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For a system using a reference clocked single Radeon HD 7850 graphics card AMD specifies a minimum of a 500 Watt or greater power supply. The power supply should also have a combined +12 Volt continuous current rating of 26 Amps or greater and have at least one 6-pin PCI Express supplementary power connector.

For a system using two Radeon HD 7850 graphics cards in 2-way CrossFireX mode AMD specifies a minimum of an 600 Watt or greater power supply. The power supply should also have a combined +12 Volt continuous current rating of 36 Amps or greater and have at least two 6-pin PCI Express supplementary power connectors.

Total Power Supply Wattage is NOT the crucial factor...
For a system using a reference clocked single Radeon HD 7850 graphics card AMD specifies a minimum of a 500 Watt or greater power supply. The power supply should also have a combined +12 Volt continuous current rating of 26 Amps or greater and have at least one 6-pin PCI Express supplementary power connector.

For a system using two Radeon HD 7850 graphics cards in 2-way CrossFireX mode AMD specifies a minimum of an 600 Watt or greater power supply. The power supply should also have a combined +12 Volt continuous current rating of 36 Amps or greater and have at least two 6-pin PCI Express supplementary power connectors.

Total Power Supply Wattage is NOT the crucial factor in power supply selection!!! Total Continuous Amperage Available on the +12V Rail(s) is the most important factor.

The Corsair Builder Series CX600 V2 (CMPSU-600CXV2), with its combined +12 Volt continuous current rating of 40 Amps and with two (6+2)-pin PCI Express supplementary power connectors, is more than sufficient to power your system configuration with a single Radeon HD 7850. It is also sufficient to power your system configuration with two Radeon HD 7850 in 2-way CrossFireX mode.
 
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