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.