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Or they could simply partner with Intel as if AMD used there own chipset this could push the two together
They would still need the 64Bit licence from AMD.
They would get it through Intel, the same as AMD get the x86 license from Intel in order to be able to use the x86_64 feature. Its like ever decreasing circles
Edit: I would just like to add that I do not think any of this would happen, just pie in the sky stuff.
Yes and that is why Nvidia would have to work under Intel, Intel supply the chipset and interconnects to work on a Nvidia card based system. But as you say we have No idea what the license agreements are and it would never happen anyway for all sorts of reasons.