June 14, 2024

The PlayStation 4 and Xbox One contain a total of eight CPU cores but developers have access to only 6 cores for gaming.  Xbox One team at Microsoft had unlocked the 7th CPU core [shared between game and some OS services] and added a slight overclock, which provided some wins against the PlayStation 4 in heavy CPU-processing scenarios. And it looks like Sony might have followed suit and unlocked the 7th core in their console as well. This is due to an update in the changelogs of the FMOD Audio API, which is a popular audio gaming middleware. 

Firelight Technologies FMOD Studio API
Detailed Revision History11/17/15 1:07:03 – Studio API patch release (build 69 975)Features:

Lowlevel API – When using System :: record start provided the FMOD :: Sound can now be any channel count, up / down mixing will be ormed ashes be necessary.
Lowlevel API – Improved performance or convolution reverb effect when wet is 0 or input goes idle.
Lowlevel API – PS4 – Added FMOD_THREAD_CORE6 to allow access to the newly unlocked 7th core.

According to the above logs, the 7th core is now available for developers to use after Sony added( stealthily I might add ) this new upgrade via a new SDK update.
The two cores which developers could not use were reserved for the OS of the PS4. After the launch, there have been several firmware updates and Sony now believes that it also can run on one core. This is bound to help the PlayStation 4 in CPU intensive games.Sony has not yet been officially confirmed any of this, but you can view the changelog here.