The Intel RealSense SDK states the requirements as Windows 8.1 (64 bits), and 4th generation Core processor.
I have noticed though, that these requirements seem to only apply to parts of the SDK, specifically the gesture detection/tracking. Some other features are still available, such as raw depth, IR, and color streams, and speech recognition and text to speech (and probably face recognition and emotion recognition as well).
I have tested the camera on a very limited machine, an Asus T100 with win8.1 32 bits (Atom CPU), and those bits of the SDK seem to work fine there. I am streaming depth data from the camera to OpenCV, and it works fine.
