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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 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.

https://forums.oneplus.net/threads/cpu-z-4-core-stopped.435432/

https://forums.oneplus.net/threads/2-cpu-cores-dont-work-at-all.420496/#post-14352587

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).

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That is perfectly fine. Why would 8 cores be active if you are in cpu-z app. Four cores are let's say active all time, and other four are jumping in if needed, cpu-z don't need 8 cores trust me. Try runing some heavy process like video convertor or unziping huge file, and in time of converting/unziping open cpu-z and see.

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It all depends on how the apps that are running are written and if they can actually make use of multiple cores. Even if you are running a heavy application, if it cant make use of all the cores, the other cores might still be appearing as off. Most system apps these days can use all the cores that the hardware has to offer. Bottom Line: You do not at all need to worry about number of cores running. Let OS do its thing!

  • Do you know of any specific app that one could use to see the 8 processors running? – sancho.s Feb 13 '17 at 7:16
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Actually the core usage depends on the usage of particular apps. Like, if you use high graphics game you'll usually find that the number of core in use are more whereas if you use simple applications like WhatsApp Messenger the number of core in use will be 3-4 maximum. Hope it helped you.

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If you switch to other apps and then back to CPU-Z, you would briefly see all the cores working.

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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).

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Yep, same here thought which brought me here but then noticed also if you fire few apps and then switch between these and back to CPU-z it will shortly show activity on all cores.

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