Conceptually, it's just like Windows 8 can run both on a desktop as well as a Lumia phone. I'm not sure whether they actually share parts of the codebase (like the linux kernel does), or it's just some common UI elements like tiles + shared brand name on top of wildly different kernels.
"...the Windows Phone OS will include the same file system (NTFS), same networking stack, same security elements, graphics engine (DirectX), device driver framework and hardware abstraction layer (HAL) as big Windows."
I hadn't realized they share so much. If this statement holds true for the upcoming Windows 10, then it's probably the very first time DirectX is running on any SBC. I wonder if Broadcom have made some changes to VideoCore GPU to support DirectX.
