A chief technical expert from Samsung’s Mobile Solutions department announced that Note 3 and S4 won’t be packed with full octa-core in their Exynos chipset. Recently, the company also indicated that the Exynos 5 Octa has a restriction of maximum of four cores.
The engineer comments that the thermal envelope of the Exynos chips hasn’t been cut for the job, 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 . Hence, there might be over-heating issues under pressure which after the Exynos 5 Octa batches get updated with the new methodology that is aimed to avoid this over-heating in octa-core situations. But this fix will not apply to your Note 3 or S4 since they are sporting the current thermal envelopes which are restricted to work on only 4 cores at a time.