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

).