Damn it, MS balked at offering Windows on power efficient Atoms. This because Intel had stripped PCI from the SoC to save transistors and thus power.

I suspect that if you were to poke at the ARM chips found in the Windows RT devices, they would be special variants with PCI grafted on.

ARM SOCs are a bit like firing up an old DOS PC and fiddling with IRQ and DMA setting, only that you can't pull the cover off to see what cards are inserted and what the DIPs are set to.