Looking at http://www.phoronix.com/scan.php?page=article&item=samsung_exynos5_dual&num=1 a 4 core A15 SoC provides sufficient compute power even for more than 80% of all commercial desktop needs. Future will be interesting ...
If OS supports the multi processing mode of big.LITTLE technology, then yes, APP can access all eight cores.
You bet they can! Think real-time image/data processing and data collection tasks. I have applications that consume all of my dual-core processing right now and could use more. The issue, now, is power consumption (how long can I run on all four cores going at full speed) and memory bandwidth (can my portable device's memory feed all those processors fast enough to keep them running at full speed).
My understanding is that in standard big-little operation the operating system sees just four cores.
As load increases applications move up through the dynamic voltae and clock frequency scaling (DVFS) on the A7 until it is close to maximum then they are moved on to the low-end of the DVFS for for the companion A15 where the scaling continues to maximum voltage and clock frequency. As the processing load reduces the reverse happens.
There is not much latency in switching from A7 to A15 but it is still important to avoid a hysteresis effect where the software repearedly bounces from A7 to A15 and back.
This is Quad Core SoC, not Eight Core. In Peak performance mode, it will be only Quad A15 running. A7 only kicks in at low power mode to replace shutting down A15. Nvidia Tegra 4 claims to be Quad Core SoC but I am sure there is similar Big-Little arrangement to have 4 Low Power Cores behind.
No, he's right. There are 5 cores, but it's only a "quad core" chip, with a companion core being activated for low-end tasks (while deactivating the other 4).
So it's very similar to Samsung's Exynos 5 Octa, although I have serious doubts that the low-clocked A15 is more energy efficient than a quad core A7.
big.LITTLE supports three operation modes. Cluster migration, CPU migration, and multi processing mode. In multi processing mode, all four A7 cores and four A15 cores are on at any time.
SAMSUNG's new exynos chip also supports all of those three modes.
Check out the ARM website.
You're right, but I doubt all cores will be used except for very specific applications meant to take advantage of it - like any app that could take advantage of heterogeneous computing.
The rest 99.9% of them will only use 4 cores at most.
Well, that has to be the main application target, isnt't it? If Samsung wanted to have just more power, they would have not bothered with the big-little implementation. They would have used eight full-speed, full-power cores, all active at the same time and with the usual clock scaling. This seems to be a sensible compromise, two distinct, selectable computational levels, each optimized for different operational conditions, plus the option to combine both to have higher processing power when really needed.
Thanks for information for Nvidia Core.
I am surprised that my comments cause so much discussion. I will agree that nothing prevent all 8 cores running at the same time although it is not likely choice. A7 performance per MHz is only half of A15 and is running at 60% of clock frequency. Therefore, each A7 core will only deliver 1/3 A15 performance. So it doesn't make lots of sense to allow A7 join A15 cluster in most cases. Therefore, its performance is only equivalent to 5.3 A15 Core performance. So we should call Samsung 5.3 Core in the future. :-)
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