Galaxy S4 I9500 Exynos Octa Core running sub-optimal Firmware
Samsung might just have released the Galaxy S4 I9500 (Exynos Octa Core version) with a sub-optimal kernel (lower level firmware) probably in a hurry to meet the launch date and market demands. What this really means is that the phone can be expected to both perform better and deliver better battery life with future updates.
As per the famous Samsung based Open Source Community Developer AndreiLux, who recently got his Samsung Galaxy S4 I9500 and has released some amazing custom firmwares(kernels/ROMs) for the Galaxy range in the past, the CPU presently shifts all 4 cores between the two Quad Core CPUs ((Read Octa core) like a cluster instead of the more optimal core-pair shifting.
What this essentially does is, cause excess battery drain every time the high performance CPU is activated. The reason why some people are finding their phones heating up too much, or facing severe battery drain could also be attributed to this.
Lets hope Samsung releases the new updates soon. In a time where the market leader is already facing stiff competition from the HTC One and Sony Xperia Z, alongwith several design critics unhappy with the plastic body, Samsung does not want another reason for people to move over to the competition.
For Advanced Users
The Big.LITTLE Architecture Explained: Source: LWN.net
The Samsung Exynos5 Octa Core Processor is actually a Big.LITTLE CPU Architecture. The Cortel A7 Quad is the LITTLE processor(Less power consumption, Less performance) and the A15 is the Big processor.
Big.LITTLE incorporates architecturally similar CPUs that have different power and performance characteristics. The similarity must consist of a one-to-one mapping between instruction sets on the two CPUs, so that code can “migrate seamlessly”. Identical CPUs are grouped into clusters.
IKS (In kernel Switching) is meant to provide a “solution for now”, he said, one that can be used to build products with. The basic idea is that one A7 and one A15 are coupled into a single virtual CPU. Each virtual CPU in the system will then have the same capabilities, thus isolating the core kernel from the asymmetry of big.LITTLE. That means much less code needs to change.
How to check for IKS:
If you are an advanced user and have rooted your phone, you could check if your current firmware supports In-kernel Switching (Optimal switching of CPU). Here’s how:
You need to navigate to /sys/devices/system/cpu/cpufreq/iks-cpufreq/ using a root explorer of your choice, or using ADB from your computer. If a file named max_eagle_count is present, your phone contains optimal IKS driver, else its running sub-optimal drivers.
The expected impact should be negligible in terms performance, however the battery life could be expected to drop when CPU intensive applications are used. We hope Samsung releases fixes soon.