Up until now, Samsung's 'octa-core' Exynos 5 Octa system-on-a-chip (SoC) hasn't really contained an octa-core CPU. The quad-core ARM Cortex-A15 and quad-core ARM Cortex-A7 CPUs were split, with software choosing which set of cores to use depending on the system load: A15s for intense tasks, A7s for low-power tasks.
Samsung's announcement today joins the two sets of cores together through a Heterogeneous Multi-Processing (HMP) solution, which brings the full benefits of ARM's big.LITTLE architecture to the surface. HMP allows any or all of the eight cores in the SoC to operate simultaneously, allowing device manufacturers to specially purpose cores or core combinations for certain tasks.
While an octa-core chip implementing big.LITTLE without HMP can be reasonably power efficient, in can lag behind a HMP-enabled solution in both performance and power consumption. The Samsung Galaxy S4 i9500 includes a non-HMP Exynos 5 Octa chipset, and it exhibits slight lag when firing up intense tasks, as the system seems to switch from the A7 to A15 cores; performance issues not found in the model with a Qualcomm Snapdragon 600 SoC.
Samsung says their HMP solution for Exynos 5 Octa SoCs will be made available to "customers" in the fourth quarter of this year. Theoretically HMP could be enabled through a low-level device firmware update, although Samsung hasn't confirmed whether this will eventuate for handsets such as the Galaxy S4.
The inclusion of HMP in their eight-core Exynos chipsets makes Samsung the second SoC manufacturer to have made available an actual octa-core ARM chip, where all eight cores can operate at the same time. The first OEM to do so was MediaTek with their "True Octa-Core" MT6592 SoC, although as it only includes ARM Cortex-A7 cores, on paper it appears slower than Samsung's solution.