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Conclusions

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 57° 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 adapters.

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.

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Gabriel Torres is a Brazilian best-selling ICT expert, with 24 books published. He started his online career in 1996, when he launched Clube do Hardware, which is one of the oldest and largest websites about technology in Brazil. He created Hardware Secrets in 1999 to expand his knowledge outside his home country.