While the reference design for the northbridge's TDP is always available in the Technical Documentation (http://support.amd.com/us/ChipsetMotherboard_TechDocs/48691.pdf), there are always slight adjustments that can be made by the motherboard manufacturer regarding power consumption, so contacting the mobo manufacturer is always recommended. But the 13.6W is the standard reference design TDP for the 970 chipset (named RX980 in that document)
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