>>/165664/
Same

 >>/165666/
It's not that it's not possible. The architecture is still alike, so the driver will still fallback to a path that is most representative of the hardware.
But custom performance patches some that might also be upstream that targets that specific chip, are lost.
But I see how that'd benefit Valve too. If the machine runs faster and smoother using SteamOS than with Windows, then people won't be blaming the hardware