So I am building my own laptop and my goal is to give it as much desktop performance as possible. Cooling is not a problem since I have already designed a very potent cooling system.

My question is, where do high-end mobile graphics cards like a Ge Force 980M get their power from?
I did quite a lot of research and what I found was that there are three tiers of MXM slots used in laptops. But even the "high-end" slot MXM-III only provides a maximum of 35 watts to the GPU. When I when to look at the GTX 980M's power draw i found that it had a TDP of 122 watts which is not a completely accurate way to measure power draw but shows that the power draw of the GPU is well over 35 watts.

So where do mobile GPU's get their power from?