ATX12V connectors that together form an EPS12V one) and two six/eight-pin auxiliary power cable for video cards come from inside the unit. These cables are protected with nylon sleevings that come from inside the power supply housing.
The modular cabling system has ten connectors and HX850W comes with ten cables plus two adaptors to convert standard peripheral power plugs into floppy disk drive power plugs. The cables included are:
Four auxiliary power cables for video cards, with one six/eight-pin connector on each one of them.
Three SATA power cables with four plugs each.
Three peripheral power cables with four plugs each.
The number of cables and connectors available is really impressive. With six auxiliary power connectors for video cards you can easily install up to three very high-end video cards under SLI mode without using any kind of adaptor (each video card from this class requires two auxiliary power connectors).
The main motherboard cable, the ATX12V/EPS12V cable and the video card cables are long, measuring 23 5/8” (60 cm), so you probably won’t have any trouble using this power supply on a big full tower case. Peripheral and SATA power cables have a distance of 15 ¾” (40 cm) between the end that goes on the power supply and the very first connector on the cable. The distance between each connector on these cables is of 5 1/8” (13 cm).
The main motherboard cable use 16 AWG wires, which are thicker, while all other wires are 18 AWG, which is the correct gauge to be used.
Corsair HX850W is an impressive power supply, being to this date the power supply with the highest efficiency that we’ve ever tested, beating Seasonic M12D 750 W and Antec Signature 650 W.
The reason why these three models achieved 90% efficiency lies on the chosen design. Instead of having separated rectifiers for each output, these three power supplies produce mainly only one output: +12 V. From this +12 V output two smaller power supplies produce the +5 V and +3.3 V outputs. This is what the manufacturer calls “DC-DC design”, although technically the use of this name itself doesn’t make any sense, as all switching power supplies are DC-DC converters (as they increase and convert the wall voltage into DC before sending to the switching transistors).
Not only this design proved to be superior, but Corsair/CWT decided to use only high-end components inside this unit, which features only Japanese capacitors and solid caps on the DC-DC converters in charge of the + 5 V and +3.3 V outputs.
Voltage stability was another highlight, with all voltages within 3% from their nominal values, i.e. we saw voltages closer to their nominal values than what allowed by the ATX standard, which specifies a 5% tolerance (10% for -12 V).
We could also pull up to 1,000 W at 57º C from this unit, which is really impressive.
The number of cables available is impressive (12 SATA power connectors, 12 peripheral power connectors and six six/eight-pin video card power connectors), allowing you to build a very high-end system with three very high-end video cards without the need of using adaptors.
Pricing for this power supply (USD 190) isn’t bad for a superior product, costing less than Seasonic M12D 750 W (USD 210).
The seven-year warranty – probably the highest in the industry – is also another reason to pick this product over competitors.
Corsair HX850W is a very good choice for the very high-end user that wants a power supply with the best internal components and very high efficiency.
