Suggested wattage for Crossfire

For a system using two AMD reference design Radeon HD 7850 graphics cards in 2-way CrossFireX mode AMD specifies a minimum of an 600 Watt or greater system power supply. The power supply should also have a maximum combined +12 Volt continuous current rating of 39 Amps or greater and have at least two 6-pin PCI Express supplementary power connectors. Some of the non-reference design Radeon HD 7850 graphics cards require at least two 6-pin PCI Express supplementary power connectors for each graphics card so the power supply should have at least four 6-pin PCI Express supplementary power connectors.

Total Power Supply Wattage is NOT the crucial factor in power supply selection!!! Sufficient Total Combined Continuous Power/Current Available on the +12V Rail(s) rated at 45°C - 50°C ambient temperature, is the most critical factor.

Overclocking of the CPU and/or GPU(s) will require an additional increase to the maximum combined +12 Volt continuous current ratings, recommended above, to meet the increase in power required for the overclock. The additional amount required will depend on the magnitude of the overclock being attempted.

The Seasonic X-Series X-650 (SS-650KM3), with its maximum combined +12 Volt continuous current rating of 54 Amps and with four (6+2)-pin PCI Express supplementary power connectors, is way more than sufficient to power your system configuration with two Radeon HD 7850 graphics cards in 2-way CrossFireX mode.