Nabbed from GAF:
Since launch of PS4 we had many reports from devs that games on PS4 can access only 6 CPU cores, while the other two were dedicated to OS. Here is one of them from GG and their postmortem on making launch game Killzone Shadowfall [full PDF]:
In effort of trying to get at least some performance back against PS4 that took commanding lead with 50% stronger GPU and more dev-friendly memory system, Xbox One team at MS unlocked 7th CPU core and added a slight overclocking, which has over the last year provided some wins against PS4 in heavy CPU-processing scenarios. Now it looks like Sony has updated its SDK [as quietly as always] and enabled their developers to also access 7th CPU core. Proof comes from the changelog of the recent update of FMOD, a popular audio gaming middleware.
http://www.neogaf.com/forum/showthread.php?t=1146956
The PS5 Exists.
