I believe they said that the 1DX sensor used some new technology.
Canon states, "A new photodiode structure with an increased photoelectric conversion rate increases the sensor's sensitivity by approximately 2 stops over previous models, meaning higher ISOs with the lowest noise of any EOS digital camera.
" When you dissect that statement, it says they boosted the native ISO by two stops. You could get that from the specs (1D IV is 100-12,800, 1D X is 100-51,200). They don't
say the noise is the same at an ISO that's two stops higher. Elsewhere, they claim 2 stops better noise than the 1D IV, but Chuck Westfall admits that's mostly NR with in-camera JPG conversion - and that's compared to a smaller sensor. The theoretical difference between 1.3x and FF is ~2/3-stop of ISO noise.
What I'm personally interested in for the 'new sensor technology' whatever that is exactly, is how high-ISO RAW files from the 1D X compare to the 5DII. If it's a stop better, I'll be quite pleased.
The implication is that assuming those improvements trickle down to the APS-C format, we'll see an improvement there, and likely in a G2X as well (trying to get back on topic here