Note 3 and Galaxy S4 won't be getting the full eight core Exynos performance patch, says Samsung

The thing is, the engineer comments, that even though Samsung can release a software patch that will allow both the quad-core Cortex-A15 set, and the frugal Cortex-A7 cores, to get together for a task, the thermal envelope of these Exynos chips hasn't been cut for the job. 

Thus there might be issues with heat dissipation under pressure, and it's only after the Exynos 5 Octa batches get updated with new production methodology aimed to avoid overheating in octa-core scenarios, that Samsung will unlock this ability. Since your Note 3 and Galaxy S4 are sporting the current thermal envelopes, calculated to run with only four cores at once, the fix won't apply to them, at least officially, unless you don't mind the risk of frying your handset.

On the issue of the Android 4.4 KitKat update for Samsung's flagships, the expert advised that this is still months away, and right now they are focusing on getting Android 4.3 rolled out to everyone in Q4.

source: Hi-tech.mail.ru