Specs and discussion
|Rated output power||850W @ up to 50°C|
|Power specification||ATX12V 2.3/EPS12 v2.91|
|Efficiency||85% @ 20% load
88% @ 50% load
85% @ 100% load
|80 PLUS certification||Silver*|
|Input voltage (AC)||Auto-ranging 90-264v, 47-63Hz|
|Fan(s)||1 x 140mm|
|Operating temperature range||0-50°C|
|Cable runs (pre-attached)||
24-pin EATX (split)
1 x 6+2 PEG
|Cable runs (modular, flat)||EPS (8-pin)
1 x 6-pin PEG
1 x 6-pin PEG
1 x 8-pin PEG
1 x 8-pin PEG
2 x 4-pin Molex,
2 x SATA
|Max combined 3.3V & 5V output||N/A|
|Dimension (W x H x L)||150 x 86 x 180mm|
Inevitably, the Corsair HX850 shares many of the performance-orientated characteristics as its bigger and more expensive brother, the HX1000W. Both PSUs are based on Channel Well Technology's designs but are heavily modified for better-than-default performance, according to Corsair. Both share a 140mm temperature-controlled, double-ball-bearing fan; are equipped with 105°C-rated capacities; use DC-to-DC conversion for the 3.3V and 5V lines, and are certified for three-way SLI.
Further, the modular cable-runs are flat, good for airflow and aesthetics. We like the fact that the PSUs are rated to a specified wattage with an ambient temperature of up to 50°C, intimating that they can be pushed farther in regular conditions.
There are a few differences between the two, however, reinforcing the fact that they're not the same PSU rebadged as a lower-capacity model. The 750W/850W models use a single 12V source that's shared for the wattage-hungry components, including graphics cards and CPU(s). One benefit of such an approach lies with the ability to provide power to components whose peak usage may well trip many-railed power supplies.
The mid-range models are also 20mm shorter than the HX1000 although the other dimensions remain the same. The warranty, too, is different, as Corsair ramps it up to seven-year cover instead of five. Lastly, the new HX-series PSUs are ATX12V 2.3 compliant, as opposed to ATX12V 2.2, and the main differences pertain to increased efficiency and a slight change to the CPU's 12V requirements for the V2.3 spec.
Do you need a high-wattage PSU?
The main differentiator between PSUs in a certain range is the sustained wattage that they can output - 450W, 550W, 1,000W, for example. Now, even a relatively high-end system, taking in a 3.5GHz-clocked Core 2 Quad and Radeon HD 4870 X2, consumes less than 500W under full load, so why the need for 850W-plus supplies? The reason is two-fold: firstly, adding in another wattage-eating graphics card can supplement some 200W to that figure. Secondly, the rated output for a particular PSU is its long-term sustained output. Should an 850W PSU be required to deliver 450W it will do just that, and should be able to deliver it with the minimum amount of noise and heat when compared to a 500W PSU that's running flat out. As an analogy, should you wish to drive at 90mph, a BMW 530d will cruise rather more comfortably than, say, a Ford Fiesta 1.2LX.