http://www.eurogamer.net/articles/d...es-more-cpu-power-to-xbox-one-developers-blog
Up until recently, both Xbox One and PlayStation 4 have reserved two entire CPU cores (out of eight available) in order to run the background operating system in parallel with games. Since October, Microsoft has allowed developers access to 50 to 80 per cent of a seventh processing core - which may partly explain why a small amount of multi-platform titles released during Q4 2014 may have possessed performance advantages over their PS4 counterparts in certain scenarios.
However, there's no such thing as a free lunch, and the additional CPU power comes with conditions and trades attached - however, there is the potential for many games to benefit. Firstly, developers need to give up custom, game-specific voice commands in order to access the seventh core at all, while Kinect's infra-red and depth functionality is also disabled. Secondly, the amount of CPU time available to developers varies at any given moment - system-related voice commands ("Xbox record that", "Xbox go to friends") automatically see CPU usage for the seventh core rise to 50 per cent. At the moment, the operating system does not inform the developer how much CPU time is available, so scheduling tasks will be troublesome. This is quite important - voice commands during gameplay will be few and far between, meaning that 80 per cent of the core should be available most of the time. However, right now, developers won't know if and when that allocation will drop. It's a limitation recognised in the documentation, with Microsoft set to address that in a future SDK update.
It's an interesting theory, but the timing of the presentation (August 2014 - two months before the new feature was added to the SDK) suggests not. Speaking to a prominent developer, one potential explanation is that differences in code compiler efficiency might favour Microsoft's console right now. How the availability of a seventh processing core will affect game performance going forward remains to be seen. Certainly, the whole point of Ubisoft's presentation is that moving CPU tasks to GPU is the future, and in this respect, it is the PS4 that is in the driving seat. Based on the single example Ubisoft's presentation provides (and it's worth stressing that all of these numbers are derived from just one piece of code), PS4 is almost twice as fast.