CPU-Z shows 8 cores, but 4 of them are stopped I am using CPU-Z to test basic things about the J7. It reports an Exynos Octa 7580, 8 cores, 8x ARM Cortex-A53 @ 1.5GHz, r0p3, 28 nm.

At all times that I checked, only cores 0-3 are active, and cores 4-7 are stopped. Power saving is disabled.

Is there any way of activating all cores?
Is there any way of at least seeing all of them active, for testing purposes?

I have found a few posts around (here and here) mentioning that it may be the way the phone + OS kernel keep temperature in check, but I am not sure it applies to J7, and if so, how to circumvent it.

PS:
I find some times that my J7 is sluggish, so I wonder why would it have 4 processors idling if they could work (assuming the causes are processing several apps, which could be tackled by assigning different processors).
Is there any way of activating all cores?


You can't.

The hardware is not designed to have all 8 cores active. The reason for this is that this Octacore CPU is actually based on big.LITTLE technology, where there are two sets of four cores: a powerful big cores used for heavy processing (e.g. gaming) and energy efficient LITTLE cores used for low load applications. The system will automatically switch between the two sets depending on system load, but you can't activate all 8 cores at the same time (it'll likely overheat beyond its intended design if you somehow managed to do so).