Oculus recently revealed that they are working on a technology which is going to lower the PC specs needed to handle Oculus Rift.
The new technology is called Asynchronous Spacewarp, and despite sounding like something straight out of Star Trek, it’s quite real, and quite useful. As the developers put it: “Asynchronous Spacewarp (ASW) is a frame-rate smoothing technique that almost halves the CPU/GPU time required to produce nearly the same output from the same content”.
The full technical explanation for how it works can be read on developer blog, but it all seems sound.
Asynchronous Spacewarp (ASW) helps lower-end PCs, but it still has certain hardware requirements: “The hardware requirements for ASW are modest. This functionality has been enabled on all current-generation AMD GPUs (RX 400 series) and previous- or current-generation Nvidia GPUs (GTX 900 or 1000 series)”.
As for the OS, Windows 8 is enough, but Windows 10 has the best support.