If your title does not utilize NUI title speech, we recommend that you enable the 7th processing core in order to gain access to additional processing power and to reduce underlying system overhead from the NUI title speech engine.
Enabling the 7th Processing Core
Access to the 7th core is enabled by setting the XboxSystemResources extension to 'extended' in the application package manifest.
Note that process lifetime management states will continue to operate at current levels. For example, when your application becomes constrained it will be limited to 4 CPU cores. When your application is suspended it will have access to 0 CPU cores. The 7th core is only available when your application is in the full state. As a consequence of disabling NUI title speech, other NUI services such as IR and depth are also disabled. Because of this, titles making use of the 7th core should also set the CoreApplication.DisableKinectGpuReservation property to true in order to make use of the 4.5% NUI GPU reserve.
Windows::ApplicationModel::Core::CoreApplication:
isableKinectGpuReserve = true;
Availability of the 7th Core
Because the 7th core is shared with the underlying system OS, titles will not be able to utilize 100% of the core. Titles are always guaranteed at least 50% of the core and will have at most 80% of the core. The amount of the core that is available will vary based on what is happening in the system at any point in time. For example, when the system must process commands spoken by the user (e.g "Xbox Go To Friends"), it will take up to 50% of the 7th core. After the processing is done, the amount of the core made available to the title will increase again, up to the maximum of 80%."
source: the chm file that was also leaked.
