The fresh iteration of the Exynos family is based around the same ARM big.LITTE architecture. It packs a quartet of ARM Cortex-A15 cores bumped at 1.8GHz and four 1.3GHz Cortex-A7s ticking at 1.3GHz but the key difference is the usage of an 6-core ARM Mali GPU (Mali-T628MP6) instead of the IT PowerVR SGX used in the previous implementation.
The changes brought by the ARM GPU includes General-Purpose computing on Graphics Processing Units (GPGPU) to accelerate complex and computationally intensive algorithms or operations, with APIs such as OpenCL 1.1 & OpenGL ES 3.0 to enable the processing powered requires by high-end complex games.
Taehoon Kim, vice president of System LSI marketing, Samsung Electronics said in a press note, “Demand for richer graphic experiences is growing rapidly nowadays. In order to meet that demand from both OEMs and end users, we developed this processor which enables superb graphical performance without compromising power consumption.”
Here are some of the key specs:
- 4 ARM Cortex-A15 cores with clock speeds up to 1.8 GHz
- 4 ARM Cortex-A7 cores with clock speeds up to 1.3 GHz
- ARM Mali-T628 MP6 6-core graphics
- 2 x 32-bit LPDDR3-1866 memory
On the processor core front, Exynos 5420 does indeed fully support “Global Task Scheduling” (GTS) with 8 independent cores (also known as big.LITTLE MP). The IKS (In-Kernel Switcher) is of course still the norm in the Linux kernel, but the mainline Linux kernel will be configurable to use IKS and GTS soon when Exynos 5420 will hit the production as there is already a reference implementation on Linaro codebases.
TL;DR: All 8 (or any combination) of the big and LITTLE cores can be used simultaneously if Global Task Scheduling is adopted in the Kernel. GTS couldn’t work with Exynos 5410 because Samsung only supported “Cluster granatity” in their SoC kernel. So even IKS can’t run in an optimal manner (at a A7/A15 CPU pair level). We have yet to see if Samsung implements GTS on a per-CPU basis.
The Exynos 5420 SoC also features multiple on-die image compression (MIC) IP block that lowers the total system power when bringing pictures or multimedia from memory to display panel. This feature increases the battery usage time with a high-resolution display such as WQXGA (2500×1600) especially when browsing the web or running multimedia application that requires the frequent screen refresh.
The Exynos 5420 processor also features a memory bandwidth of 14.9 GB/s paired with a dual-channel LPDDR3 at 933MHz, enabling an fast data processing and support for full HD Wifi display. The processor also support hardware video decoding and encoding at 1080p at 60fps. Miscellaneous updates were also made, the VP9 encoder/decoder received some minor tweaks.
As AnandTech pointed out, this revamped SoC should address the broken CCI-400 coherent bus interface that connect the two CPU modules to the rest of the SoC. In the case of the 5410, the bus was functional but coherency was broken and manually disabled on the Galaxy S 4.
This massively plagued the latter and hereby induced decreased battery life since all caches were being flushed out to main memory upon a switch between CPU, it crippled the chip to only cluster migration, effectively making the major parts of the big.LITTLE operating scheme useless. This was a issue at the silicon level which could not be solved via any software/kernel updates.
There’s no word on which devices might use the new SoCs, but the chips are already being sampled by Samsung’s customers, and mass-production is slated for August to debut in new Chromebooks this fall.
The Exynos 5420 could also very well make its way into the upcoming Galaxy Note III if rumors are to be believed!