Despite being a hundred dollars more expensive than PlayStation 4, Xbox One hardware is in fact slightly less powerful than its competitor's. Rumors have it that Microsoft is aware of that fact and is taking measures to change that before launch.
According to the rumors, Microsoft is increasing Xbox One RAM size from 8GB to 12 GB and increasing its GPU clock speed. The company is also collecting developers' feedback regarding changes they wish to see in Xbox One hardware.
A "trusted source" confirmed to Guru3D's Hilbert Hagedoorn that first party developers have already been notified about the GPU clock speed increase. According to him, current projects are too far in development to benefit from the specs bump. It is likely that the first games to utilize those extra clock cycles would be released in 2014.